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Of Mice and Men
Fever in an elderly man is a nonspecific finding, occurring most commonly with infections but also with certain malignancies, rheumatologic disorders, and drug exposures. The complaint of rigors with diaphoresis makes an infection most likely. The acuity of his illness makes infections with more chronic presentations such as tuberculosis or actinomycosis less likely. The presence of frontal headache might suggest a sinus or brain source, but headache also occurs in generalized infections such as pneumonia, bacteremia from any cause, malaria, rickettsial infections, viral illnesses, and others. Additional history should include detailed inquiry into travel, vocational, and avocational exposures.
The patient's difficulty standing implies the development of lower extremity weakness and infections associated with neurological syndromes. His leg weakness may be related to early Guillain‐Barre syndrome, which is associated most commonly with Campylobacter jejuni, but also other bacteria and viruses such as Haemophilus influenza, Mycoplasma pneumonia, Influenza virus, Cytomegalovirus and hepatitis E. Other viral infections associated with pure motor deficits include echovirus, coxsackie virus, enterovirus, and West Nile virus (WNV). The paralytic syndrome associated with enteroviruses is more common in children, whereas the neuroinvasive variant of WNV more often affects the elderly and can be associated with encephalitis as well as a flaccid paralysis. Although acute paralytic shellfish poisoning could account for both his weakness and his acute gastrointestinal syndrome, this diagnosis is unlikely because the symptoms often have a prominent sensory component, and there is usually the history of recent ingestion of the suspect bivalves. Like all adults presenting for medical care, he should be screened for human immunodeficiency virus (HIV) infection; if testing is positive, the differential diagnosis for his current illness broadens significantly. Finally, he may have a spinal cord disorder or infection such as an epidural abscess, or transverse myelitis, which would present with lower extremity weakness and fever. It would be helpful to know the time of year of his illness, exposure to mosquito bites, his neurological exam findings, and results of blood and stool cultures. If the patient had signs of meningitis or encephalitis, cerebral spinal fluid analysis would be helpful. If his neurological exam was suggestive of cord involvement, it would be helpful to know the results of magnetic resonance imaging of the spinal cord.
The patient's past medical history includes relatively common problems for a 73‐year‐old man and does not substantially influence the differential diagnosis of his current illness. His travel history to Uganda a year previously may be relevant, because malaria (Plasmodium vivax) could present with fever and weakness. Less commonly, African trypanosomiasis (Trypanosoma brucei gambiense) can, in the late phase, present with fever and malaise, but also typically includes symptoms of encephalitis, including depressed mental status, confusion, ataxia, and possibly personality changes. His travel to Zurich should not impose any particular infection risk, unless he was hiking in the mountains around Zurich, where he could have contracted tick‐borne encephalitis; however, his travel more than 6 months prior to presentation makes this unlikely. Lyme disease due to Borrelia burgdorferi is also a potential exposure in the Swiss mountains, and can present with fever in the acute phase, as well as arthritis with chronic disease, but should not cause fever, rigor, diaphoresis, and headache many months later. Summering in Cape Cod puts him at risk for babesiosis, but an incubation period of 5 months is too long. Keeping chickens places him at risk for Salmonella exposure and typhoid fever. Ingesting raw oysters carries a risk for shellfish poisoning and Vibrio infections, but the incubation period (1 month) again seems too long to cause his current symptoms.
Notable physical findings are an ill‐appearing man with injected sclera and a high fever but normal blood pressure and heart rate. He also demonstrates proximal lower extremity weakness manifested by difficulty rising from a chair and a slow gait with short strides and deliberate (possibly on‐block) turning. His neurological exam is most consistent with Parkinsonian symptoms that have been described in patients with severe influenza A, which would explain all of his other symptoms as well. Pulse‐temperature dissociation is classically described with typhoid fever but usually occurs later in the disease course, and could be masked by the patient's metoprolol. Typhoid fever can also be associated with neurological symptoms including meningitis and movement disorders.
