Monarch Disease Ontology identifier MONDO_0009712 (congenital multicore myopathy with external ophthalmoplegia) is 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. Also known as: minicore myopathy, antenatal onset, with arthrogryposis.