A detailed phenotypic description of 4 siblings (3 boys and 1 girl) with congenital muscular dystrophy and rigid spine syndrome is reported from the University of Utah, Salt Lake City, UT. They were offspring of a nonconsanguineous marraige and Northern European-American heritage. All 4 had hypotonia and neck weakness in infancy, early spinal rigidity, and early scoliosis, followed by skeletal deformities and respiratory insufficiency, the 3 oldest requiring noninvasive supportive ventilation. Muscle strength stabilized or slowly declined after initial improvement. Muscle biopsy at 9 months in one child revealed nonspecific myopathic changes, and his sibling at age 14 years had chronic and severe dystrophic changes, with normal dystrophin-glycoprotein staining. MRIs of the thigh muscles had shown selective muscle involvement early and widespread muscle abnormalities in later stages. Genetic studies showed linkage to the chromosome lp rigid spine locus (RSMD1) at 3 cM. 
COMMENT. Congenital muscular dystrophy/rigid spine syndrome is a distinct subtype of congenital muscular dystrophy with genetic heterogeneity. The syndrome linked to the RSMD1 locus is characterized by congenital hypotonia, stable or slowly progressive weakness, neck weakness, early spinal rigidity, early scoliosis, and respiratory insufficiency. MRI of thigh muscles before biopsy can be helpful in defining the location of selective involvement.
Dubowitz V discusses the development of the expanding syndrome of congenital muscular dystrophy , beginning with the classical paper of Frederick E Batten , followed by the equally classical pathological studies of Banker BQ et al , and the reports of syndromes by Fukuyama Y and others. Later, the merosin-deficient muscle biopsies and clinical characteristics of classical congenital muscular dystrophy were distinguished from the merosin-positive ones. One merosin-deficient syndrome of CMD combined with rigid spine syndrome in middle east consanguineous families is mapped to chromosome lp35-36.