The patient has a remarkable bandemia, suggesting a bacterial infection, as well as a slight reduction in hematocrit and platelet count. Additionally, his labs revealed a mild transaminitis, but with significantly elevated alkaline phosphatase and GGT, and microscopic hematuria. His ferritin is significantly elevated, which may simply represent an acute phase reactant. Infections associated with hepatitis, cytopenias, and hematuria include sepsis with disseminated intravascular coagulation, previously mentioned malaria, leptospirosis, dengue, ehrlichiosis, and rickettsial diseases, but he has no special risks for these infections, and other aspects of his illness (Parkinsonian features, bandemia) do not fit. His lung findings with hematuria might suggest a pulmonary/renal syndrome, but, once again, other features of his illness are not typical of these syndromes. Salmonella (typhoid fever) or influenza, now complicated by an early bacterial pneumonia, are viable possibilities.
The patient's ongoing clinical course is notable for a nontoxic (non‐SIRS) appearance but continued high‐grade fever with blood and urine cultures that are sterile. This argues against a common bacteremia with sepsis, and for either relapsing malaria (P vivax), influenza with a Parkinsonian‐like illness, typhoid fever, leptospirosis, dengue, or a rickettsial infection. Mycoplasma pneumonia is also possible given the atypical chest x‐ray appearance, slightly low hematocrit with elevated bilirubin, and neurological symptoms that may represent ataxia.
The subsequent negative laboratory tests listed are helpful in likely excluding many of the diagnoses suggested such as malaria, Babesia, common bacteremias, viral hepatitis, HIV, and WNV. Furthermore, the new history of mouse exposure brings to the forefront rodent‐associated infections, specifically exposure to mouse urine, a vehicle for leptospirosis. The patient's hepatitis, anemia, thrombocytopenia, scleral injection, along with the rest of his symptoms in the context of exposure to mouse urine makes leptospirosis the likely diagnosis. A negative Leptospira antibody early in his illness does not rule out the disease, and a convalescent titer should be obtained to confirm the diagnosis.
COMMENTARY
This case describes an elderly man who presented with a fever of unknown origin (FUO), and was eventually diagnosed with leptospirosis. FUO presents slightly differently in elderly patients, as elderly patients are less likely to mount a high fever, and when they do, the etiology is more likely to indicate a serious bacterial or viral infection. Additionally, an etiology for FUO in the elderly is found in over 70% of presenting cases, compared to 51% in patients under the age of 65 years.[1] A detailed, comprehensive social, travel, and exposure history and physical examination remains the cornerstone of elucidating the diagnosis for FUO. The exposure to mouse urine in this case was an unusual and a helpful piece of the history to further focus the differential diagnosis.
Leptospirosis is an emerging bacterial zoonosis, and causes both endemic and epidemic severe multisystem disease. The Leptospira spirochete is maintained in nature through a chronic renal infection in mammalian reservoir hosts, such as mice,[2, 4] and is transmitted through direct or aerosolized contact with infected urine or tissue. After a mean incubation period of 10 days, a variety of clinical manifestations may be seen. In this case, the patient's clinical presentation revealed many classic symptoms of leptospirosis, including fevers, rigors, headache, lower extremity myalgias, nausea, vomiting, and diarrhea; however, these symptoms are nonspecific. The presence of a conjunctival suffusion in leptospirosis infection had a specificity of 98% in a high‐incidence cohort of febrile patients in Sri Lanka,[3] and was an important diagnostic clue in this case. Leptospirosis is a self‐limited illness in most patients, with an initial septicemic, febrile phase followed by an immune phase. A more severe presentation may be seen in the immune phase of the illness, which includes renal and hepatic dysfunction (known as Weil's disease), as well as cardiac, pulmonary, and central nervous system abnormalities. With a 14% case fatality rate, the risk of death has been shown to be higher in patients over 40 years old, with altered mental status and multiorgan failure.[4]
