Where modern medicine was born and still lives.
This page was last updated in March 2013.
This child skin showed multiple, generalized tan to brown macules/papules with classic features. Pigmentation and all evidence of the disease commonly disappear within a few years, generally before puberty. The eruption, however, may uncommonly persist into adult life. Although systemic involvement is possible, malignant systemic disease is extremely rare.
Such lesions are often confused with insect bites at first, but they persist and gradually increase in number for several months or years. Many children and adults have few, if any, symptoms. Childhood urticaria pigmentosa usually develops in the first year of life. Adult urticaria pigmentosa usually develops between 20 and 40 years. The lesions appear anywhere on the body but classically sparing the central face, scalp, palms and soles. Stroking a lesion with the blunt end of a pen induces a weal of the entire lesion that is usually confined to the stroked site (Darier's sign). The weal may take up to 10 minutes to appear. Stroking may also produce wealing in clinically unaffected skin. Darier’s sign is more pronounced in children due to a higher density of mast cells and the rubbed area may even blister. This test is highly characteristic and is usually seen as reliable as a biopsy for establishing the diagnosis. Having said so, Darier’s sign is not always demonstrable and is not 100% specific for mastocytosis, since it has also been described rarely in juvenile xanthogranuloma and acute lymphoblastic leukaemia of neonates. Interestingly, juvenile xanthogranuloma has been reported in association with urticaria pigmentosa*.
A skin biopsy is desirable to confirm a clinical diagnosis in many patients, although observation alone is appropriate in very young children. A full blood count should be performed at presentation and at yearly intervals when systemic disease is suspected. Other investigations should be guided by the clinical presentation. Juvenile xanthogranuloma is generally a self-healing tumour and lesions generally resolve in 1–5 years. Having said so, disseminated neonatal juvenile xanthogranuloma may be more aggressive and fatalities in this group have been reported. The major difficulty in clinical diagnosis of juvenile xanthogranuloma is with the nodular forms of Langerhans’ cell histiocytosis. Histopathology and immunocytochemistry will easily differentiate the two disorders. Some believe that benign cephalic histiocytosis represents a clinical variant of juvenile xanthogranuloma but the clinical features of the disease are distinct enough to maintain a separate nomenclature.
*DeVillez RL, Limmer BL. Juvenile xanthogranuloma and urticaria pigmentosa. Arch Dermatol 1975; 111: 365–6.
This page was last updated in November 2015.