Mondo Description An autosomal recessive condition caused by mutation(s) in the RYR1 gene, encoding ryanodine receptor 1. It may be characterized clinically by neonatal hypotonia, delayed motor development, and generalized muscle weakness, and amyotrophy. Pathologically, the absence of mitochondria and focal disorganization of the sarcomere appear as "minicores" on ATPase staining as a result of focal defects in oxidative activity.

Uniprot Description Clinically heterogeneous neuromuscular disorder. General features include neonatal hypotonia, delayed motor development, and generalized muscle weakness and amyotrophy, which may progress slowly or remain stable. Muscle biopsy shows multiple, poorly circumscribed, short areas of sarcomere disorganization and mitochondria depletion (areas termed minicores) in most muscle fibers. Typically, no dystrophic signs, such as muscle fiber necrosis or regeneration or significant endomysial fibrosis, are present in multiminicore disease.