Images of Memorable Cases: Case 112 This 40-year-old man presented with bilateral cataracts and complete heart block. 112. Myotonic dystrophy An autosomal dominant form of muscular dystrophy characterized by abnormally prolonged muscle contraction after active motion or mechanical stimulation. Typical associated features are frontal alopecia; lens opacities; atrophy of the temporalis, zygomaticus, and sternocleidomastoid muscles; and gonadal atrophy in men. Widespread smooth muscle involvement may also cause cardiac conduction disturbances and arrhythmias, esophageal and colonic dysfunction, and respiratory disability. The patient shown had early frontal balding, wasting of his temporal and facial muscles, and virtually no visible neck or shoulder muscles. His inability to immediately relax his grip after the introductory handshake sealed the diagnosis.