Myotonic dystrophy is more often symptomatic in infancy and early childhood than previously supposed, seven definite and two possible cases having come to our attention during a single year. In all but one case the disease was present, though unrecognized, in one or more members of preceding generations. At least three patterns of expression of the disease are suggested.

(1) The most common clinical syndrome (five cases) begins at birth or in early infancy with difficulty in nursing, attributable to bilateral facial weakness. Generalized myopathic weakness and hypotonia and variable degrees of retarded motor development are encountered during infancy. In one case there was no difficulty with bulbar musculature and only the limb muscles were involved. No evidence of a progressive loss of motor function has been observed during early childhood, but the pattern of greater proximal than distal weakness of extremities appears to become reversed gradually until the tyical adult distribution of weakness and atrophy is seen. The less common clinical syndromes, which include the two possible cases of myotonic dystrophy, are: (2) almost pure myotonia, symptomatic from early infancy (one case) or evident only on electromyography (one case) and (3) isolated congenital ptosis (one case).

Percussion myotonia or myotonia of grasp or both is usually present if looked for. Electromyographic evidence of myotonia has been found in every case and was of great help in establishing the diagnosis. Myopathic changes were identified in three of the five available muscle biopsies. Mental defect was an associated finding in onethird of the cases in the present series.

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