The early diagnosis of leptospirosis relies heavily on physical exam findings and epidemiologic history. In this case, the patient's laboratory abnormalities, including immature granulocytes, thrombocytopenia, hyponatremia, hypokalemia, mild hepatitis, and pyuria with granular casts are all reported with leptospirosis infection2; however, independently, these laboratory findings are nonspecific. Patients may not have a detectable antibody levels in the acute phase of the disease. In this case, given the strong clinical suspicion based on the findings of conjunctival suffusion and exposure to mouse urine history, the lack of a more plausible alternate diagnosis, and known delay in antibody positivity, the patient was treated empirically with doxycycline for presumed leptospirosis.[5] Forthcoming novel diagnostic strategies such as next‐generation DNA sequencing techniques may provide real‐time diagnosis of this zoonotic infection, thus decreasing the window period between empirical antimicrobial coverage and diagnostic confirmation.[6]
Leptospirosis is prevalent in tropical climates and has been associated with impoverished communities.[7] Urban slums, with poor sanitation and high rodent density, are an ideal environment for leptospirosis. The reported risk of infection in a Brazilian slum was as high as 3% per year.[8] Additionally, rodent sightings, as well as the presence of chickens, were risk factors for leptospirosis transmission in urban slums.[9] Correspondingly in this case, we hypothesize that the patient's interest in urban farming, specifically the chickens he kept, likely attracted the mice infected with leptospirosis. Urban chicken farming is becoming increasingly popular in the United States,[10] and may be a developing risk factor for human leptospirosis infection. Leptospirosis is one of many emerging zoonoses, such as avian influenza, tick‐borne illness, and ebola, resulting from changing human ecology. Thus, when considering infectious etiologies, clinicians should ask patients about vocational and avocational exposures, including new trends such as urban farming, which may expose them to previously underappreciated illnesses.
TEACHING POINTS
- Elderly patients with a FUO are more likely to be diagnosed with an underlying serious bacterial or viral infection when compared to a younger cohort of FUO patients.
- The diagnosis of leptospirosis may initially be based on clinical suspicion in patients with classic features and exposures, noting the high specificity of conjunctival suffusion, and initial titers may be nondiagnostic; therefore, empiric treatment should be considered when clinical suspicion is high.
- Increased interest in urban chicken farming in the United States, with associated higher rodent density, may represent a newly recognized risk factor for human leptospirosis infection.
Disclosures
The authors report no conflicts of interest.
- Fever of unknown origin in older persons. Infect Dis Clin North Am. 2007;21(4):937–945. , , .
- Leptospirosis. Clin Microbiol Rev. 2011;14(2):296–326. .
- Leptospirosis as frequent cause of acute febrile illness in southern Sri Lanka. Emerg Infect Dis. 2011;17(9):1678–1684. , , , et al.
- Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Philadelphia, PA: Elsevier; 2010. , , , et al.
- Antibiotics for leptospirosis. The Cochrane Database Syst Rev. 2012;2:CD008264. , .
- Actionable diagnosis of neuroleptospirosis by next‐generation sequencing. N Engl J Med. 2014;370(25):2408–2417. , , , et al.
- Cases distribution of leptospirosis in City of Manaus, State of Amazonas, Brazil, 2000–2010. Rev Soc Bras Med Trop. 2012;45(6):713–716. , , , .
- Prospective study of leptospirosis transmission in an urban slum community: role of poor environment in repeated exposures to the leptospira agent. PLoS Negl Trop Dis. 2014;8(5):e2927. , , , et al.
- Impact of environment and social gradient on leptospira infection in urban slums. PLoS Negl Trop Dis. 2008;2(4):e228. , , , et al.
- Urban chicken ownership in four U.S. cities. United States Department of Agriculture website. Available at: http://www.aphis.usda.gov/animal_health/nahms/poultry/downloads/poultry10/Poultry10_dr_Urban_Chicken_Four.pdf. Published April 2013. Accessed June 9, 2015.
Fever in an elderly man is a nonspecific finding, occurring most commonly with infections but also with certain malignancies, rheumatologic disorders, and drug exposures. The complaint of rigors with diaphoresis makes an infection most likely. The acuity of his illness makes infections with more chronic presentations such as tuberculosis or actinomycosis less likely. The presence of frontal headache might suggest a sinus or brain source, but headache also occurs in generalized infections such as pneumonia, bacteremia from any cause, malaria, rickettsial infections, viral illnesses, and others. Additional history should include detailed inquiry into travel, vocational, and avocational exposures.
