X-linked hypophosphatemic rickets with advanced bone age treated with aromatase inhibitor

SUMMARY: We present an adolescent with X-linked hypophosphatemic rickets (XLH) with bone age advancement and its response to aromatase inhibitors (AIs). A male with XLH, confirmed with a deletion on the PHEX gene, received regular treatment since the first year of life with average growth velocity and height. He had bone age compatible with chronological age until 13 when he had a bone age advancement and a decrease in the predicted final height thought to be due to initiation of oral isotretinoin, which has been previously reported. Then, anastrozole was initiated and maintained concomitant to the rickets treatment for 2 years with bone age stabilization. He had no adverse effects or worsening of bone health markers. As a result, he maintained his height gain and improved his final height Z score compared with the predicted final height at initiating anastrozole. In conclusion, although AIs was a reasonable strategy to stabilize bone age and minimize height impairment, careful monitoring is mandatory to understand its benefits and effects on XLH patients. LEARNING POINTS: Although X-linked hypophosphatemic rickets patients have normal puberty, they can be affected by metabolic and environmental factors that may advance their bone age and impair the predicted final height, similar to the general population. Isotretinoin may accelerate skeletal maturation during puberty in an adolescent with X-linked hypophosphatemic rickets. Aromatase inhibitors showed to be a reasonable strategy to stabilize bone age and minimize height impairment in an adolescent with X-linked hypophosphatemic rickets.