Chondrodystrophic Myotonia: Report of Two Cases

Abstract

FAMILIAL myotonia is usually a manifestation of myotonia congenita, paramyotonia, myotonic dystrophy, or hyperkalemic periodic paralysis. These diseases affect the muscles, and, in patients with myotonic dystrophy, the lens, gonads, hair follicles, and, occasionally, the skeleton and central nervous system. Recently, familial myotonia and nonprogressive myopathy were described in association with a bone disease causing dwarfism, skeletal deformities, and anomalies of the face and orbital region.¹The skeletal deformities differed from those which occasionally occur in patients with myotonic dystrophy. Similar abnormalities have not been reported to occur as atypical manifestations of one of the known hereditary diseases associated with myotonia.²Because of the familial incidence, they are also very unlikely to result from the accidental association of two rare diseases, one affecting the muscles and the other the skeleton. These abnormalities probably are manifestations of a previously unrecognized hereditary disease. The results of the investigations of