0.101 Images of memorable cases: case 112

112. myotonic dystrophy

An autosomal dominant form of muscular dystrophy characterized by abnormally prolonged muscle contraction after active motion ormechanical stimulation. Typical associated features are frontal alopecia; lens opacities; atrophy of the temporalis, zygomaticus, and sternocleidomastoidmuscles; and gonadal atrophy in men. Widespread smooth muscle involvement may also cause cardiac conduction disturbances and arrhythmias, esophageal andcolonic dysfunction, and respiratory disability.

The patient shown had early frontal balding, wasting of his temporal and facial muscles, and virtually no visible neck orshoulder muscles. His inability to immediately relax his grip after the introductory handshake sealed the diagnosis.