Mastocytosis is clonal and neoplastic proliferation of mast cells. Usually form ‘multifocal compact clusters’ or cohesive aggregates.Considered ‘rare’. Can happen at any age, but cutaneous forms more common in children. Disease range from dermatological lesions that regress, to life-threatening multi-or
Mast Cell Activation Syndrome : Symptoms compatible with mast cell activation, and significantly raised tryptase.MCAS is a significant clinical finding to document.If MCAS occur with KITD816V mutation, and SM criteria not met. This becomes monoclonal MCAS.
Assess 'B' (Burden) and 'C' (Cytoreduction) Findings (See green box)
B Findings>30% bone marrow involvement and tryptase >200ng/mLDysplasia or proliferation in other lineages, but does not meet definition of another myeloid neoplasm. And with relatively normal blood count. Hepatomegaly (without liver dysfunction), Splenomegaly (without hypersplenism), lymphadenopathyC FindingsMast cell infiltration related cytopenia (Hb < 100, PLT < 100, ANC < 1.0)Hepatomegaly with impaired liver function, portal hypertension, ascites. Osteolytic lesions (with or without fractures)Palpable splenomegaly with hypersplenismMalabsorption due to GI mast cell infiltrate.
Indolent (ISM)
Smouldering
Aggressive (ASM)
Destructive nature of mastocytosis is often due to the mediates (histamine, proteases etc) than actual mast cell infiltrate.Severe symptoms with elevated tryptase can be called Mast Cell activation syndrome. Although other causes of MCAS exist.
Mast Cell
Leukaemia (MCL)
Poor prognosis. <1 year survival usually.
Associated with
haematological neoplasm
(SM-AHN)
CMML most common, but can be MDS, MPN, MDS/MPN, AMLLymphoma and myeloma rare.KITD816V common, and can be detected in the non-mast cell neoplasm as well.
KIT D816V resistant to Imatinib and masatinibBut for KIT D816V negative patients imatinib can be usedMidostaurinPivotal Phase 2 TrialAvapritinibPhase 1 trialUncertain whether these medication actually change OS. Difficult to determine due to heterogeneity of patients with AHN. It is believed that OS is determined by AHN rather than ASM.