Long-term complications of systemic oxalosis in children-a retrospective single-center cohort study

Systemic oxalosis is a severe complication seen in primary hyperoxaluria type I patients with kidney failure. Deposition of insoluble calcium oxalate crystals in multiple organs leads to significant morbidity and mortality.

We describe a retrospective cohort of 11 patients with systemic oxalosis treated at our dialysis unit from 1982 to 1998 (group 1) and 2007-2019 (group 2). Clinical and demographic data were collected from medical records. Imaging studies were only available for patients in group 2 (n = 5).

Median age at dialysis initiation was 6.1 months (IQR 4-21.6), 64% were male. Dialysis modality was mostly peritoneal dialysis in group 1 and daily hemodialysis in group 2. Bone disease was the first manifestation of systemic oxalosis, starting with the appearance of sclerotic bands (mean 166 days, range 1-235), followed by pathological fractures in long bones (mean 200.4 days, range 173-235 days). Advanced disease was characterized by vertebral fractures with resulting kyphosis, worsening splenomegaly, and adynamic bone disease. Two patients developed pulmonary hypertension, 4 and 8 months prior to their death. Four of 11 patients developed hypothyroidism 0-60 months after dialysis initiation. Only one patient survived after a successful liver-kidney transplantation. Four patients died after liver or liver-kidney transplantation.

This is the first comprehensive description of the natural history of pediatric systemic oxalosis. We hope that our findings will provide basis for a quantitative severity score in future, larger studies.