The clinical and EMG findings of lower motor neuron involvement suggested a diagnosis of spinal muscular atrophy. The spinal muscular atrophies of adult onset are a clinically well-defined group due to diverse genetic defects. Proximal muscles of the shoulders and pelvic girdles are affected earlier and to a greater extent then distal muscles. Intrinsic hand muscles are affected later in the course of the disease. Bulbar involvement is manifested initially as weakness and fasciculations of the oro-mandibular musculature, and subsequently by atrophy and fibrillations of the tongue.
Reflexes are usually absent.
Patients with these three distinct modes of inheritance present with a similar phenotype. Recent studies of the autosomal recessive forms of SMA have defined a single locus on chromosome 5q11.2-13.3 in acute infantile, late infantile, juvenile, and adult onset types. However it is still unclear how alterations in SMN give rise to the clinical syndrome of SMA, and what the role of NAIP is in this disease process. Our patient presented with evidence of both bulbar and spinal muscular atrophy as well as a mild degree of gynecomastia, but no testicular atrophy. The combination of symptoms and signs, including the prominent facial fasciculations, suggested the possible diagnosis of Kennedy's disease.