Pathophys:Abnormal mast cell proliferation, either neoplastic or reactive to soluble mast cell growth factor (Nejm 1993;328:1302), especially in skin and gi tract; intermittent chemical or mechanical irritation leads to release of histamine and prostaglandin D2, et al. (Ped Derm 1986;3:265)
Sx:Episodic attacks of flushing, itching, palpitations, headaches, orthostatic sx, hyperventilation, abdominal cramping; attacks may be precipitated by alcohol, narcotics, and aspirin; freckles all over body, if rubbed cause urticaria (urticaria pigmentosa) (J Invest Derm 1991;96:325)
Si:Orthostatic BP changes; brown macules and papules all over
Usually benign in children; may be severe in adults (J Intern Med 1996;239:157)
Lab:
Chem:serum tryptase levels elevated; 24-h urine especially after attack, for histamine metabolites (N-methylimidazole acetic acid, N-methylhistamine) and prostaglandin levels
Path:Skin bx shows 4+ mast cells in skin lesions
Rx:
Acutely, adrenalin
Chronically, prevent with:
- Avoidance of narcotics, alcohol, dextromethorphan cough medications, and aspirin
- Chlorpheniramine 8 mg po qid or other antihistamine (Med Let 1989;31:43)
- Cimetidine 300 mg qid po or other H2-blocker
- Na cromolyn 100 mg po (not inhalation) qid (Nejm 1979;301:465) for gi sx
- Ketotifen 2 mg po bid stabilizes mast cells (Ann IM 1986;104:507)
- PUVA rx (psoralens and UVA)
of mast cell tumor load: interferon-
2b causes dramatic regression (Nejm 1992;326:619)