X-linked hypophosphatemic rickets: case report

Abstract

INTRODUCTION: The X-linked hypophosphatemic rickets is considered the most common cause of rickets. It is an X-linked dominant disease, caused by a PHEX gene mutation. It is believed that the biochemical and bone mineralization changes because of the increase of phosphaturic factor, resulting from the PHEX genes inability to inactivate its substrate. CASE REPORT: A seven-year and eleven-month-old girl has been followed by an orthopedist since she was 1 year old, due to lower limb deformity. She was referred to a pediatric endocrinologist for further evaluation. At clinical examination, the patient presented genu varum and Z score of stature/age = 4.8. Laboratory tests: serum phosphorus = 2.3mg/dl (4.5-6.6), ionic calcium = 1,8mmol/l (1.17-1.32), parathyroid hormone = 42pg/ml (12-88), alkaline phosphatase = 600U/L (<300). The patient has always shown low adherence to treatment. Currently, at age 12 and 2 months old, endures with genu varum and short stature, besides the persistence of laboratory alterations. The PHEX gene sequencing, that evidenced a heterozygous mutation on that gene, confirming the X-linked hypophosphatemic rickets diagnosis. COMMENTS: The X-linked hypophosphatemic rickets is a rare disease with clinical manifestations observed since the early years of life. Diagnosis and intervention are important to decrease these patients morbimortality. The patient started follow-up at our service belatedly, with bone deformity and short stature, resulting in low treatment adherence. For these reasons, there wasnt any clinical or laboratory improvement during that time.