Hereditary Orotic Aciduria: A Patient Guide

Hereditary Orotic Aciduria (HOA), also known as UMPS deficiency, is an exceptionally rare genetic condition that affects how the body creates the most basic building blocks of life. This guide is written primarily for parents and caregivers of children diagnosed with HOA, though the information is also relevant for adults managing the condition. In children with HOA, pathogenic variants in the UMPS gene prevent the body from producing enough pyrimidines, which are essential components needed to build DNA and RNA ^[1]. Because these building blocks are required for every cell in the body to grow and divide, a shortage can lead to significant health challenges, particularly in systems that rely on rapid cell production, such as the bone marrow and the developing brain ^[2].

This condition is inherited in an autosomal recessive manner, meaning a child must inherit a mutated gene copy from both parents to be affected ^[3]. Without treatment, the impaired availability of pyrimidines causes the body to struggle with physical growth and the production of healthy blood cells. This typically manifests as megaloblastic anemia—a condition where red blood cells are abnormally large and inefficient, reducing the blood’s overall oxygen-carrying capacity—alongside potential issues like a weakened immune system, slow physical development, and neurological delays ^[4]. Because the body cannot complete the process of making these building blocks, a substance called orotic acid builds up and is released in the urine, which serves as a key marker for diagnosis ^[5].

While the rarity of HOA can feel isolating, the modern outlook for children treated early is encouraging. In certain regions where expanded newborn screening programs include orotic acid (such as a specific program in Israel), cases have been identified early, allowing for intervention before symptoms even begin ^[5]. Note that newborn screening for HOA is not universally available.

The standard of care involves therapy with uridine triacetate, which provides the body with the exact building blocks it is unable to make on its own ^[6]. By bypassing the genetic blockage, this treatment can improve anemia, support normal growth, and prevent many complications. While individual prognoses and long-term neurological outcomes remain variable and depend heavily on early detection, many patients treated early have excellent hematologic and growth outcomes ^[4].