A 2 year old boy was referred to our clinic for evaluation of recurrent febrile episodes that have been occurring in the last year. The fevers occur every 3-4 weeks last several days and are accompanied by a prominent itchy rash that appears on the hands and feet with some lesions on the trunk. There is a mild relief by anti-histamine but the rash resolves after several days leaving a hyper pigmented lesion. His perinatal history was positive for hydronephrosis. His mother has severe vision impairment and his father has spinal stenosis. He is from North African descent. Laboratory work up reviled elevation of inflammatory markers on some occasions. Evaluation of period fevers with rash suggested several likely diagnoses including FMF and CAPS-Cryopyrin Associated Periodic Syndrome such as Muckle-Wells syndrome. Genetic tests for FMF were sent and genetics for CAPS were contemplated. Vasculitis was suggested since the rash resulted in hyper pigmented lesions. Therefore a Skin Biopsy during one of the episodes was performed, which showed Interface dermatitis and post inflammatory hyperpigmentation. After revision of history we were convinced that the rash only started after paracetamol use and pictures demonstrated that the rash occurred exactly at the same spots.
This suggested a possibility of Fixed Drug Eruption. We performed a provocative paracetamol challenge which demonstrated recurrence of the rash exactly on top of the hyper pigmented lesions. CAPS and fixed drug eruption which is often an elusive diagnosis will be discussed.
