X-linked hypophosphatemia is a genetic disorder caused by PHEX gene mutations, which affects the encoding of a metalloprotease whose function is to inhibit fibroblastic growth factor —23 (FGF-23), promoting phosphate renal loss. Following we describe the case of a teenager diagnosed with a PHEX gene mutation. The same genetic alteration was found in the mother of the patient, considering a spontaneous mutation that was transmitted to her son, which makes the case, even rarer, where the diagnostic challenge needs to overcome administrative, economic and social difficulties. A timely diagnosis and treatment could help optimize the finalheight and minimize the skeletal deformities presented in both the mother and the child. Currently, there is a traditional treatment and a novel one that was ordered for the pediatric patient in this report.