Abstract
Six patients with myotonic dystrophy in two families were reported.
FAMILY K. Two siblings, a 12-year-old boy and a 9-year-old girl, had histories of asphyxia and difficulty in sucking in the neonatal period, and showed a marked developmental delay. They were clumsy and slow in motion in their childhood. On examination, they rarely spoke and followed only simple directions. They walked awkwardly, and myotonia with muscular wasting was found. Cerebral atrophies on CT scans and cataracts were detected. These cases were considered congenital myotonic dystrophy.
Their mother, a 32-year-old woman, was healthy in her childhood and adolescence. She noticed easy fatigability and began to walk slowly after the first delivery. Muscular atrophy and myotonia were found on examination. She could speak fluently, but she was not cooperative. Cataract and cerebral atrophy were detected. Serum creatine phosphokinase (CPK) and IgG were normal in these cases.
FAMILY M. Two siblings, a 14-year-old boy and a 10-year-old girl, were born after uneventful deliveries, and began walking and speaking at 12 months of age. They were noted to be clumsy in their early childhood. They entered an elementary school, but made poor records at school. The brother complained of progressive difficulty in running. On examination, he was cooperative and muscular wasting with myotonia was found. Serum CPK was 615 IU/L (normal range: below 95 IU/L), and IgG was 528 mg/dl. The sister had consulted an ophthalmologist because of visual impairment, and cataract was detected. Her grip was 4-6 kg and percussion myotonia was found, but she had no complaint of daily life difficulty. Serum CPK was 220 IU/L and IgG was 517 mg/dl.
Their mother, a 37-year-old woman, noticed marked body weight loss and complained of difficulty in smooth movement of hands after the second delivery. On examination, muscular wasting and myotonia were found. She had normal intellect and no cataract. Serum CPK and IgG were 247 IU/L and 1243 mg/dl, respectively.
ELECTROPHYSIOLOGICAL STUDIES. On electromyography, myotonic discharges were disclosed in all cases. Most neuromuscular units were normal in amplitude and duration, and some polyphasic changes were found sporadically. The mean motor nerve conduction velocities in the ulnar and peroneal nerves were decreased significantly. The mean sensory nerve conduction velocity in the median nerve was decreased significantly in the distal part (from finger to wrist), but normal in the proximal part (from wrist to elbow).
These results indicated that peripheral nerve involvement, not only motor but also sensory nerves, occurred in myotonic dystrophy.
