Systemic mastocytosis is an orphan myeloproliferative disease characterised by an excessive mast cell accumulation. Benign forms present with urticaria pigmentosa while aggressive subtypes or leukaemic variants lead to organ dysfunction. In patients with unexplained hypotensive syncope’s or anaphylaxis, flushing and angio-oedema with a basal tryptase >20 ng/mL, one should think of systemic mastocytosis. Pathophysiology is based on mutations in KIT, encoding the c-kit receptor (CD117) on the surface of mast cells. Diagnosis is based on bone marrow biopsies with clusters of atypical mast cells and co-expression of CD2 or CD25 and/or a KIT mutation. Treatment consists of avoiding triggers of mast cell release and antihistaminic drugs. Patients with aggressive subtypes are candidates for cytoreductive therapies. CD30 is thought to be a novel predictor of prognosis.

(BELG J HEMATOL 2013;4(3):85–89)