Congenital myopathy-3 with rigid spine (CMYP3) is an autosomal recessive disorder of the skeletal muscle characterized by hypotonia and proximal muscle weakness apparent from birth or early childhood. Affected individuals show delayed motor development and develop progressive severe and deforming scoliosis ('rigid spine') in the first or second decades. Respiratory involvement due to diaphragmatic weakness is common, and most patients require ventilatory support due to nocturnal hypoventilation; recurrent respiratory infections are also observed. Additional features may include facial muscle weakness, amyotrophy, joint contractures, distal hyperlaxity, pulmonary hypertension with secondary cardiac dysfunction, and insulin resistance in those with a low BMI. The muscle weakness is not progressive, and most patients remain ambulatory. Skeletal muscle biopsy typically shows multiminicores, although there are often other abnormal nonspecific myopathic findings. This phenotype has been referred to as 'rigid spine syndrome' (Scoto et al., 2011; Fan et al., 2022; Varone et al., 2019).
For a discussion of genetic heterogeneity of congenital myopathy, see CMYP1A (117000). [from
OMIM]