Introduction
Key features
Mastocytosis can develop from birth to adulthood and may involve only the skin (most children and some adults) or multiple organs such as the bone marrow, liver, spleen, and/or lymph nodes (primarily adults)
Childhood disease is more common and often presents with one or more tan to pink–brown or brown papules or plaques (maculopapular mastocytosis) that frequently resolve by adolescence
Mastocytomas are thicker plaques or nodules that are few in number and occur primarily in children
Adults with mastocytosis often have cutaneous lesions; when present, they typically appear as small red–brown macules or papules (“urticaria pigmentosa”) and tend to be associated with milder disease
Adult mastocytosis persists throughout life
Stroking of mastocytosis lesions often leads to urtication (Darier sign), which is more pronounced in children due to a higher density of mast cells
Activating mutations in codon 816 of KIT are detected in the majority of adults and ~40% of children with mastocytosis; extracellular domain mutations occur more often in childhood-onset than in adult-onset disease
Patients may have accompanying symptoms of mast cell mediator release such as pruritus, flushing, headaches, abdominal pain, diarrhea, and syncope
Treatment is primarily directed at controlling symptoms in patients with limited disease and inhibiting activating KIT mutations in those with more advanced disease