LAUSR

A primiparous pregnant woman in remission of myositis suffered very acute‐onset ritodrine‐induced rhabdomyolysis. At 29 gestational weeks, ritodrine was administered for threatened preterm labor. Just 3 h later, she complained of severe limb muscle pain, with serum creatinine phosphokinase elevated to 32 019 U/L and myoglobinuria. The muscle pain disappeared immediately after ceasing administration of ritodrine. At 31 weeks, premature rupture of the membranes occurred, necessitating cesarean section, yielding a baby with weak tonus, and the presence of infantile muscle diseases was suspected. Genetic analysis of the infant confirmed myotonic dystrophy (dystrophia myotonica, DM), which prompted us to perform maternal genetic analysis, confirming maternal DM. Ritodrine can induce rhabdomyolysis even in the prodromal phase with a mild phenotype of DM. A literature review suggested that ritodrine‐induced rhabdomyolysis may be likely to occur more acutely after ritodrine administration in DM compared with non‐DM mothers.