WHAT IS ACTINIC PRURIGO IN BRITAIN

Actinic prurigo (AP) belongs to the group of idiopathic photodermatose s sharing a predilection for occurring more commonly in females, and t here is much controversy as to whether it is only a more severe form o f polymorphous light eruption (PMLE) or whether it is a distinct entit y in its own right. The condition is characterised by intensely itchy papules, plaques and nodules, along with excoriations and scars usuall y starting before puberty, and predominantly involves the sun-exposed areas although it may also affect covered sites. Seasonal exacerbation s at the beginning of spring with improvement in the fall are typical, although the lesions frequently do not clear completely in the winter . The disorder may run a chronic course and persist into adulthood, bu t often spontaneous resolution occurs in late adolescence. Diagnosis i s predominantly based on the clinical features, cutaneous irradiation tests and histology often being normal or non-specific. HLA typing has also been performed in both PMLE and AP patients, showing a strong as sociation between HLA-DR4, in particular with the DRB10407 subtype, a nd AP; no HLA association has been found in PMLE. This HLA association is likely to be of pathogenic significance and strongly suggests a cr itical role for MHC-restricted antigen presentation in the development of photosensitivity AP.