Hyperoxaluria is a rare autosomal recessive disease based on a congenital metabolic disorder of oxalates. According to the data of the national registers of the USA, Europe, Japan, this pathology is less than 1%. The purpose is to demonstrate clinical observation, requiring early diagnosis of the disease and addressing the type and timing of organ transplantation. Clinical observation. Boy A.A. 14 years from a kindred marriages, 5th pregnancy, 3 births. Birth weight 4000 grams, body length 57 cm. In the early period and subsequent history, growth retardation is noted. In the anamnesis – from both mother's and father's side, cases of urolithiasis with a terminal outcome. The debut of disease since May 2012, previously has not been examined. The reason for hospitalization: the edema in the lower extremities and decreased amount of urine. Results of the examination established the terminal stage of chronic kidney disease requiring renal replacement therapy (CKD, stage 5D). Stage 1 anemia, accelerated ESR up to 43 mm/h, hyperazotemia, hypocalcemia, hyperphosphatemia, increase in parathyroid hormone level to 699-1116 pg/ml. Signs of PED – lag of physical development: height-138cm, weight-38.5kg, BMI - 20.2, total plasma protein - 67.9 → 48 g/l. Arterial hypertension - 150/90 mmHg. According to the results of computed tomography: the kidneys are reduced in size, tuberous, in the lumen there are multiple calculi: the maximum diameter is 0.9 cm, the echogenicity on both sides is increased. Sessions of programmed hemodialysis were started for 4 hours three times a week. After 6 months, by perseverance of parents, an operation was performed - allograft of a donor kidney (donor is the patient’s sister), however, a month later an early allograft rejection was noted. The results of a molecular genetic study from 21.08.2013 at the Mayo Clinic Hyperoxaluria Center (USA) revealed mutation 1: c.33_34insC, p.P11fs33X, mutation 2: c.33_34insC, p.P11fs33X, which corresponds to type I hyperoxaluria. In the spring of 2014, the patient was treated at the Fortis Memorial Research Institute clinic (Gurugram, India), and on 20.08.2014 despite the indication of immunogenetic data and the need for kidney and liver transplantation, a second kidney transplantation was performed in a hospital in India (donor is the father of the child ) The postoperative period proceeded with complications. The patient was discharged from a clinic in India to continue treatment at the place of residence. In admission to the Center of Nephrology and ECDofUC, the condition was regarded as very severe due to multiple organ failure, decompensation of all vital functions, due to the progression of type 1 hyperoxaluria. Despite ongoing therapeutic measures, the child died. Cause of death: Progressive multiple organ failure: cardiovascular failure, respiratory failure, renal failure. The leading manifestations of primary type 1 hyperoxaluria in this case were: the development of ESRD with urolithiasis, kindred marriages, cases of urolithiasis with a terminal outcome in the family, data from a molecular diagnostic study revealing a characteristic gene mutation.