Isotretinoin, a vitamin A derivative, is approved by the Food and Drug Administration as a cure for severe recalcitrant acne vulgaris, and recommended for severe nodular acne and treatment resistant moderate acne. 1 Many adverse effects associated with the isotretinoin use have been reported. Among those, the most common adverse effects include mucocutaneous, musculoskeletal and ophthalmological systems. These adverse effects are temporary and reduce without sequelae following the discontinuation of the drug. 1 Adverse effects in the musculoskeletal system are bone abnormalities and rheumatologic manifestations. 2 Seronegative spondyloarthropathy (SpA) like abnormalities including hyperosteosis, extraspinal calcifications, diffuse idiopathic skeletal hyperosteosis, bilateral and unilateral sacroiliitis, enthesopathy, costochondritis, and arthralgia, arthritis, myalgia, myopathy, vasculitis, and other complications have all been reported. 2 While arthralgia and myalgia are more common in case reports, sacroiliitis has been described as a rare side effect. [3][4][5][6] Herein, we report and describe the case of a 26-year-old female diagnosed with sacroiliitis after 8 weeks of isotretinoin treatment. CASE REPORTA 26-year-old female patient had used isotretinoin 30 mg daily for her facial acne for a period of 2 months, 2 years ago. After 8 weeks of isotretinoin treatment, she experienced inflammatory pain in her lower back and right hip region. Due to this pain, the isotretinoin treatment was ceased. While the lower back pain decreased, her right hip pain was persistent. She did not report any significant trauma and she had no histories of recent genitourinary or gastrointestinal infections. Her written inform consent was provided.Regarding physical examination, the lumbar flexion of the patient was normal and the sacroiliac stress test was positive on the right side. There were no enthesopathy, peripheral arthiritis, ocular findings, cutaneous lesions. The other locomotor and neurologic system findings appeared to be normal.Laboratory analysis showed that blood chemistry and complete blood count were in a normal range, while acute phase reactants including C-reactive protein and erythrocyte sedimentation levels were elevated [10.88 mg/dL (normal range: ≤0.5 mg/dL) and 87 mm/h (normal range: 0-20 mm/h), respectively]. These levels decreased to normal