DESTIN, FLA. – A simple mnemonic device can help to distinguish whether peripheral nervous system manifestations in patients with lupus and Sjögren’s syndrome are caused by the diseases themselves or by an alternate comorbidity, according to Dr. Julius Birnbaum.
The mnemonic device VITAMINS incorporates the spectrum of peripheral nervous system manifestations in lupus and Sjögren’s syndrome, and assists with the important task of fashioning a broad differential diagnosis and identifying the appropriate treatment, Dr. Birnbaum said at the Congress of Clinical Rheumatology.
Dr. Julius Birnbaum
Typically included in that spectrum of peripheral nervous system manifestations of lupus and Sjögren’s are a number of conditions that actually occur in less than 1% of patients, such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, plexopathy myasthenia gravis, and polyneuropathy without electrodiagnostic confirmation (except in cases of small-fiber neuropathy). Those conditions should therefore be considered as secondary and coincidental disease manifestations that can be managed as if the patient did not have lupus or Sjögren’s, said Dr. Birnbaum, associate professor of neurology at Johns Hopkins University, Baltimore.
Conversely, small-fiber neuropathies – painful sensory neuropathies that selectively or predominantly affect unmyelinated nociceptive fibers, are typically not included in that spectrum, but likely represent an underappreciated part of the spectrum of peripheral nervous system manifestations, he said. Small-fiber neuropathies are not detected by electrodiagnostic studies, which only test the integrity of larger-fiber myelinated nerves, he said.
In fact, in the context of supportive symptoms and physical examination, normal electromyography/nerve conduction velocity tests may actually support a diagnosis of small-fiber neuropathy. Furthermore, these neuropathies can cause unorthodox patterns of neuropathic pain, he said.
For example, in Sjögren’s syndrome, the patterns don’t always follow the typical “stocking and glove” distribution, and Sjögren’s patients with clinical features suggestive of small-fiber dysfunction may have normal skin biopsy studies.
Once these neuropathies are identified, the VITAMINS mnemonic can help in developing a differential. For small-fiber neuropathies, the mnemonic represents the following possible alternative causes:
V – Vascular diagnoses, namely systemic vasculitides, but this is probably uncommon, according to Dr. Birnbaum.
I – Infection, such as HIV and hepatitis C virus.
T – Trauma, although this is very rare.
A – Autoimmune/inflammatory disorders, especially celiac disease, sarcoidosis, and other rheumatic syndromes.
M – Metabolic disorders. This typically means diabetes, but impaired glucose tolerance can also be the culprit, so a 2-hour glucose tolerance test is important. Other possible metabolic causes of small-fiber neuropathy are vitamin B12 deficiency and hypothyroidism.
I – Inflammatory disorders, including amyloidosis, paraproteinemia, and cryoglobulinemia.
N – Neoplastic disorders, particularly paraneoplastic disorders.
S – Structural “mimics” such as syringomyelia and myeloradiculopathies.
Using this mnemonic, which “literally takes about 5 minutes,” is much easier than memorizing these numerous differential entities, he said.
A slightly altered version of the VITAMINS mnemonic can be used to identify the differential diagnoses for symmetric axonal polyneuropathies in lupus and Sjögren’s patients. In this case, the mnemonic represents the following alternative causes:
V – Vasculitis. “Sometimes a very rapidly coalescing vasculitis can give the facsimile of a polyneuropathy,” Dr. Birnbaum said.
I – Infection. As with small-fiber neuropathies, HIV and hepatitis C virus – even when not related to cryoglobulin – can cause symmetric axonal polyneuropathies.
T – Trauma, although this is very rare.
A – Autoimmune diseases, such as sarcoidosis.
M – Metabolic disorders, namely diabetes and impaired glucose tolerance. A 2-hour glucose tolerance test should be ordered.
I – Inflammatory disorders, including amyloidosis, paraproteinemia, and type 1 cryoglobulinemia.
N – Neoplastic disorders, particularly lymphomatous or other infiltrative neuropathies (although these are usually associated with asymmetric symptoms), chemotherapy, and/or paraneoplastic syndromes.
S – Structural causes. Compressive neuropathies are an example, although these are rare.
“Again you could use this mnemonic, and you’ll have the ability to really start honing in on pertinent and salient diagnoses, which might mimic a rheumatic disease,” Dr. Birnbaum said.
When it comes to treatment of these neuropathies and determining whether to use immunosuppressive therapies or symptomatic management, “it is useful to try to understand the relationship of a particular peripheral nervous system phenotype to disease activity versus disease damage,” he said.
Understanding differences in the characteristics of axonal neuropathy and mononeuritis multiplex can be helpful. For example, the prevalence of axonal polyneuropathies ranges from 1% to 10% in lupus and Sjögren’s, compared with a prevalence of less than 1% for mononeuritis multiplex. Also, lupus and Sjögren’s disease activity tends to be lower in the presence of axonal polyneuropathies and higher with mononeuritis multiplex.