Pruritic eruption in a young woman with fever

A 29-year-old woman presented with 3 weeks of fever, arthralgia and pruritic rashes on her trunk and limbs. She had no significant medical history and denied occurrence of muscle weakness, dysphagia, mouth ulcers, alopecia and sicca symptoms. Physical examination revealed erythematous, oedematous papules and plaques on the anterior sternum, upper to mid-back, arms, flanks and lateral aspect of the proximal thighs. Antinuclear antibody and anti-double-stranded DNA were negative. Complements, creatine kinase and myositis panel were normal. Her erythrocyte sediment rate and ferritin levels were elevated at 48 mm h^-1 and 580 µg L^-1, respectively. Histological examination of the plaque on her upper back revealed epidermal dyskeratosis, with a mixed perivascular infiltrate of neutrophils, lymphocytes and histiocytes within the superficial dermis. There was prominent nuclear dust, red cell extravasation and increased dermal mucin. Direct immunofluorescence was negative. She was eventually diagnosed with persistent pruritic eruption (PPE) of adult-onset Still disease (AOSD) and was treated with oral etoricoxib with resolution of her fever and symptoms. The entity of PPE in AOSD is associated with the striking histological feature of dyskeratotic keratinocytes in the upper one-third of the epidermis. This is in contrast to other conditions such as cutaneous lupus or dermatomyositis, where the dyskeratotic keratinocytes are found in the lower epidermis instead. This case highlights the importance of clinicopathological correlation and recognition of PPEs in AOSD in view of the associated poorer prognosis due to associated conditions such as secondary macrophage activation syndrome.