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Author: Clin. Assoc. Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2009.
The term prurigo refers to intensely itchy spots. It may be used when the cause is known (see list below) or to describe a condition of unknown cause characterised by small itchy bumps.
Prurigo should be distinguished from pruritus (itch), in which there are no primary skin lesions.
Prurigo has primary and secondary skin lesions.
Prurigo simplex presents as symmetrically distributed, small, intensely itchy, dome-shaped bumps. Sometimes there are tiny blisters. They are most numerous on the outer aspects of the limbs and buttocks, but may occur anywhere on head and neck, trunk and limbs. Prurigo may affect children and adults.
Aternative names for prurigo simplex include chronic prurigo of adults, prurigo mitis, and Hebra prurigo. When the spots are dark in colour, it may be called prurigo pigmentosa.
Often the primary prurigo papule is no longer visible because scratching has removed it. Prurigo may cause considerable distress because severe itch can prevent sleep.
Nodular prurigo presents with hard warty nodules, often showing increased pigmentation. As they are very itchy, they are often ulcerated or crusted. Nodular prurigo is very resistant to treatment.
Prurigo pigmentosa is characterised by an itchy rash with a net-like pigmentation.
In some people, prurigo is associated with another skin condition or health problem. These include:
Treatment may include the following diverse agents.
More severe disease may be treated with immune suppressive agents.
Severe itch may be relieved by centrally acting medicines. These include:
As there are several skin conditions that present with prurigo, investigations may be necessary to make the diagnosis.
Skin biopsy is often performed to look for specific features of dermatitis herpetiformis, which are diagnostic of that condition. Direct immunofluorescence is also diagnostic for dermatitis herpetiformis. The histology of other forms of prurigo may be nonspecific, or show hyperkeratosis (scale), acanthosis (skin thickening) and inflammatory infiltrate (lymphocytes in the dermis).
Blood tests may include general health screening and indirect immunofluorescence tests.
Chest X-ray, CT scan or MRI may also be ordered. Further tests will depend on the results of initial screens.
Itchy prurigo papules may arise in several other skin disorders.
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