Type I collagen N-telopeptide variation in adolescents receiving oral isotretinoin for severe acne

The prolonged use of retinoids has been reported to be associated with changes of bone biochemical markers and toxic skeletal effects. Among collagen markers, type I collagen N-telopeptide (NTx) is present in all tissues that contain type I collagen, mostly in bone and in cutaneous tissue. It is a reliable indicator of bone resorption in metabolic bone disease, but has not previously been investigated in dermatological diseases during retinoid therapy. Isotretinoin, a synthetic 13-cis-retinoic acid, is highly effective in the treatment of severe acne vulgaris. We evaluated the effect of low-dose short-term oral isotretinoin treatment on bone remodeling markers in 10 adolescents (mean age 17.8 years) affected by severe acne. We measured urinary NTx as a marker of bone resorption, alkaline phosphatase (ALP) and osteocalcin (OC) as markers of bone formation, parathyroid hormone (PTH) and metabolites of vitamin D (25OH-D3 and 1,25(OH)2D3). Clinical and laboratory tests were performed before and after three months of isotretinoin treatment at the dosage of 0.5 mg/kg/day. All patients showed a good clinical response to the treatment (7/10 marked improvement, 3/10 mild improvement). No changes were detected in serum PTH, 25OH-D3, 1,25(OH)2D3, OC and ALP, while urinary NTx concentrations were significantly reduced (p < 0.05). In conclusion, the lack of change in PTH, OC, ALP and vitamin D metabolites and the absence of increase of NTx suggest no bone effect of the isotretinoin treatment. The decrease of urinary NTx could be due to the effect of isotretinoin on the cutaneous component of type I collagen. Severe acne in the active inflammatory phase could change the levels of this marker. Thus, short-term low-dose oral isotretinoin is an effective and safe treatment for severe acne.