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Nodular prurigo or Prurigo nodularis is a very itchy dermatosis of unknown etiology. It is characterized by: * Firm nodules, 1–3 cm in diameter, often with a verrucous surface. * Crusting and scaling may cover recently scratched lesions. * Older lesions may be darker or paler than surrounding skin. * Distribution is usually bilateral symmetrical. The lumps usually start on the forearms and legs, and are worse on the outer aspects. The trunk, face and even palms can also be affected. * Sometimes, the nodules
Etiology * The cause is unknown. It is uncertain whether scratching leads to the lumps, or if the lumps appear before they are scratched. * Up to 80% of patients have a personal or family history of atopic dermatitis, asthma or hay fever (compared to about 25% of the normal population). * PN may start as an insect bite reaction or another form of dermatitis. * PN has been associated with internal or cutaneous disease including: 1. Iron deficiency anemia 2. Chronic renal failure 3. Gluten enteropathy 4. HIV
Investigations 1. Skin biopsy: the diagnosis of PN is primarily clinical and may be confirmed by skin biopsy which shows enormously thickened skin that may appear quite abnormal, sometimes resembling squamous cell skin cancer. The nerve fibers and nerve endings in the skin are markedly increased in size. 2. Direct immunofluorescence is usually negative. 3. Other investigations are important to be arranged to identify underlying diseases that are associated with nodular prurigo such as: CBC, LFTs, RFTs and T