Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome in a 14-year-old boy: an immunohistochemical study of infiltrating lymphocytes in acneous skin regions.

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome was proposed as a clinico-radiological entity combining skin, bone and joint manifestations [1]. Here, we report a 14-year-old boy with SAPHO syndrome, in whom we investigated the pathology of acneous skin regions with aberrant T-cell lymphocyte infiltration in the dermal area. A 14-year-old boy was admitted to our hospital exhibiting persistent high-grade fever with acne conglobata, in addition to chest, left knee joint and lumbar pain. Physical examination revealed swelling of the left knee joint and severe facial acne (Fig. 1). Haematological and biochemical investigations were all normal; however, C-reactive protein was 8.58 mg/dl and the ESR was 54 mm/h. Urinalysis showed normal findings. The purified protein derivative of tuberculosis reaction was unchanged from the previous year. Blood, urine, stool and pharyngeal cultures were all negative. Compliment, ferritin, and serum immunoglobulin level were normal. LE test, antibodies related to collagen diseases and tumour markers were all negative. Gallium scintigraphy showed abnormal accumulation in the left iliosacral joint, bilateral parotid glands, and acne lesions of the forehead (Fig. 2). CT scans of the pelvis showed increased space in the left iliosacral joint, thus suggesting swelling of the joint cartilage, but no solid-type periosteal reaction [6] were observed (Fig. 3). After admission, we treated the patient with intravenous antibiotics, but the clinical symptoms remained unchanged. For differential diagnosis, we performed a skin biopsy and found pyoderma with focal foreign body reaction and aberrant lymphoid cell infiltration (Fig. 4). We then started to administer oral ibuprofen. Clinical symptoms and laboratory findings improved rapidly after ibuprofen administration. Two years after discharge, his course has been uneventful with continued oral administration of ibuprofen. Because our case has not been refractory, we did not use pamidronate [4].