MedGen

Congenital myopathy-9A (CMYO9A) is an autosomal recessive early-onset severe muscular disorder resulting in early death. Affected individuals present at birth with neonatal hypotonia, poor feeding, fractures of the long bones, and respiratory insufficiency. Laboratory investigations are consistent with a defect in early muscle development (summary by Estan et al., 2019). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000). [from OMIM]

Congenital myopathy-9B (CMYO9B) is an autosomal recessive early-onset skeletal muscle disorder mainly affecting proximal muscles. Affected individuals have neonatal hypotonia followed by mildly delayed walking in childhood. Muscle weakness is slowly progressive, resulting in positive Gowers sign and difficulty running or climbing, but most patients remain ambulatory. Some patients develop respiratory involvement requiring ventilatory support, whereas cardiac function is unaffected. Muscle biopsy shows type 1 fiber predominance with disorganized Z-lines and multiminicore myopathy (Estan et al., 2019). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000). [from OMIM]