A 5 year old male child has multiple hyper pigmented macules over the trunk, on rubbing the lesion with the rounded end of a pen. He developed urticarial wheal, confined to the border of the lesion. The most likely diagnosis is (AIIMS Nov 2014)
|A||Fixed drug eruption|
Urticaria is characterized by large, irregularly shaped pruritic, erythematous wheels
1). Special forms of urticaria have special features (Dermographism, cholinergic urticaria, solar urticaria, or cold urticarial)
2). Most incidents are acute and self-limited over a period of 1-2 weeks
3). Chronic urticaria (episodes lasting> 6 weeks) may have an autoimmune basis
4). The most common immunologic mechanism is hypersensitivity mediated by IgE, seen for most patients with acute urticaria
5). The morphology of the lesions may vary over a period of minutes to hours, resulting in geographic or bizarre, pattern, true urticaria last less than 24 hours and often only 2-4 hours.
6. The most common cause of acute urticaria are foods, viral infections and medications Diagnosis - In vivo allergy skin testing and in vitro RAST testing
7. Most common cause of chronic urticaria- Idiopathic.
Urticaria pigmentosa (mastocytosis) - consists of multiple irregularly shaped hyperpigmented macule which may present on the trunk and extremities.
1). Stroking the skin through the lesion with a blunt instrument elicits the classical "triple response of Lewis" called Darier's sign
2). Treatment - Avoid taking drugs like Aspirin, NSAID', drugs, morphine, codeine, procaine, thiamine, polymyxin B and alcohol.
3). The main stay of treatment is initially includes HI antihistamines (Hydroxyzine, cyproheptadine, Loratadine)
4). Doxepin (TCA) - very effective in chronic urticaria.
5). Urticarial vasculitis may be seen as part of serum sickness, associated with fever and arthralgia.