[A case of Kennedy-Alter-Sung (KAS) syndrome presenting as hypersexuality and elevated serum CK: usefulness of genetic analysis].

We report a unique case of KAS syndrome presenting as hypersexuality and elevated serum creatine kinase (CK). None of the other members of the patient's family had KAS. The patient had engaged in sexual behavior 4 approximately 5 times a week since his marriage. He did not have gynecomastia or hepatomegaly. Neurological examination revealed facial twitching and tongue atrophy and fasciculations. Mild to moderate muscular atrophy and weakness were evident in the proximal portion of the upper and the distal portion of the lower extremities. Deep tendon reflexes were absent, as were sensory disturbance and sphincter dysfunction. Laboratory data showed mild elevation of transaminase (GOT 113 U/L, GPT 69 U/L) and extreme elevation of CK (4,600 U/L) in serum. Electromyography and muscle biopsy from the left biceps showed chronic neurogenic atrophy. Genetic analysis showed increased expansion of a CAG repeat (44 repeats) in exon 1 of the androgen receptor gene. We diagnosed KAS syndrome based on the genetic analysis. This case is important in illustrating the clinical varieties of KAS syndrome, as well as the importance of genetic analysis in KAS syndrome cases presenting with atypical manifestations and without a family history.