Severe chronic diarrhea and maculopapular rash: a case report.

Systemic mastocytosis (SM) is a heterogeneous disease of the bone marrow characterized by abnormal growth, accumulation and activation of clonal mast cells (MCs). We report a case of SM with multi-organ involvement. A 30-year-old man presented with diarrhea, flushing, maculopapular rash with itching and weight loss. The upper and lower gastrointestinal endoscopies showed macroscopic involvement of stomach and duodenum; mucosal samples from stomach, duodenum, colon and distal ileum showed mucosal infiltration by large, spindle-shaped MCs with abnormal surface molecule expression (CD2 and CD25), a picture fully consistent with SM, according to the World Health Organization diagnostic criteria. A computed tomography scan showed diffuse lymphadenopathy, hepatosplenomegaly and diffuse small bowel involvement. Bone marrow aspirate and biopsy were diagnostic for SM; serum tryptase levels were increased (209 ng/mL, normal values < 20 ng/mL). The conclusive diagnosis was smouldering SM. There were no therapeutic indications except for treatment of symptoms. The patient was strictly followed up because of the risk of aggressive evolution.