The patient's difficulty standing implies the development of lower extremity weakness and infections associated with neurological syndromes. His leg weakness may be related to early Guillain‐Barre syndrome, which is associated most commonly with Campylobacter jejuni, but also other bacteria and viruses such as Haemophilus influenza, Mycoplasma pneumonia, Influenza virus, Cytomegalovirus and hepatitis E. Other viral infections associated with pure motor deficits include echovirus, coxsackie virus, enterovirus, and West Nile virus (WNV). The paralytic syndrome associated with enteroviruses is more common in children, whereas the neuroinvasive variant of WNV more often affects the elderly and can be associated with encephalitis as well as a flaccid paralysis. Although acute paralytic shellfish poisoning could account for both his weakness and his acute gastrointestinal syndrome, this diagnosis is unlikely because the symptoms often have a prominent sensory component, and there is usually the history of recent ingestion of the suspect bivalves. Like all adults presenting for medical care, he should be screened for human immunodeficiency virus (HIV) infection; if testing is positive, the differential diagnosis for his current illness broadens significantly. Finally, he may have a spinal cord disorder or infection such as an epidural abscess, or transverse myelitis, which would present with lower extremity weakness and fever. It would be helpful to know the time of year of his illness, exposure to mosquito bites, his neurological exam findings, and results of blood and stool cultures. If the patient had signs of meningitis or encephalitis, cerebral spinal fluid analysis would be helpful. If his neurological exam was suggestive of cord involvement, it would be helpful to know the results of magnetic resonance imaging of the spinal cord.
The patient's past medical history includes relatively common problems for a 73‐year‐old man and does not substantially influence the differential diagnosis of his current illness. His travel history to Uganda a year previously may be relevant, because malaria (Plasmodium vivax) could present with fever and weakness. Less commonly, African trypanosomiasis (Trypanosoma brucei gambiense) can, in the late phase, present with fever and malaise, but also typically includes symptoms of encephalitis, including depressed mental status, confusion, ataxia, and possibly personality changes. His travel to Zurich should not impose any particular infection risk, unless he was hiking in the mountains around Zurich, where he could have contracted tick‐borne encephalitis; however, his travel more than 6 months prior to presentation makes this unlikely. Lyme disease due to Borrelia burgdorferi is also a potential exposure in the Swiss mountains, and can present with fever in the acute phase, as well as arthritis with chronic disease, but should not cause fever, rigor, diaphoresis, and headache many months later. Summering in Cape Cod puts him at risk for babesiosis, but an incubation period of 5 months is too long. Keeping chickens places him at risk for Salmonella exposure and typhoid fever. Ingesting raw oysters carries a risk for shellfish poisoning and Vibrio infections, but the incubation period (1 month) again seems too long to cause his current symptoms.
Notable physical findings are an ill‐appearing man with injected sclera and a high fever but normal blood pressure and heart rate. He also demonstrates proximal lower extremity weakness manifested by difficulty rising from a chair and a slow gait with short strides and deliberate (possibly on‐block) turning. His neurological exam is most consistent with Parkinsonian symptoms that have been described in patients with severe influenza A, which would explain all of his other symptoms as well. Pulse‐temperature dissociation is classically described with typhoid fever but usually occurs later in the disease course, and could be masked by the patient's metoprolol. Typhoid fever can also be associated with neurological symptoms including meningitis and movement disorders.
The patient has a remarkable bandemia, suggesting a bacterial infection, as well as a slight reduction in hematocrit and platelet count. Additionally, his labs revealed a mild transaminitis, but with significantly elevated alkaline phosphatase and GGT, and microscopic hematuria. His ferritin is significantly elevated, which may simply represent an acute phase reactant. Infections associated with hepatitis, cytopenias, and hematuria include sepsis with disseminated intravascular coagulation, previously mentioned malaria, leptospirosis, dengue, ehrlichiosis, and rickettsial diseases, but he has no special risks for these infections, and other aspects of his illness (Parkinsonian features, bandemia) do not fit. His lung findings with hematuria might suggest a pulmonary/renal syndrome, but, once again, other features of his illness are not typical of these syndromes. Salmonella (typhoid fever) or influenza, now complicated by an early bacterial pneumonia, are viable possibilities.
