Doença de Kennedy: Relato de dois casos

X-linked spinal and bulbar muscular atrophy (Kennedy's disease) with long-term electrophysiological evaluation: case report

X-linked spinal and bulbar muscular atrophy or Kennedy's disease is an adult-onset motor neuronopathy caused by a CAG repeat expansion within the first exon of an androgen receptor gene. We report the case of a 66-year-old man, previously diagnosed with motor neuron disease (MND), who presented acute and reversible left vocal fold (dysphonia) and pharyngeal paresis, followed by a slowly progressive weakness and also bouts of weakness, wasting and fasciculation on tongue, masseter, face, pharyngeal, and some proximal more than distal upper limb muscles, associated to bilateral hand tremor and mild gynecomastia. There were 5 electroneuromyography exams between 1989 and 2003 that revealed chronic reinnervation, some fasciculations (less than clinically observed) and rare fibrillation potentials, and slowly progressive sensory nerve action potentials (SNAP) abnormality, leading to absent/low amplitude potentials. PCR techniques of DNA analysis showed an abnormal number of CAG repeats, found to be 44 (normal 11-34). Our case revealed an acute and asymmetric clinical presentation related to bulbar motoneurons; low amplitude/absent SNAP with mild asymmetry; a sub-clinical or subtle involvement of proximal/distal muscles of both upper and lower limbs; and a probable evolution with bouts of acute dennervation, followed by an efficient reinnervation.

[X-linked recessive bulbospinal muscular atrophy (Kennedy's disease). A family study]

Kennedy's disease is a rare type of motor neuron disease with a sex-linked recessive trait. DNA studies show a mutation at the androgen receptor gene on the long arm of X chromosome (Xq 11-12) with expanded CAG triplets (more than 347 repeats). We present three patients and one carrier among ten patients of a four generation family with clinical phenotype of the disease. The patients' ages ranged from 50 to 60 years with symptomatology usually beginning around 30 years of age. Patients had gynecomastia, testicular atrophy, muscular weakness, fasciculation, amyotrophy, absent deep tendon reflexes and postural tremor. PCR techniques of DNA analysis showed expanded size of CAG repeats on Xq 11-12 in all the three patients and in the carrier asymptomatic woman. This is the first Brazilian family with genetic molecular diagnosis of Kennedy's disease. This disease must be included in the differential diagnosis of motor neuron disease since it has a distinct prognosis and genetic counseling is mandatory to the carriers.