Diminished cap formation in lymphocytes from patients and carriers of Duchenne muscular dystrophy.

Currently, the most useful clinical laboratory aid in establishing the carrier state of Duchenne muscular dystrophy is to determine creatine kinase (EC 2.7.3.2) activity in the plasma. The considerable overlap between plasma creatine kinase activities of controls and of carriers at the childbearing age contributes appreciable difficulty to genetic counseling of potential carriers. The consistent failure of lymphocyte cap formation in Duchenne muscular dystrophy patients and carriers in this study suggests a valuable tool for the confirmation of the carrier state.