[Myositis secondary to all-transretinoic acid during induction in acute promyelocytic leukemia]

Acute promyelocytic leukemia (APL) is a specific subtype of acute myeloid leukemia (AML) characterized by the presence of the 15;17 translocation, that generates the PML/RARalpha fusion gene. First-line induction treatment includes the combination of all-transretinoic acid (ATRA) and arsenic trioxide, with which complete response rates greater than 90% are achieved. Although the combination is very effective, there are adverse reactions associated with the treatment, which include cellular differentiation syndrome, headache, fatigue, elevated triglycerides, and myositis. The latter is rare and is manifested by intense muscle pain a few days after starting ATRA. Creatine phosphokinase (CPK) values are not always elevated and this can make diagnosis difficult with delayed treatment and increased risk of complications. We report the case of a woman with APL who, during the induction phase of treatment, presented myositis of the pelvic muscles and lower extremities secondary to the administration of ATRA. The condition resolved after the administration of corticosteroids and temporary suspension of ATRA, with no recurrence after its restart.