Cutaneous mastocytoma

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 79455

Definition

Cutaneous mastocytoma is a form of cutaneous mastocytosis (CM, see this term) generally characterized by the presence of a solitary or multiple hyperpigmented macules, plaques or nodules associated with abnormal accumulation of mast cells in the skin.

Epidemiology

Prevalence is unknown but mastocytomas are the second most frequent form of CM in children, accounting for 10-15% of cases.

Clinical description

Patients generally present during infancy, with most presenting in the first three months of life. However, rare cases of onset in adulthood have been reported. Mastocytomas usually appear as oval lesions with red-brown, pink or yellow pigmentation. The diameter varies from around 1-4 cm and the surface may be smooth or have a ''peau d'orange'' appearance. The trunk, face, neck and extremities are the most common sites of involvement. Patients with multiple mastocytomas (up to 5) have been reported with new lesions appearing at different locations up to two months after emergence of the initial lesion. Other skin manifestations may include blistering (most frequent during infancy), pruritus and urticaria. Stroking of the lesions results in Darier's sign and generalized flushing in some cases. Additional systemic symptoms are rarely associated with cutaneous mastocytomas but a few cases with fever, gastrointestinal disturbances (nausea, colic and diarrhea), headaches and asthma-like symptoms have been reported.

Etiology

Mutations in the KIT gene (4q11-q12) have been identified in some patients with CM, however, this mutation is rare in the pediatric population and the etiology and pathogenesis of cutaneous mastocytoma remains to be determined.

Diagnostic methods

Diagnosis is made on the basis of the clinical appearance of the lesions and the presence of Darier's sign. Histopathological examinations confirm the diagnosis by revealing a dense infiltrate of mast cells in the upper dermis.

Differential diagnosis

The differential diagnosis generally includes melanocytic nevi, xanthomas and juvenile xanthogranuloma (see this term).

Management and treatment

Treatment is symptomatic and includes oral administration of antihistamines, topical steroids and the use of hydrocolloid dressings to cover the lesions. Trigger factors (such as rubbing of the lesions and use of nonsteroidal anti- inflammatory drugs) should be avoided. Surgical excision provides a definitive cure for patients with alarming symptomatic lesions that do not respond to other forms of treatment and has been recommended as a first-line therapy in some cases.

Prognosis

The prognosis for patients with onset during infancy is good with regression of most lesions during childhood and complete resolution by adolescence. Rare cases of persisting mastocytoma in adulthood have been reported. Spontaneous resolution is less common in patients with adult-onset.

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