The patient's ongoing clinical course is notable for a nontoxic (non‐SIRS) appearance but continued high‐grade fever with blood and urine cultures that are sterile. This argues against a common bacteremia with sepsis, and for either relapsing malaria (P vivax), influenza with a Parkinsonian‐like illness, typhoid fever, leptospirosis, dengue, or a rickettsial infection. Mycoplasma pneumonia is also possible given the atypical chest x‐ray appearance, slightly low hematocrit with elevated bilirubin, and neurological symptoms that may represent ataxia.
The subsequent negative laboratory tests listed are helpful in likely excluding many of the diagnoses suggested such as malaria, Babesia, common bacteremias, viral hepatitis, HIV, and WNV. Furthermore, the new history of mouse exposure brings to the forefront rodent‐associated infections, specifically exposure to mouse urine, a vehicle for leptospirosis. The patient's hepatitis, anemia, thrombocytopenia, scleral injection, along with the rest of his symptoms in the context of exposure to mouse urine makes leptospirosis the likely diagnosis. A negative Leptospira antibody early in his illness does not rule out the disease, and a convalescent titer should be obtained to confirm the diagnosis.
COMMENTARY
This case describes an elderly man who presented with a fever of unknown origin (FUO), and was eventually diagnosed with leptospirosis. FUO presents slightly differently in elderly patients, as elderly patients are less likely to mount a high fever, and when they do, the etiology is more likely to indicate a serious bacterial or viral infection. Additionally, an etiology for FUO in the elderly is found in over 70% of presenting cases, compared to 51% in patients under the age of 65 years.[1] A detailed, comprehensive social, travel, and exposure history and physical examination remains the cornerstone of elucidating the diagnosis for FUO. The exposure to mouse urine in this case was an unusual and a helpful piece of the history to further focus the differential diagnosis.
Leptospirosis is an emerging bacterial zoonosis, and causes both endemic and epidemic severe multisystem disease. The Leptospira spirochete is maintained in nature through a chronic renal infection in mammalian reservoir hosts, such as mice,[2, 4] and is transmitted through direct or aerosolized contact with infected urine or tissue. After a mean incubation period of 10 days, a variety of clinical manifestations may be seen. In this case, the patient's clinical presentation revealed many classic symptoms of leptospirosis, including fevers, rigors, headache, lower extremity myalgias, nausea, vomiting, and diarrhea; however, these symptoms are nonspecific. The presence of a conjunctival suffusion in leptospirosis infection had a specificity of 98% in a high‐incidence cohort of febrile patients in Sri Lanka,[3] and was an important diagnostic clue in this case. Leptospirosis is a self‐limited illness in most patients, with an initial septicemic, febrile phase followed by an immune phase. A more severe presentation may be seen in the immune phase of the illness, which includes renal and hepatic dysfunction (known as Weil's disease), as well as cardiac, pulmonary, and central nervous system abnormalities. With a 14% case fatality rate, the risk of death has been shown to be higher in patients over 40 years old, with altered mental status and multiorgan failure.[4]
The early diagnosis of leptospirosis relies heavily on physical exam findings and epidemiologic history. In this case, the patient's laboratory abnormalities, including immature granulocytes, thrombocytopenia, hyponatremia, hypokalemia, mild hepatitis, and pyuria with granular casts are all reported with leptospirosis infection2; however, independently, these laboratory findings are nonspecific. Patients may not have a detectable antibody levels in the acute phase of the disease. In this case, given the strong clinical suspicion based on the findings of conjunctival suffusion and exposure to mouse urine history, the lack of a more plausible alternate diagnosis, and known delay in antibody positivity, the patient was treated empirically with doxycycline for presumed leptospirosis.[5] Forthcoming novel diagnostic strategies such as next‐generation DNA sequencing techniques may provide real‐time diagnosis of this zoonotic infection, thus decreasing the window period between empirical antimicrobial coverage and diagnostic confirmation.[6]
Leptospirosis is prevalent in tropical climates and has been associated with impoverished communities.[7] Urban slums, with poor sanitation and high rodent density, are an ideal environment for leptospirosis. The reported risk of infection in a Brazilian slum was as high as 3% per year.[8] Additionally, rodent sightings, as well as the presence of chickens, were risk factors for leptospirosis transmission in urban slums.[9] Correspondingly in this case, we hypothesize that the patient's interest in urban farming, specifically the chickens he kept, likely attracted the mice infected with leptospirosis. Urban chicken farming is becoming increasingly popular in the United States,[10] and may be a developing risk factor for human leptospirosis infection. Leptospirosis is one of many emerging zoonoses, such as avian influenza, tick‐borne illness, and ebola, resulting from changing human ecology. Thus, when considering infectious etiologies, clinicians should ask patients about vocational and avocational exposures, including new trends such as urban farming, which may expose them to previously underappreciated illnesses.
