¹Noor Yousif Alnuaimi, ¹Hajar Almansoori, ¹Sara Alhosani, ²Shamma Alnokatha

¹UAEU, ²Tawam Hospital

Introduction: We describe a rare case presented to our tertiary hospital with a clinical picture compatible with sacroiliitis potentially induced by isotretinoin in a young male.

Isotretinoin, a potent retinoid medication widely used in the treatment of severe acne. There are many side effects associated with isotretinoin use ranging from well-documented dermatological side effects like dry lips and cheilitis to less common systemic manifestations.

Sacroiliitis can arise from rheumatic and nonrheumatic causes such as spondyloarthropathies, osteoarthritis, pregnancy, and trauma. However, there has been limited attention in the literature to the rare occurrence of sacroiliitis as an adverse effect of isotretinoin. The precise mechanisms remain poorly understood, but the emergence of several case reports suggests a potential link in immunomodulation through the alteration of cytokine balance and degradation of synovial membranes in joints.

Method(s): A 19 year old male patient was started on a 20 mg daily isotretinoin therapy for his acne vulgaris, which appeared on the face and upper trunk. After one month, he began to suffer gradually from pain in his low back and hip which became severe impairing his mobility. Associated symptoms include alternating buttocks pain, nocturnal pain, and early morning stiffness lasting less than 30 minutes. He has no personal or family history of rheumatological diseases. On examination; his vital signs were stable and hip movements were painful, with limitations in internal and external rotation and a positive FABER test. Lumbar flexion was restricted and painful. Schober’s test was measured as 2 cm.

Medical investigation showed an elevation of Erythrocyte sedimentation rate (ESR): 66mm/h, and C-reactive protein (CRP): 81 mg/l. HLA B27 was negative. X-ray radiography of sacroiliac joint was normal (Figure 1a), but the MRI examination showed the presence of bilateral sacroiliitis (Figure 1b).

Following the exclusion of infectious etiologies and discontinuation of isotretinoin, along with the administration of NSAIDs, the pain in the lumbar and hip areas was alleviated. Subsequently, the inflammatory markers; ESR and CRP decreased to 12 mm/h and 9.6 mg/dl, respectively. He was lost to follow-up due to insurance-related problems and presented a year later unable to stand and walk for 3 days. His updated MRI revealed active on top of chronic bilateral sacroiliitis (Figure 1 c,d), accompanied by elevated inflammatory markers (ESR, 21 mm/h CRP, 17 mg/l). He was once again prescribed NSAIDs with a good response.

Result(s): Our management of isotretinoin-induced sacroiliitis follows guidelines adapted from the ASAS-EULAR algorithm for axial spondyloarthritis. The algorithm entails an initial treatment with NSAIDs if no contraindications and to be titrated up to the maximum effective dose before considering biological/ targeted synthetic disease-modifying antirheumatic drugs.

Conclusion(s): This case highlights the rare but noteworthy association between isotretinoin therapy and sacroiliitis. In patients presenting with unexplained musculoskeletal symptoms during isotretinoin treatment, clinicians should raise suspicions on the adverse effects of medication. Furthermore, this case report contributes to the growing body of knowledge regarding rare adverse effects of isotretinoin, in an attempt to allow further research to elucidate the immunomodulatory pathways involved