We report the case of a 14-year-old boy with a completely normal medical and social background (good student and handball practice). A dentist monthly followed this patient for an orthodontic treatment. Facing with symptoms associating purpura, pancytopenia, and limbs pain, the first diagnosis that came to mind to emergency pediatricians was acute leukemia and the patient was addressed to a hematology department. However, additional psychiatry investigations revealed an avoiding restrictive food intake disorder (ARFID) associated with serious vitamin deficiencies (Vitamins B9 and D) and responsible for scurvy, mimicking acute leukemia onset. Strikingly, this young patient has been undergoing a close medical follow-up since infancy because of a selective diet. Since growth, education, and development were normal, the risk of pursuing this unbalanced diet has been neglected and this child was admitted at diagnosis in a life-threatening condition.