TEACHING POINTS
- Elderly patients with a FUO are more likely to be diagnosed with an underlying serious bacterial or viral infection when compared to a younger cohort of FUO patients.
- The diagnosis of leptospirosis may initially be based on clinical suspicion in patients with classic features and exposures, noting the high specificity of conjunctival suffusion, and initial titers may be nondiagnostic; therefore, empiric treatment should be considered when clinical suspicion is high.
- Increased interest in urban chicken farming in the United States, with associated higher rodent density, may represent a newly recognized risk factor for human leptospirosis infection.
Disclosures
The authors report no conflicts of interest.
Fever in an elderly man is a nonspecific finding, occurring most commonly with infections but also with certain malignancies, rheumatologic disorders, and drug exposures. The complaint of rigors with diaphoresis makes an infection most likely. The acuity of his illness makes infections with more chronic presentations such as tuberculosis or actinomycosis less likely. The presence of frontal headache might suggest a sinus or brain source, but headache also occurs in generalized infections such as pneumonia, bacteremia from any cause, malaria, rickettsial infections, viral illnesses, and others. Additional history should include detailed inquiry into travel, vocational, and avocational exposures.
The patient's difficulty standing implies the development of lower extremity weakness and infections associated with neurological syndromes. His leg weakness may be related to early Guillain‐Barre syndrome, which is associated most commonly with Campylobacter jejuni, but also other bacteria and viruses such as Haemophilus influenza, Mycoplasma pneumonia, Influenza virus, Cytomegalovirus and hepatitis E. Other viral infections associated with pure motor deficits include echovirus, coxsackie virus, enterovirus, and West Nile virus (WNV). The paralytic syndrome associated with enteroviruses is more common in children, whereas the neuroinvasive variant of WNV more often affects the elderly and can be associated with encephalitis as well as a flaccid paralysis. Although acute paralytic shellfish poisoning could account for both his weakness and his acute gastrointestinal syndrome, this diagnosis is unlikely because the symptoms often have a prominent sensory component, and there is usually the history of recent ingestion of the suspect bivalves. Like all adults presenting for medical care, he should be screened for human immunodeficiency virus (HIV) infection; if testing is positive, the differential diagnosis for his current illness broadens significantly. Finally, he may have a spinal cord disorder or infection such as an epidural abscess, or transverse myelitis, which would present with lower extremity weakness and fever. It would be helpful to know the time of year of his illness, exposure to mosquito bites, his neurological exam findings, and results of blood and stool cultures. If the patient had signs of meningitis or encephalitis, cerebral spinal fluid analysis would be helpful. If his neurological exam was suggestive of cord involvement, it would be helpful to know the results of magnetic resonance imaging of the spinal cord.
The patient's past medical history includes relatively common problems for a 73‐year‐old man and does not substantially influence the differential diagnosis of his current illness. His travel history to Uganda a year previously may be relevant, because malaria (Plasmodium vivax) could present with fever and weakness. Less commonly, African trypanosomiasis (Trypanosoma brucei gambiense) can, in the late phase, present with fever and malaise, but also typically includes symptoms of encephalitis, including depressed mental status, confusion, ataxia, and possibly personality changes. His travel to Zurich should not impose any particular infection risk, unless he was hiking in the mountains around Zurich, where he could have contracted tick‐borne encephalitis; however, his travel more than 6 months prior to presentation makes this unlikely. Lyme disease due to Borrelia burgdorferi is also a potential exposure in the Swiss mountains, and can present with fever in the acute phase, as well as arthritis with chronic disease, but should not cause fever, rigor, diaphoresis, and headache many months later. Summering in Cape Cod puts him at risk for babesiosis, but an incubation period of 5 months is too long. Keeping chickens places him at risk for Salmonella exposure and typhoid fever. Ingesting raw oysters carries a risk for shellfish poisoning and Vibrio infections, but the incubation period (1 month) again seems too long to cause his current symptoms.
