Spinal and bulbar muscular atrophy (SBMA, or Kennedy's disease) is an X-linked, late-onset neuro-endocrine disorder characterized by degeneration of motor neurons in the spinal cord and brainstem and partial androgen insensitivity. We describe the case of a 59-year-old man who presented with diabetes mellitus, hypercholesterolemia, testicular atrophy, gynecomastia, and elevated serum creatine kinase (CK) levels. He did not have a familial history of motor neuron disease or neuromuscular symptoms or physical signs. Electromyographic (EMG) examination showed evidence of widespread denervation in muscles of different segmental innervation. Genetic studies found an abnormal 43 CAG repeat in the androgen receptor gene, leading to the diagnosis of SBMA. This report highlights the fact that SBMA can present with a pure endocrine phenotype and an absence of neuromuscular complaints or physical signs.
X-linked bulbar and spinal muscular atrophy (SBMA), or Kennedy's disease, is an adult-onset form of spinal amyotrophy characterized by X-linked recessive inheritance, involvement of bulbar and limb muscles, and frequent occurrence of endocrine disturbances such as gynecomastia, testicular atrophy, hypercholesterolemia (HC), and diabetes mellitus (DM). 1,2 Neurophysiological studies often demonstrate subclinical involvement of the sensory nerves in addition to denervation changes. 3 A mutation characterized by increased size of a polymorphic CAG repeat within the first exon of the androgen receptor (AR) gene has been identified as the putative cause of Kennedy's disease. 4 The CAG triplet is normally within the range of 17 to 26 repeats, whereas in patients with SBMA the number of CAG repeats was found to be in the range of 40 to 52 repeats with no overlap between normal individuals and affected patients. 4 Although the features of the disease are well known, the description of patients in whom a molecular diagnosis was made is rare and genotype-phenotype correlations are poorly understood.
We report the case of a patient with SBMA who presented with a pure endocrine form of the disease associating DM, HC, gynecomastia, testicular atrophy, and elevated serum creatine kinase (CK) levels without neuromuscular symptoms an without obvious neuromuscular physical signs.