All of the following statements regarding mastocytosis are true EXCEPT:
ExplanationMastocytosis is a proliferation and accumulation of mast cells in one or more organ systems. Only the skin is involved in approximately 80% of cases, with the other 20% being defned as systemic mastocytosis due to the involvement of another organ system. The most common manifestation of mastocytosis is cutaneous urticaria pigmentosa, a maculopapular pigmented rash involving the papillary dermis. Other cutaneous forms include difuse cutaneous mastocytosis (almost entirely in children) and mastocytoma. Clinical manifestations of systemic mastocytosis are related to either cellular infltration of organs and/or release of histamine, proteases, eicosanoids, or heparin from mast cells. Therefore, signs and symptoms may include constitutional symptoms, skin manifestations (pruritus, dermatographia, rash), mediator-related symptoms (abdominal pain, fushing, syncope, hypertension, diarrhea), or bone-related symptoms (fracture, pain, arthralgia). In a recent series, 40% of patients with systemic mastocytosis had an associated myeloid neoplasm, most commonly myeloproliferative syndrome, CML, and MDS. Eosinophilia was present in approximately one-third of patients. Elevated serum tryptase, bone marrow involvement, splenomegaly, skeletal involvement, cytopenia, and malabsorption predict more aggressive disease and worse prognosis. Many patients with systemic mastocytosis have an activating mutation of c-KIT, a kinase inhibited by imatinib; however, the mutation appears relatively resistant to this agent.
