Medical Q&As

Urticaria pigmentosa - what is it?

My three-year-old daughter has urticaria pigmentosa, which is a form of mastocytosis. What is the incidence of this skin condition in Ireland and is there a hospital that specializes in its treatment?

I have no information on the incidence of urticaria pigmentosa in Ireland but based on my twenty years of experience in general practice I would have thought that it is not very common. There is no special hospital centre that specialises in its treatment but any paediatric dermatologist would be well qualified to deal with it and advise on further management. The term urticaria pigmentosa literally means pigmented hives and it is manifest by the presence of brown patches on the skin due to an accumulation of mast cells in the skin. Mastocytosis refers to this accumulation of mast cells. Mast cells are widely distributed throughout the skin and they contain several chemicals including histamine. If the mast cell is disturbed it releases histamine into the surrounding skin giving rise to localised itching, redness and swelling. Rubbing and scratching the affected area of skin results in further histamine release with a further increase in discomfort. The condition usually arises in the early months of infancy and is often confused with insect bites. However the spots usually persist and can occur on any part of the body. A characteristic feature of the condition is that if one of the spots is rubbed the area becomes red, swollen and itchy. Sometimes this can progress on to blister formation. The condition tends to fade as the child progresses through childhood and by the time of adolescence the condition has usually disappeared. Exercise or heat can aggravate the condition, as can aspirin. Paradoxically low dose aspirin can be an effective treatment for some sufferers but the drug is probably best avoided unless the doctor has prescribed it. There is no specific blood test for the condition and it is usually diagnosed on the basis of its characteristic appearance. Oral antihistamines can be helpful in alleviating the condition. The term mast cell stabiliser refers to a class of drugs that inhibit the mast cells from releasing histamine too readily. These can also be very helpful to some sufferers. Some children need to be treated with potent steroid creams. The most severely affected children may need to be treated with interferon however such treatment rarely needs to be administered. Most children with the condition are mildly affected and only require occasional symptomatic relief.