Poorly Controlled Homocystinuria: A Rare Cause of Ischemic Priapism?

Sexual Medicine
Mark JohnsonDavid Ralph

Abstract

We report on the 1st case of ischemic priapism secondary to poorly controlled homocystinuria. Homocystinuria is a rare, autosomal recessive, inherited disorder of metabolism that is caused by a deficiency of cystathionine synthase, leading to marked hyperhomocysteinemia. Arterial and/or venous thromboemboli are a major cause of mortality and morbidity in patients with homocystinuria. Untreated patients have a 50% chance of having a vascular event by 30 years of age. Increased homocysteine levels have been reported to upregulate prothrombotic factors and downregulate antithrombotic factors; in particular, increased homocystinuria has been found to downregulate nitric oxide (NO). Mice that are deficient in NO synthase in the cavernosal smooth muscles have a higher incidence of priapism. Decrease in NO synthase causes downregulation of cyclic guanosine monophosphate, phosphodiesterase type 5A, and Rho A/Rho-kinase. Because persistently increased homocysteine also downregulates NO, a similar mechanism could be proposed for priapism secondary to homocystinuria. In patients presenting with priapism, specific features of homocystinuria should be sought; in selected patients, screening with plasma total homocysteine might be appropriat...Continue Reading

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