Hereditary hypotonia, muscle weakness, failure to thrive, and cognitive delay in a large moslem kindred.

Five infants of a Moslem-Arab extended family were evaluated for common and characteristic clinical findings of failure to thrive, extreme muscle weakness, severe motor delay, and moderate to severe cognitive and verbal delay. All children were below the third percentile in weight and height, and three of them had head circumference below the third percentile. Neurologic examination revealed severe hypotonia, muscle weakness, and absent deep tendon reflexes. Two children died at 2 years of age, and none of the children acquired full head control and the motor milestones of rolling and sitting. Laboratory evaluation including muscle biopsies, genetic studies, and metabolic evaluation was nondiagnostic.