Liver transplant as a curative treatment in a pediatric patient with classic homocystinuria: A case report

We report a patient with homocystinuria and hyperoxaluria who was cured of homocystinuria-related disease following liver transplant. The patient was diagnosed with homocystinuria as a newborn and was treated with dietary modifications and supplements. At 22 months, he passed a calcium oxalate stone and was found to have numerous bilateral kidney stones. Genetic testing confirmed primary hyperoxaluria, type 1. He underwent preemptive liver transplant at age four to treat primary hyperoxaluria. Following transplant, his serum methionine and homocysteine levels normalized, thus, demonstrating resolution of homocystinuria. Methionine and homocysteine levels remained normal 6 years later. Homocystinuria is associated with ophthalmologic, skeletal, neurologic, and thromboembolic complications. As cystathionine beta-synthase resides in the liver, transplant was hypothesized to be an effective treatment. Primary hyperoxaluria generally progresses to chronic kidney disease and is treated with combined kidney-liver transplant at the time of end stage kidney disease. Given this patient's dual diagnoses, we proceeded with preemptive liver transplantation. Three prior cases of patients with homocystinuria treated with liver transplantation have been reported. In all cases, transplant resolved metabolic effects. However, our case represents a pediatric patient without disease-related complications prior to transplant. This case supports liver-targeted gene therapies as an effective treatment for homocystinuria.