Nemaline myopathy has been associated with mutations in twelve genes to date. However, for some patients diagnosed with nemaline myopathy, definitive mutations are not identified in the known genes, suggesting there are other genes involved. This study describes compound heterozygosity for rare variants in RYR3 in one such patient. Clinical examination of the patient at 22 years of age revealed a long-narrow face, high arched palate and bilateral facial weakness. She had proximal weakness in all four limbs, mild scapular winging but no scoliosis. Muscle biopsy revealed wide variation in fibre size with type 1 fibre predominance and atrophy. Abundant nemaline bodies were located in perinuclear areas, subsarcolemmal and within the cytoplasm. No likely pathogenic mutations in known nemaline myopathy genes were identified. Copy number variation in known nemaline myopathy genes was excluded by nemaline myopathy targeted array-CGH. Next generation sequencing revealed compound heterozygous missense variants in the ryanodine receptor type 3 gene (RYR3). The results suggest that variants in RYR3 may cause a recessive muscle disease with pathological features including nemaline bodies.
