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Mastocytosis at a Glance
  • The hallmark of mastocytosis is a pathologic accumulation of mast cells in tissues.
  • Mastocytosis occurs at any age.
  • The skin is the most commonly involved organ system.
  • Cutaneous findings consist of hyperpigmented macules, papules or nodules, or a diffuse infiltration of the dermis.
  • Generally benign in children.
  • In adults, most commonly associated with a somatic activating mutation of c-kit (codons 816 and 560).
  • Cutaneous manifestations may occur alone or in association with systemic disease.
  • Related features may be flushing, pruritus, hypotension, nausea, dyspepsia, and diarrhea.
  • Most common extracutaneous tissues involved are the bone marrow, liver, spleen, and lymph nodes.
  • May be associated with myeloproliferative and myelodysplastic disorders.
  • Classification of mastocytosis is critical for prognosis and treatment.
Mast Cells at a Glance
  • Mast cells are derived from pluripotent stem cells.
  • Stem cell factor is required for proliferation and survival.
  • Mast cells release both pre-formed and generated mediators when activated.

Mastocytosis represents a group of disorders characterized by an abnormal accumulation of mast cells in one or more organs. While the true incidence of this disease is unknown, most cases are in children, with 60%–80% presenting within the first year of life. Congenital mastocytosis is less common, representing approximately 18%–31% of childhood cases.1,2 Adult-onset mastocytosis also occurs and is being more commonly recognized with newly established World Health Organization (WHO) criteria for this disease3 (Tables 149-1 and 149-2). This disorder has no gender preference, and it has been reported in all races.4 While most patients with mastocytosis have no family history, there are reports of familial cases, including monozygotic twins, some of which were discordant for this disease.46

Table 149-1 World Health Organization Classification of Mastocytosisa
Table 149-2 Diagnostic Criteria for Systemic Mastocytosis (Major and One Minor or Three Minor Criteria Are Needed)a

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