Abstract: Lipin-1 deficiency is a rare, life-threatening condition that causes severe rhabdomyolysis episodes (RM) triggered by febrile illness and effort. Now, the inventors treated 10 patients with LPIN1 mutations with hydroxychloroquine (HCQ) in an off open-label use phases 1 and 2 study, to assess safety, clinical, and biological effects of the drug. A first inclusion group of patients were treated with oral HCQ at a dose of 6.5 mg/Kg/day in one intake, not exceeding 400 mg/day. Five patients have not presented any new acute RM under treatment, except for 2 patients experimented one and two episodes of RM respectively despite HCQ in a context of gastroenteritis. Plasma levels of HCQ were in the range of 400 ng/ml except in the two patients who experimented RM, in whom the plasma HCQ levels were higher (1000 ng/ml). With a therapeutic adjustment, in order to maintain plasma levels of HCQ under 700 ng/ml, in a new group of patients, two patients did not suffer from new acute RM under treatment.