E075 Sacroiliitis potentially induced by isotretinoin: two case reports
Authors: Almansoori Hajar , Alnuaimi Noor , Alhosani Sara , Alshehhi Mahra , Al Nokhatha Shamma A 
Published: April 2024

Abstract

Background/Aims
Isotretinoin is a potent retinoid medication widely used to treat severe acne. Isotretinoin’s adverse effects range from well-documented dermatological side effects like dry skin to less common systemic manifestations. Sacroiliitis can arise from rheumatic and nonrheumatic causes. 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 case reports suggests a potential link in immunomodulation through the alteration of cytokine balance and degradation of synovial membranes in joints. We present two patients with severe acne history who developed bilateral sacroiliitis within several weeks after starting isotretinoin

Methods
Case 1: A 19 year old male, started on 20 mg daily isotretinoin for acne vulgaris, experienced severe hip and lower back pain after one month, impacting his mobility. On examination, he displayed painful hip movements. Lumbar flexion was restricted and painful, with a 2 cm measurement on the Schober’s test. 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 the sacroiliac joint was normal, but the MRI examination showed the presence of bilateral sacroiliitis. Case 2: A 34 year old female received a six-months isotretinoin treatment for severe acne, with doses ranging from 20-40 mg daily. Then, in 2018, after a six-year gap, she received another isotretinoin course at 30 mg daily. Four months later, she began to experience gradual, intermittent lower back pain associated with 30 minutes of early morning stiffness. Her vital signs were stable, but she exhibited restricted and painful lumbar flexion. Her investigations revealed normal ESR and CRP. HLA B27 was negative. Her sacroiliac joint X-ray showed normal results, but her MRI indicated bilateral active sacroiliitis.

Results
Following the discontinuation of isotretinoin in both cases, NSAIDs were administered, which effectively relieved the pain. 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
The two cases highlight the rare but noteworthy association between isotretinoin therapy and sacroiliitis. In patients presenting with unexplained musculoskeletal symptoms during isotretinoin treatment at any point, clinicians should raise suspicions on the adverse effects of medication. Further research is needed to elucidate the immunomodulatory pathways involved in this association.

Disclosure
H. Almansoori: None. N. Alnuaimi: None. S. Alhosani: None. M. Alshehhi: None. S.A. Al Nokhatha: None.