RENAL HEREDITARY TUBULOPATHIES: PHOSPHATE DIABETES (Two clinical cases)

Introduction. Phosphate diabetes is a representative of a group of diseases known as tubulopathies. It is more often of a hereditary nature. The disease manifests at an early age with symptoms similar to alimentary rickets, which creates problems for diagnosing and prescribing an adequate therapy. In this case, the current situation leads to the development of bone deformities and disability, delayed physical development, and the need for surgical treatment, which reduces the quality of life of the patients for a long time. Aim: To consider two clinical cases of phosphate diabetes with typical symptoms, demonstrate the diagnosing challenges, and analyze the treatment effects. Materials and Methods. Two clinical cases of phosphate diabetes are presented. The first patient: 16 years old, observed from the age of 2, and takes vitamin D and inorganic phosphates from the diagnosis date. The geneticist found the autosomal dominant of the pathology. The girl underwent two surgeries for her leg deformity. The second patient, 10 years old, was diagnosed at the age of 4 years. DNA diagnostics detected a mutation in the COL9A3 gene. They refused the complete DNA exome sequencing. From the diagnosis date, the patient is treated with the active vitamin D metabolite and inorganic phosphates. Results and Discussion. Clinician-observed: Patient 1 had leg deformities, painful legs, and disharmonious physical development caused by her growth retardation. Blood concentrations of calcium and phosphorus are within normal, there is hypocalciuria typical of phosphate diabetes in the urine, while phosphates are within normal. The patient’s kidney function is not impaired. Clinician-observed: Patient 2 is physically retarded, there are varus foot deformities and pes planovalgus feet. Kidney function is not impaired, the level of alkaline phosphatase is increased, the total blood calcium levels are decreased with phosphorus indicating normal values, and the urine phosphaturia and hypocalciuria are within normal ranges. Due to the COL9A3 mutation detected, Stickler syndrome was excluded. Orthopedic surgeon recommended surgical treatment of her leg deformities. Conclusions. The examination showed that the therapy allows keeping phosphate diabetes under control and avoiding the side effects of taking vitamin D.