Summary
Cutaneous mastocytoses are characterised by abnormal accumulation and proliferation of skin mastocytes. Most forms are isolated but cutaneous mastocytosis can occur in association with the systemic disease. The prevalence of mastocytosis in the general population is unknown. In England, the annual incidence is estimated at 1 in 150 000 individuals. Cutaneous mastocytoses are the most common form of mastocytosis but as these forms lead to milder clinical manifestations their prevalence also remains to be evaluated. Cutaneous forms represent between 0.1 and 0.8% of all dermatological consultations and are more common among the Caucasian population, with a higher frequency in males (at least for forms with childhood-onset). Cutaneous mastocytoses are associated with a polymorphic dermatological clinical picture, resulting from mastocyte infiltration. Four clinical forms have been described. Urticaria pigmentosa is the most frequent form (90% of cases). It affects children (1-8 per 1 000 births) between the ages of 2 and 5 years, and also adults. The disease manifests as small brown/red macules and papules, which vary in number from around 20 to several hundreds of lesions located mainly on the trunk and extremities. Darier's sign may be indicative for the diagnosis but it is not always present, particularly in adults. The papulonodular form of cutaneous mastocytosis occurs exclusively in infants and is sometimes present from birth. This form represents between 10 and 25% of all childhood cases of cutaneous mastocytosis. The lesions may swell becoming urticarial or even vesiculobullous if scratched or in response to certain foods or medication. Telangiectasia macularis eruptiva perstans is a rare form of cutaneous mastocytosis (1% of cases) occurring exclusively in adults and manifesting as brown/red telangiectatic erythematous lesions that are usually asymptomatic. Diffuse cutaneous mastocytosis is a very rare form affecting infants in the first 6 months of life. Generalised erythema and frequent, severe bullous eruptions may be present and can be followed by serious complications. Very rare cases have been reported in adults and in this case the cutaneous mastocytosis resembles an erythroderma with lichenoid features. Cutaneous mastocytoses are often associated with acute clinical features (lesion eruptions and flushes) resulting from mast cell degranulation and manifesting as sudden redness with diffuse pruritus, headaches, urticaria, nausea, vomiting, diarrhoea, dyspnea, bronchospasms, palpitations, hypotension or syncope. Other manifestations may also occur (mainly in adults): asthenia, depression, abdominal pain, and pollakiuria. Classically, the diagnosis of cutaneous mastocytosis is based on the histological examination. However, biopsy is not always required in child, or sometimes even in adult patients presenting with the characteristic clinical manifestations, particularly when Darier's sign is present as it is considered as pathognomic for the disease. At present, there is no curative treatment for cutaneous mastocytoses. Management revolves mainly around prevention of lesion eruption and flushes by avoiding triggering factors (certain foods and medication) and treatment of the other symptoms. Surgical excision or high dose local corticotherapy is sometimes recommended for children with cutaneous mastocytomas. The prognosis is generally good, particularly for children. However, persistent or adult-onset cutaneous mastocytosis may be associated with systemic forms of mastocytosis, diseases that may lead to severe or disabling manifestations. Patients should therefore be regularly evaluated for signs of systemic disease. *Author: Dr B. Flageul (October 2006)*.
