nodular prurigo is characterized clinically by intensely itchy nodules which may be associated with an eczematous eruption. Patients are frequently tormented by their symptoms which often prove difficult to control with conventional therapy (1)
Clinical features:
occurs mainly in adults aged 20-60 years
affects both sexes equally
individual prurigo nodule is a firm lump, 1-3 cm in diameter - lesions often have a raised warty surface
early lesion may start as a smaller red itchy bump
crusting and scaling may cover recently scratched lesions
older lesions may be darker or paler than surrounding skin
there is often dry skin between the nodules
the lesions are intensely itchy - they are frequently excoriated and sometimes secondarily infected
lesions generally start on the lower arms and legs, and are worse on the outer aspects; other sites that may be affected include the trunk, face and palms
Aetiology:
cause of nodular prurigo is unknown
atopy is found in 65–80% of patients in whom the disease may occur at an earlier age (1)
nodular prurigo has been associated with internal disease including iron deficiency anaemia, chronic renal failure, gluten enteropathy, HIV infection
Investigations
occasionally skin biopsy is useful to confirm the diagnosis
histology may resemble lichen simplex but with greater hyperkeratosis
dense dermal infiltrate and vascular hyperplasia - these changes are likely to represent a non-specific reaction to scratching
direct immunofluorescence is usually negative
screening for associated diseases
blood tests may include full blood count, liver, kidney and thyroid function tests
Reference:
Woo PN et al. Br J Dermatol. 2000 Jul;143(1):215-6.
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