Institute of Bone and Joint Surgery

Pseudoporphyria (PP) is characterized by skin fragility, blistering and scarring in sun-exposed skin areas without abnormalities in porphyrin metabolism. The phenylpropionic acid derivative group of nonsteroidal anti-inflammatory drugs (NSAID), especially naproxen, is known to cause PP. Naproxen is currently one of the most prescribed drugs in the therapy of juvenile idiopathic arthritis (JIA). The prevalence of PP was determined in a 9-year retrospective study of children with JIA and associated diseases. In addition, we studied the incidence of PP in 196 patients (127 girls and 69 boys) with JIA and associated diseases treated with naproxen from July 2001 to March 2002, prospectively. We compared these data with a matched control group with JIA and associated diseases not treated with naproxen to identify risk factors for the development of PP. The incidence of PP in the group of children taking naproxen was 11.4%. PP was particularly frequent in children with the early onset pauciarticular subtype of JIA (EOPA-JIA) (mean age 4.5 years). PP was associated with signs of disease activity, as lower hemoglobin (< 11.75 g/dl), higher leukocyte counts (> 10,400/ul), and increased ESR (> 26mm/h). Co-medications, especially chloroquine intake, appeared to be additional risk factors. The median duration of naproxen therapy before onset of PP was 18.1 months and most children with PP developed their lesions within the first 2 years of naproxen treatment. JIA disease activity seems to be a confounding factor for PP. Especially EOPA-JIA patients with significant inflammation seem to be prone to develop PP under medication with naproxen.