PAPA syndrome is caused by mutations in a gene on chromosome 15q. The mutated gene produces a hyperphosphorylated protein that binds excessively to pyrin, thus restricting pyrin’s anti-inflammatory activity.
Arthritis begins in the first decade of life and is progressively destructive. Episodes of mild trauma may trigger the arthritis. Poorly healing ulcers with undermined edges may appear, often at sites of injury (eg, at vaccination sites). Acne is usually nodulocystic and, if untreated, causes scarring.
Diagnosis of PAPA is based on clinical findings and a family history. The ulcers may be biopsied. Biopsy shows superficial ulceration and neutrophilic inflammation.
Treatment with etanercept or anakinra may be useful. Acne is treated with oral tetracycline or isotretinoin.