Mutations in genes including MTM1 (MIM 300415; myotubularin), DNM2 (MIM 602378; dynamin 2), BIN1 (MIM 601248; bridging integrator 1), RYR1 (MIM 180901; ryanodine receptor 1), CACNA1S (MIM 114208; alpha 1s subunit of the dihydropyridine receptor, DHPR), TTN (MIM 188840; titin), and SPEG (MIM 615950; striated preferentially expressed protein kinase) have been identified for over 60% of patients with CNM (4, 5). The gene discussed is SPEG; the disease is centronuclear myopathy.