Can Isotretinoin Induce Articular Symptoms in SAPHO Syndrome?

Abstract

The Editor, Sir, A 28-year old man visited his doctor because of hip pain (worse on the left side) and low back pain (worse with immobility/at night and better with activity) for the last 10 days. He stated that he had used oral isotretinoin for acneiform lesions for two weeks, and his complaints had ensued thereafter. He added that he had experienced a similar history with isotretinoin treatment when he was 20 years old as well. On physical examination, bilateral hip joint movements and lumbar flexion were painful. He also had limited range of motion in his left hip. Sacroiliac joints, sternum and sternoclavicular joints were painful with palpation. Gaenslen's and Mennel tests were positive, bilaterally. He had antalgic gait on the left side. He had severe nodulocystic acne with abcesses on his face, neck and back. C-reactive protein level was 1.87 mg/dL (N: 0–0.8 mg/dL). Laboratory tests including erythrocyte sedimentation rate, liver and kidney function tests and Brucella Rose Bengal test were all within normal limits. Radiographs were unremarkable. Magnetic resonance imaging (MRI) showed bilateral sacroiliitis (Fig. 1). Bone scintigraphy was consistent with bull's head sign (Fig. 2). Fig. 1 Magnetic resonance imaging demonstrating bilateral sacroiliitis (white arrowhead) on T1-weighted (A) and T-2 weighted (B) axial views. Fig. 2 Tc-99m bone scintigraphy showing increased uptake in manubrium sterni and bilateral costoclavicular joints (bull's head sign) and bilateral sacroiliac joints. Eventually, the patient was diagnosed with SAPHO (synovitis, acne, pustulosis, hyperostosis and osteitis) syndrome possibly induced by isotretinoin treatment. Isotretinoin was stopped and the patient was treated with indomethacin 75 mg/d. There was marked improvement in his complaints (except for acne) in the second month of follow-up. SAPHO syndrome is a chronic inflammatory disorder with findings of synovitis, acne, pustulosis, hyperostosis and sterile osteitis. To the best of our knowledge, isotretinoin was documented as a provoking factor for articular symptoms in SAPHO only in one case (1). Likewise, we herein present a case where SAPHO was precipitated with isotretinoin for acne treatment. SAPHO syndrome can be seen in all ages and it occurs with equal frequency in both genders. Although the exact aetiopathogenesis is yet unclear, it is supposed to be related to environmental, immunologic and genetic factors (2). The diagnosis of SAPHO is based on the exclusion of other causes (infectious discitis/osteomyelitis, malignancy, seronegative spondyloarthritis) with the presence of one of the following four items: (a) acne concomitant with bone involvement, (b) sternoclavicular hyperostosis, (c) palmoplantar pustulosis concomitant with bone involvement and (d) aseptic osteomyelitis (3). As for diagnostic imaging, radiographs are the initial tools to detect bone pathologies. Further, computed tomography and particularly MRI are more sensitive to show inflammatory changes (sacroiliitis, discitis, bone marrow oedema). The characteristic scintigraphy sign of ‘bull's head’ is typical for SAPHO (4). Concerning the laboratory investigations, SAPHO syndrome is usually accompanied by a moderate increase in erythrocyte sedimentation rate/C-reactive protein. Although nonspecific, there may be a mild increase in leukocyte and alkaline phosphatase levels (3, 4). Treatment for SAPHO is symptomatic ie non-steroidal anti-inflammatory drugs, corticosteroid, methotrexate, anti-tumour necrosis factor-alpha (TNF-α), pamidronate, or a combined drug approach (4, 5). In conclusion, we suggest that patients who are receiving isotretinoin treatment need to be followed for likely musculoskeletal complications and SAPHO syndrome must be kept in mind for the differential diagnosis.