RYR1 and periodic paralysis: RYR1 mutations may also give rise to episodic neuromuscular manifestations, including exertional myalgia and rhabdomyolysis,7 a late-onset axial myopathy,8,9 and have recently been associated with a novel bleeding disorder due to abnormal smooth muscle cell contractility.10 Episodes of atypical periodic paralysis (PP) have been previously reported in a single patient with a recessive RYR1-related myopathy,11 but it has been unclear whether this phenotype was unique to the reported individual or common across different RYR1 genotypes.