Notable physical findings are an ill‐appearing man with injected sclera and a high fever but normal blood pressure and heart rate. He also demonstrates proximal lower extremity weakness manifested by difficulty rising from a chair and a slow gait with short strides and deliberate (possibly on‐block) turning. His neurological exam is most consistent with Parkinsonian symptoms that have been described in patients with severe influenza A, which would explain all of his other symptoms as well. Pulse‐temperature dissociation is classically described with typhoid fever but usually occurs later in the disease course, and could be masked by the patient's metoprolol. Typhoid fever can also be associated with neurological symptoms including meningitis and movement disorders.
The patient has a remarkable bandemia, suggesting a bacterial infection, as well as a slight reduction in hematocrit and platelet count. Additionally, his labs revealed a mild transaminitis, but with significantly elevated alkaline phosphatase and GGT, and microscopic hematuria. His ferritin is significantly elevated, which may simply represent an acute phase reactant. Infections associated with hepatitis, cytopenias, and hematuria include sepsis with disseminated intravascular coagulation, previously mentioned malaria, leptospirosis, dengue, ehrlichiosis, and rickettsial diseases, but he has no special risks for these infections, and other aspects of his illness (Parkinsonian features, bandemia) do not fit. His lung findings with hematuria might suggest a pulmonary/renal syndrome, but, once again, other features of his illness are not typical of these syndromes. Salmonella (typhoid fever) or influenza, now complicated by an early bacterial pneumonia, are viable possibilities.
The patient's ongoing clinical course is notable for a nontoxic (non‐SIRS) appearance but continued high‐grade fever with blood and urine cultures that are sterile. This argues against a common bacteremia with sepsis, and for either relapsing malaria (P vivax), influenza with a Parkinsonian‐like illness, typhoid fever, leptospirosis, dengue, or a rickettsial infection. Mycoplasma pneumonia is also possible given the atypical chest x‐ray appearance, slightly low hematocrit with elevated bilirubin, and neurological symptoms that may represent ataxia.
The subsequent negative laboratory tests listed are helpful in likely excluding many of the diagnoses suggested such as malaria, Babesia, common bacteremias, viral hepatitis, HIV, and WNV. Furthermore, the new history of mouse exposure brings to the forefront rodent‐associated infections, specifically exposure to mouse urine, a vehicle for leptospirosis. The patient's hepatitis, anemia, thrombocytopenia, scleral injection, along with the rest of his symptoms in the context of exposure to mouse urine makes leptospirosis the likely diagnosis. A negative Leptospira antibody early in his illness does not rule out the disease, and a convalescent titer should be obtained to confirm the diagnosis.
COMMENTARY
This case describes an elderly man who presented with a fever of unknown origin (FUO), and was eventually diagnosed with leptospirosis. FUO presents slightly differently in elderly patients, as elderly patients are less likely to mount a high fever, and when they do, the etiology is more likely to indicate a serious bacterial or viral infection. Additionally, an etiology for FUO in the elderly is found in over 70% of presenting cases, compared to 51% in patients under the age of 65 years.[1] A detailed, comprehensive social, travel, and exposure history and physical examination remains the cornerstone of elucidating the diagnosis for FUO. The exposure to mouse urine in this case was an unusual and a helpful piece of the history to further focus the differential diagnosis.
