Systemic mastocytosis is a rare heterogeneous disorder characterised by abnormal proliferation of mast cells. It can be divided in subtypes with different phenotypes and prognoses. This article is a retrospective descriptive study of 37 patients with systemic mastocytosis according to the WHO criteria of 2008 at UZ Leuven. Twenty-eight patients had indolent systemic mastocytosis (75.7%), four smouldering systemic mastocytosis (10.8%), three aggressive systemic mastocytosis (8.1%) and two systemic mastocytosis with associated haematological neoplasia (5.4%). In one out of five patients, the diagnosis was made based on at least three minor criteria. The sensitivity of CD25 expression was 100%. In 75.7% a KITD816V mutation was detected. The value of serum tryptase was associated with the subtype of systemic mastocytosis. Seventy-eight percent had cutaneous lesions. Forty-eight percent experienced at least one anaphylactic reaction. Osteoporosis was reported in 24.6%. Eighty-nine percent and 64.9% of patients were treated with respectively H1 and H2 antihistamines. Cytoreductive treatment was administered to nine patients (24.3%). Three patients received as first-line treatment midostaurine, three imatinib, one cladribine, one nilotinib and one masitinib. This study reflects the heterogeneity of this condition and emphasises the importance of a multidisciplinary approach in a specialised center for early diagnosis and treatment of disease-associated manifestations.

(BELG J HEMATOL 2019;10(7):265–76)