La triptasi sierica nella diagnosi di mastocitosi sistemica in pazienti adulti senza lesioni cutanee

Background.: Mastocytosis is a rare disease characterized by clonal proliferation of mast cells in several organs, such as bone marrow, liver, spleen, skin, gastrointestinal tract and lymph nodes. The course of disease and the prognosis are variable. The typical skin lesion of mastocytosis is characterized by red to brown macules, known as urticaria pigmentosa (UP). However, in about 10–30% of patients, mastocytosis occurs in absence of typical skin lesions; in these patients, the clinical picture is mainly determined by mediator-related symptoms, such as urticaria, flushing, diarrhea and recurrent anaphylaxis. Thus, in patients without skin lesions, diagnosis of mastocytosis could be difficult. The determination of serum tryptase could be useful to improve diagnostic accuracy. Methods.: In our cohort of 67 patients (44 females and 23 males; mean age 28 years) with systemic mastocytosis (SM) we selected those without skin lesion and we evaluated their initial clinical features. The diagnosis of SM was made by bone marrow biopsy according the WHO criteria. Serum tryptase levels were determined using Phadia ImmunoCAP methodology and the analytical system Phadia 250 (Thermo Fisher Scientific, Waltham, MA, USA). Results.: Fifteen percent (10/67) of our patients with systemic mastocytosis have no skin lesions. Five of them are males (mean age: 55 years). The majority of patients (7/10) have ISM, one has a bone marrow mastocytosis (BMM), one has systemic mastocytosis associated to not clonal mast cells disorders (SM-AHNMD), and one has advanced systemic mastocytosis (ASM). The most frequent presenting symptom in these patients (4 out of 10) was pathological vertebral fracture due to severe osteoporosis. Other patients had severe anaphylaxis, progressive peripheral monocytosis and bone pain. In only one case the diagnosis was incidental, because bone marrow biopsy was done to confirm another diagnosis (essential thrombocythemia). In all cases, elevation of serum tryptase suggested the diagnosis of systemic mastocytosis. The values of tryptase in these patients ranged from 15 to 120 μg/L with a mean of 52 μg/L (normal range: up to 11.4 μg/L). Conclusions.: In patients without skin lesions, the diagnosis of mastocytosis could be challenging. The clinical presentations of mastocytosis are heterogeneous, ranging from severe clinical pictures of osteoporosis to hematologic abnormality in otherwise asymptomatic patients. Our data indicate that the diagnostic relevance of serum tryptase levels in patients without skin lesions, but with suspicious symptoms and/or signs of SM, and its utility in selecting patients who do need a bone marrow biopsy.