Leptospirosis is an emerging bacterial zoonosis, and causes both endemic and epidemic severe multisystem disease. The Leptospira spirochete is maintained in nature through a chronic renal infection in mammalian reservoir hosts, such as mice,[2, 4] and is transmitted through direct or aerosolized contact with infected urine or tissue. After a mean incubation period of 10 days, a variety of clinical manifestations may be seen. In this case, the patient's clinical presentation revealed many classic symptoms of leptospirosis, including fevers, rigors, headache, lower extremity myalgias, nausea, vomiting, and diarrhea; however, these symptoms are nonspecific. The presence of a conjunctival suffusion in leptospirosis infection had a specificity of 98% in a high‐incidence cohort of febrile patients in Sri Lanka,[3] and was an important diagnostic clue in this case. Leptospirosis is a self‐limited illness in most patients, with an initial septicemic, febrile phase followed by an immune phase. A more severe presentation may be seen in the immune phase of the illness, which includes renal and hepatic dysfunction (known as Weil's disease), as well as cardiac, pulmonary, and central nervous system abnormalities. With a 14% case fatality rate, the risk of death has been shown to be higher in patients over 40 years old, with altered mental status and multiorgan failure.[4]
The early diagnosis of leptospirosis relies heavily on physical exam findings and epidemiologic history. In this case, the patient's laboratory abnormalities, including immature granulocytes, thrombocytopenia, hyponatremia, hypokalemia, mild hepatitis, and pyuria with granular casts are all reported with leptospirosis infection2; however, independently, these laboratory findings are nonspecific. Patients may not have a detectable antibody levels in the acute phase of the disease. In this case, given the strong clinical suspicion based on the findings of conjunctival suffusion and exposure to mouse urine history, the lack of a more plausible alternate diagnosis, and known delay in antibody positivity, the patient was treated empirically with doxycycline for presumed leptospirosis.[5] Forthcoming novel diagnostic strategies such as next‐generation DNA sequencing techniques may provide real‐time diagnosis of this zoonotic infection, thus decreasing the window period between empirical antimicrobial coverage and diagnostic confirmation.[6]
Leptospirosis is prevalent in tropical climates and has been associated with impoverished communities.[7] Urban slums, with poor sanitation and high rodent density, are an ideal environment for leptospirosis. The reported risk of infection in a Brazilian slum was as high as 3% per year.[8] Additionally, rodent sightings, as well as the presence of chickens, were risk factors for leptospirosis transmission in urban slums.[9] Correspondingly in this case, we hypothesize that the patient's interest in urban farming, specifically the chickens he kept, likely attracted the mice infected with leptospirosis. Urban chicken farming is becoming increasingly popular in the United States,[10] and may be a developing risk factor for human leptospirosis infection. Leptospirosis is one of many emerging zoonoses, such as avian influenza, tick‐borne illness, and ebola, resulting from changing human ecology. Thus, when considering infectious etiologies, clinicians should ask patients about vocational and avocational exposures, including new trends such as urban farming, which may expose them to previously underappreciated illnesses.
TEACHING POINTS
- Elderly patients with a FUO are more likely to be diagnosed with an underlying serious bacterial or viral infection when compared to a younger cohort of FUO patients.
- The diagnosis of leptospirosis may initially be based on clinical suspicion in patients with classic features and exposures, noting the high specificity of conjunctival suffusion, and initial titers may be nondiagnostic; therefore, empiric treatment should be considered when clinical suspicion is high.
- Increased interest in urban chicken farming in the United States, with associated higher rodent density, may represent a newly recognized risk factor for human leptospirosis infection.
Disclosures
The authors report no conflicts of interest.
- Fever of unknown origin in older persons. Infect Dis Clin North Am. 2007;21(4):937–945. , , .
- Leptospirosis. Clin Microbiol Rev. 2011;14(2):296–326. .
- Leptospirosis as frequent cause of acute febrile illness in southern Sri Lanka. Emerg Infect Dis. 2011;17(9):1678–1684. , , , et al.
- Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Philadelphia, PA: Elsevier; 2010. , , , et al.
- Antibiotics for leptospirosis. The Cochrane Database Syst Rev. 2012;2:CD008264. , .
- Actionable diagnosis of neuroleptospirosis by next‐generation sequencing. N Engl J Med. 2014;370(25):2408–2417. , , , et al.
- Cases distribution of leptospirosis in City of Manaus, State of Amazonas, Brazil, 2000–2010. Rev Soc Bras Med Trop. 2012;45(6):713–716. , , , .
- Prospective study of leptospirosis transmission in an urban slum community: role of poor environment in repeated exposures to the leptospira agent. PLoS Negl Trop Dis. 2014;8(5):e2927. , , , et al.
- Impact of environment and social gradient on leptospira infection in urban slums. PLoS Negl Trop Dis. 2008;2(4):e228. , , , et al.
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