Systemic mastocytosis (SM) is a chronic myeloproliferative neoplasm characterized by the infiltration of atypical mast cells (MC). The major SM diagnostic criterion is the multifocal clustering of mast cells in the bone marrow. Minor SM criteria include an abnormal MC morphology and expression of CD25/CD2, an activating mutation at codon 816 of KIT, and a persistent serum tryptase concentration of > 20 ng/mL. When the major and at least 1 minor criterion or 3 minor criteria are fulfilled, the SM diagnosis is established. The World Health Organization (WHO) classification has recently recognized a subgroup of SM with an associated hematological neoplasm (SM-AHN), which is characterized by the presence of a concurrent neoplasm [1]. We present the case of a 72-year old woman suffering from SM associated with myelofibrosis (MF) referred to our center due to mild anemia and leukocytosis (Hb, 10.2 g/dL, WBC, 11,900/mm3, PLT, 368,000/mm3). The patient complained of fatigue, pruritus and weight loss. Physical examination revealed splenomegaly; Jak2V617F mutation and c-kit D816V mutation were detected. Basal tryptase value was 80.4 ng/mL.
Bone marrow flow cytometry showed aberrant CD2-CD25 expression in 5.5% of MC.
The bone marrow trephine biopsy showed:
A. Maturation defects of megakaryocytes with bulbous and naked nuclei (H&E, 20 ×); B. Diffuse and dense increase in reticulin fibers (MF2) (Argentic staining, 20 ×); C. Mastocytes are round to spindle-shaped cells, which have a clarified cytoplasm organized in aggregates of more than 15 elements (H&E, 40 ×); D. Marked CD117 cytoplasmic positivity in MC (40 ×).
We described the second case of association between SM and MF on the basis of the 2016 WHO classification. Xu and Xu previously reported a myeloproliferative neoplasm with splenomegaly in a 62-year-old woman. Biopsy results showed MF3 fibrosis and CD117 highlighted multifocal infiltrates of spindle-shaped/atypical MC in aggregates, consistent with the diagnosis of SM-AHN per 2016 WHO criteria [2].
Patients with SM often report unspecific symptoms secondary to histamine MC degranulation such as headache attacks, skin flushing, hypotensive crises, tachycardia, gastrointestinal complaints, osteopenia or osteoporosis. The most common triggers is an acute anaphylactoid reaction, caused by wasp or bee stings. Our patient was prescribed adrenaline fastject in case of anaphylactic reaction and started a treatment based on histamine H1- and H2-antagonist.
According to the International Prognostic Scoring System (IPSS) for MF (age > 60; WBC > 25,000/mm3; blast in blood > 1%; Hb < 10 g/dL and systemic B symptoms), the patient was considered intermediate-2 score, with a median survival time of 48 months (range 3–59). She was initially treated with low dose of hydroxyurea (500 mg/day) and it is planned to start with ruxolitinib [3].
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References
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