Distinguishing clinical and electrodiagnostic features of x-linked bulbospinal neuronopathy

X-linked bulbospinal neuronopathy (XLBSN) or Kennedys disease is a rare inh erited neuromuscular disease characterized by adult-onset muscle weakness, usually in a limb-girdle distribution. It is frequently misdiagnosed despit e a distinctive clinical presentation, usually due to the absence of a clea r family history, and perhaps also due to failure of recognition. Accurate diagnosis is crucial for genetic counseling purposes and because alternativ e diagnoses usually carry a poorer prognosis. We evaluated 4 patients with XLBSN and one symptomatic female heterozygote patient. Based on our clinica l observations in these patients and a systematic review of previously repo rted cases, the following clinical and electrophysiologic features when pre sent in the setting of adult-onset muscle weakness, are strongly suggestive of the disorder: 1) facial weakness, 2) facial twitching or fasciculations , 3) tongue weakness and atrophy, 4) postural hand tremor, 5) hypo- or aref lexia, and 6) absent or low-amplitude sensory nerve action potentials despi te clinically normal sensation. We also hypothesize regarding the possibili ty of partial expression of the abnormal XLBSN gene in a symptomatic hetero zygote female patient. (C) 1999 John Wiley & Sons, Inc.