Clinical Features and Genetic Diversity of Primary Hyperoxaluria: A Case Series Analysis of Chinese Patients

INTRODUCTION: This study aimed to characterize the clinical features, genetic profiles, and outcomes of primary hyperoxaluria (PH) in a Chinese cohort. METHODS: We retrospectively reviewed patients diagnosed with PH between 2008 and 2025 at our institution. Diagnosis was established through genetic analysis or histopathological findings combined with clinical manifestations and positive family history. Clinical, laboratory, genetic, imaging, histopathological, treatment, and outcome data were collected. RESULTS: Thirteen patients were included (PH1, n=7; PH2, n=3; PH3, n=2; unclassified, n=1). Median ages at symptom onset and diagnosis were 7 and 21 years, respectively. Renal involvement manifested as urolithiasis (92.3%) and nephrocalcinosis (30.8%). At diagnosis, the overall median serum creatinine was 335 µmol/L, and the median 24-hour urinary oxalate excretion was 0.8 mmol/1.73m² (n = 6). Systemic oxalate deposition was observed in 30.8% of patients, predominantly affecting bone and heart. Five previously unreported genetic variants were identified. Treatment consisted of supportive care, with vitamin B6 for PH1. Over a median follow‑up of 13.0 years, 100% of PH1 and 66.7% of PH2 patients progressed to end-stage renal disease, with two infantile-onset PH1 patients demonstrating rapid progression; conversely, PH3 patients preserved renal function (chronic kidney disease stage 1). Three PH1 patients developed recurrent oxalate nephropathy following isolated kidney transplantation. The overall mortality was 15.4%. CONCLUSIONS: PH commonly presents with non-specific symptoms of urolithiasis, frequently resulting in diagnostic delay. PH1 is associated with a more severe clinical course than other subtypes, particularly in infantile-onset cases. This study expands the known genetic variant spectrum and underscores the importance of early genetic diagnosis.