1. Symptoms are variable, and can include episodic attacks of itching, urticaria, dermographia, headache, flushing, syncope, palpitations, abdominal pain, diarrhoea, nausea, and vomiting.The flush is bright red and lasts for about 20 min, in contrast with that associated with carcinoid, which is more cyanotic and lasts for less than 10 min. Delay in diagnosis is frequent. In a series of 26 patients, the mean duration of symptoms before diagnosis was found to be 2 years (Webb et al 1982).
2. Attacks can be precipitated by alcohol, aspirin, NSAIDS, exposure to friction, pressure, temperature extremes, and insect stings.
3. Skin lesions vary in type and colour, but small, reddish brown maculopapular lesions are common.A positive Darier's sign may be demonstrated. Light stroking of the affected skin with a blunt, but pointed, object produces dermographia (secondary to localised urticaria), and a flare.
4. When bones are affected, the patient may present with unexpected bone loss, or compression fractures secondary to osteoporosis.
5. In a study of 41 patients, two-thirds had evidence of liver disease (Mican et al 1995). Hepatomegaly was detected in 24% and splenomegaly in 41%.
6. Increased gastric acid secretion is associated with duodenal ulceration. In one study, all patients with gastrointestinal symptoms were found to have increased plasma histamine levels, and these correlated with basal gastric acid output (Cherner et al 1985).
7. Skin biopsy shows an increased number of mast cells (>5 per high power field). Diagnosis may also be made on bone or liver biopsy.
8. Tryptase, a protease produced by all mast cells, is a clinical marker of systemic mastocytosis.Two types have been identified, a B12-measured and a G5-measured. Most patients with the systemic disease have B12 tryptase levels that are >20 ng ml-1, and are at least 10-fold greater than the corresponding G5-measured tryptase level, whereas most of those subjects with B12 tryptase <20ngml-1 had only cutaneous manifestations (Schwartz et al 1995). By contrast, in patients with systemic anaphylaxis without mastocytosis, the ratio ofB12- to G5-
measured tryptase was always <5 and approached unity (Schwartz et al 1994). Increased blood and urinary levels of histamine, and urinary prostaglandin D2 metabolite levels, may be demonstrated in systemic mastocytosis.
9. Certain groups of patients may develop haematological abnormalities, including malignancies.Anaemia, leucocytosis and thrombocytopenia were the commonest problems (Horny et al 1990), although thrombocythaemia has been reported (Le Tourneau et al 1991). Coagulation studies are occasionally abnormal.
10. Treatment is symptomatic only, and is aimed at blocking mast cell degranulation, or the effects of mast cell mediators on organs (Golkar & Bernhard 1997).
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