Isotretinoin-induced Spondyloarthropathy-related Symptoms: A Prospective Study. 
Acne vulgaris is a chronic inflammatory disease involving the pilosebaceous unit of the skin.  Isotretinoin is a systemic retinoid that is often used as an effective treatment option for severe and treatment-resistant acne.  Isotretinoin may also cause rheumatologic symptoms.  The aim of this prospective observational study was to present followup results regarding the rheumatologic symptoms of patients who received systemic therapy for the treatment of acne (isotretinoin and tetracycline).  For inclusion in the study, all consecutive patients with acne who were aged > 18 years were evaluated by the same dermatologist.  The first 42 consecutive patients were included in the isotretinoin group, and after matching for age and sex, 32 consecutive patients were included in the tetracycline group.  Isotretinoin treatment was planned as an average dose of 30 mg daily and a total dose of 120-150 mg/kg for 4-6 months.  The patients were administered a dose of 1 g/day of tetracycline as 2 equal doses for 3 months.  Forty-two patients diagnosed with acne vulgaris were treated with isotretinoin 20.6 ± 4.4 (male/female: 17/22), and 32 patients were treated with tetracycline 20.6 ± 2.7 (male/female: 8/24).  There was no significant difference between the 2 groups with respect to age and sex.  Unilateral Achilles enthesopathy developed in 3 patients, whereas both Achilles enthesopathy and unilateral sacroiliitis developed in 1 patient.  Inflammatory back pain developed in 6 patients in the isotretinoin group.  To our knowledge, this was the first prospective observational study that assessed the rheumatologic symptoms of isotretinoin treatment.  The spondyloarthropathy findings were identified in 23.1% of the patients who used isotretinoin.