X‐linked bulbospinomuscular atrophy (Kennedy's disease) masquerading as lead neuropathy

Abstract

A 43-year-old male was referred by a veterinarian who evaluated his dog for a seizure and suspected a toxic lead exposure for both. He refurbished houses, removing old paint, and complained of decreased cognition, fatigue, and muscle cramps. He had a depressed affect, postural tremor, right arm weakness with partial denervation on EMG, and borderline-low sensory nerve action potential (SNAP) amplitudes. A mild anemia and elevated serum and urine lead levels supported a diagnosis of lead neuropathy. Chelation therapy increased urine lead excretion without symptomatic improvement. His brother worked part-time with him and developed similar findings, but also had difficulty chewing, dysphagia, perioral twitching, gynecomastia, and multifocal denervation of extremity and facial muscles. His lead levels were not elevated, but an androgen receptor mutation identified on the X chromosome for both brothers confirmed the diagnosis of X-linked bulbospinomuscular atrophy (Kennedy's disease).

Identification of Neurotoxic Disease

“…Most commonly, the diagnostic error is the consequence of an incomplete differential diagnosis combined with failure to verify the causes of the suspected disorder. Recognition of an uncommon neurologic disorder in the presence of documented exposure to a known neurotoxicant is particularly difficult (Albers and Bromberg, 1994).…”

Diagnosis and Management of Tremor

“…Tremor has been described in many neuropathies including X-linked bulbospinomuscular atrophy, 38 hereditary motor-sensory neuropathy, 39 multifocal motor neuropathy, 40 Charcot-Marie-Tooth syndrome, 41 Guillain-Barré syndrome, 42 and human Tlymphotropic virus 1-associated neuropathy, 43 but demyelinating neuropathies and dysgammaglobulinemic neuropathies are the most common causes of such tremors. 44,45 Characteristically, an action tremor resembling essential tremor is found in these patients.…”

Pseudoneurotoxic disease

“…5 He came to medical attention only after a veterinarian evaluated the painter's dog after a seizure, diagnosed the dog with lead poisoning, and recommended evaluation of the patient for lead toxicity, presumably because he had a potential source of lead exposure. Case 1: Example of Type 1 disease.…”