ESPE Abstracts

Introduction: X Linked hypoposphatemic rickets (XLH) is a rare genetic disorder characterized by variable clinical features. It is often misdiagnosed with other types of rickets. A novel effective treatment is currently available. We report four cases of XLH who presented to our centre over a period of five years and describe their clinical presentation, diagnostic, treatment challenge and outcome.

CASE 1 -The child presented with short stature and progressive genu valgus deformity from the age of 18 months. She is born to first degree cousin parents. Mother is 142 cm tall but had no skeletal deformities. The patient was diagnosed with vitamin D deficiency and had surgery for deformity correction. At 5 years of age, she was diagnosed with hypophosphatemic rickets. She had a normal PTH and active vitamin D with high FGF23. Genetic testing confirmed mutation in PHEX gene. She was initially started on conventional treatment, then shifted to Burosumab which resulted in normalizing serum phosphate and improving her rickets score and stature.

CASE 2 - She presented with severe bowing of legs from the age of 14 months. She had a progressive genu varum deformity with rachitic rosary and wrist widening. She had classical biochemical features of XLH with high FGF23. She was genetically confirmed to be having a heterozygous mutation of PHEX gene. She was started on conventional treatment with oral phosphate and 1- alpha calcidiol at 2year of age. Her response is suboptimal with improvement of phosphate level but persistence of ricketic changes and deformity.

CASE 3 -18-month-old boy was referred for low phosphate levels detected during a febrile illness. He was born by Caeserean section as mother had deformed bones. The child had delayed motor milestones with abnormal head shape. At presentation, he had no bone deformities. Genetic testing confirmed a homozygous mutation variant of PHEX gene. He was started on Burosumab.

CASE4 - A 39-year-old woman presented to our clinic as mother of patient case 3 (A). She was diagnosed as osteogenesis imperfecta and underwent multiple bilateral femoral and tibial corrective osteotomies. She is 131 cm tall. She lost all her teeth and is using a fixed denture. Genetic testing a showed a heterozygous mutation of PHEX mutation.

Conclusion: XLH has a variable presentation and can be misdiagnosed leading to deterioration of the bone condition and deformity. High index of suspicion is important for proper diagnosis and effective treatment.