Our patient ultimately was diagnosed with primary cutaneous nocardiosis resulting from a traumatic injury to the skin that was contaminated with soil. The clinical manifestation pattern was a compound type, including both mycetoma and sporotrichoid infections. Initially, Nocardia mycetoma occurred with subcutaneous infection by direct extension10,11 and appeared as dense, predominantly painless, swollen lesions. After 4 years, the skin lesions continued to spread linearly to the patient’s upper arm and forearm and manifested as the sporotrichoid infection type with painful swollen lesions at the site of inoculation and painful enlargement of the ipsilateral axillary lymph node.
Although nocardiosis is found worldwide, it is endemic to tropical and subtropical regions such as India, Africa, Southeast Asia, and Latin America.12 Nocardiosis most often is observed in individuals aged 20 to 40 years. It affects men more than women, and it commonly occurs in field laborers and cultivators whose occupations involve direct contact with the soil.13 Most lesions are found on the lower extremities, though localized nocardiosis infections can occur in other areas such as the neck, breasts, back, buttocks, and elbows.
Our patient initially was misdiagnosed, and treatment was delayed for several reasons. First, nocardiosis is not common in China, and most clinicians are unfamiliar with the disease. Second, the related lesions do not have specific features, and our patient had a complex clinical presentation that included mycetoma and sporotrichoid infection. Third, the characteristic grain of Nocardia species is small but that of N brasiliensis is even smaller (approximately 0.1–0.2 mm in diameter), which makes visualization difficult in both histopathologic and microbiologic examinations.14 The histopathologic examination results of our patient in the local hospital were nonspecific. Fourth, our patient did not initially go to the hospital but instead purchased some over-the-counter antibiotic ointments for external application because the lesions were painless. Moreover, microbiologic smear and culture examinations were not conducted in the local hospital before administering antituberculosis treatment to the patient. Instead, a polymerase chain reaction examination of skin lesion tissue for tubercle bacilli and atypical mycobacteria was negative. These findings imply that the traditional microbial smear and culture evaluations cannot be omitted. Furthermore, culture examinations should be conducted on multiple skin tissue and purulent fluid specimens to increase the likelihood of detection. These cultures should be monitored for at least 2 to 4 weeks because Nocardia is a slow-growing organism.10
The optimal antimicrobial treatment regimens for nocardiosis have not been firmly established.15 Trimethoprim-sulfamethoxazole is regarded as the first-line antimicrobial agent for treatment of nocardial infections. The optimal duration of antimicrobial therapy for nocardiosis also has not been determined, and the treatment regimen depends on the severity and extent of the infection as well as on the presence of infection-related complications. The main complication is bone involvement. Notable bony changes include periosteal thickening, osteoporosis, and osteolysis.
We considered the severity of skin lesions and bone marrow invasion in our patient and planned to treat him continually with oral trimethoprim-sulfamethoxazole according to the in vitro drug susceptibility test. The patient showed clinical improvement after 1 month of treatment, and he continued to improve after 6 months of treatment. To prevent recurrence, we found it necessary to treat the patient with a long-term antibiotic course over 6 to 12 months.16
Cutaneous nocardiosis remains a diagnostic challenge because of its nonspecific and diverse clinical and histopathological presentations. Diagnosis is further complicated by the inherent difficulty of cultivating and identifying the clinical isolate in the laboratory. A high degree of clinical suspicion followed by successful identification of the organism by a laboratory technologist will aid in the early diagnosis and treatment of the infection, ultimately reducing the risk for complications and morbidity.