[A case of deletion of the short arm of chromosome 18 associated with chronic polymyositis].

A case of deletion of the short arm of chromosome 18 (18p- syndrome) associated with chronic polymyositis is described. The patient was a 37-year-old woman, who had psychomotor retardation in her early childhood. She started to notice a difficulty in raising both arms at 14 years of age and furthermore, she developed a gait disturbance due to weakness of the proximal muscles of the lower extremities from 34 years of age. Her parents were first cousins. On physical examination, she showed many dysmorphic features, such as short stature, round face, hypertelorism, low nasal bridge, small chin, high arched palate, abnormal dentition, short and webbed neck, and broad chest. Neurological examination revealed a low intelligence (IQ 47), severe proximal muscle weakness with moderate proximal muscle atrophy in all extremities, a waddling gait, and decreased or absent deep tendon reflexes of all extremities except for bilateral ankle jerks. Serum creatine kinase and myoglobin levels were slightly elevated. Needle EMG study showed fibrillation potentials at rest and polyphasic and low amplitude motor unit potentials of short duration on volitional activity in the affected muscles. Muscle biopsy demonstrated a variation in fiber size, necrotic fibers and mononuclear cell infiltration. These findings were compatible with those of chronic polymyositis. In addition, cytogenetic findings revealed 46.XX.18p- karyotype, although her parents had no chromosome abnormality. She had no immunological abnormality except for a positive rheumatoid factor and elevation of CD4/CD8 ratio on lymphocyte subset analysis in peripheral blood.(ABSTRACT TRUNCATED AT 250 WORDS)