CONGENITAL MYOTONIC-DYSTROPHY PATHOLOGY AND SOMATIC MOSAICISM

We present the pathology and molecular genetic analysis of an infant w ith congenital myotonic dystrophy. The proband/infant, born at 35 week s' gestational age to a mother with myotonic dystrophy and 750 CTG rep eats, was markedly hypotonic and had severe cardiomyopathy. She died a fter 16 days of life. At autopsy, skeletal and heart muscles were imma ture and had a decrease in contractile elements. DNA CTG trinucleotide repeat analysis of the proband demonstrated 2,480 repeats in blood an d a slightly greater number of repeats in skeletal muscles, viscera, a nd gray matter. Corresponding to the clinical course and pathology, ca rdiac tissues displayed somatic mosaicism, with repeats ranging from 2 ,760 to 3,220.