Pyrimidine 5 Nucleotidase Deficiency

What else is it called?

  • P5’N-1 Deficiency 
  • UMPH1 deficiency 
  • Uridine 5′-monophosphate hydrolase deficiency 
  • Acquired Pyrimidine 5 Nucleotidase Deficiency 

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What causes it?

This disorder is caused by a problem in the P5’N gene. This gene produces the P5’N-1 enzyme which is involved in the production of red blood cells in the body. This process is needed to carry oxygen around the body through the bloodstream, and to remove carbon dioxide. 

If you have a problem in the P5’N gene, you will not produce enough of the P5’N-1 enzyme. Therefore, you will be unable to produce enough red blood cells, and your body will be unable to absorb enough oxygen to function properly. 

You may have been diagnosed with Acquired Pyrimidine 5 Nucleotidase Deficiency. Although it has the same presentation and symptoms, it is typically caused by lead poisoning. It has also been found in certain types of cancer, specifically leukaemia and lymphoma. 

How common is it?

The amount of people diagnosed with Pyrimidine 5 Nucleotidase Deficiency is uncertain because many cases are presumed to go undetected. However, over 60 cases have been reported worldwide. 

Due to the small amount of diagnosed cases, there is no concrete information on whether the disorder affects certain groups of people more than others. 

What are the signs and symptoms?

Symptoms usually begin in early childhood. The main symptom of Pyrimidine 5 Nucleotidase Deficiency is chronic haemolytic anaemia. This occurs when there you have a low red blood cell count in your blood. For Pyrimidine 5 Nucleotidase Deficiency, this happens because your body is destroying the red blood cells quicker than you can produce them. This can cause a number of physical symptoms, such as: 

  • Extreme, constant tiredness (fatigue) 
  • Dizziness 
  • Heart palpitations  
  • Confusion 
  • Jaundice 
  • An enlarged spleen (splenomegaly) or liver (hepatomegaly) 

Most people with Pyrimidine 5 Nucleotidase Deficiency will experience a mild to moderate level of haemolytic anaemia. In extreme cases, some people will develop a fever, pain in the back and abdomen, and shock. Pyrimidine 5 Nucleotidase Deficiency can also cause learning difficulties and mild developmental delays. 

If left untreated, Pyrimidine 5 Nucleotidase Deficiency may lead to serious heart problems. Although this in itself may cause a reduced life expectancy, many people with the disorder have a typical life expectancy. 

How is it diagnosed?

Pyrimidine 5 Nucleotidase Deficiency can be diagnosed through a specialised blood test. A genetic test may also be required. 

It may be the case that you are diagnosed with chronic haemolytic anaemia first, and then receive a diagnosis of Pyrimidine 5 Nucleotidase Deficiency later on. 

Pyrimidine 5 Nucleotidase Deficiency is not currently part of the newborn screening process. However, anaemia may be identified during your child’s newborn blood spot test (also known as the heel prick test). 

Can it be treated?

Current treatment for Pyrimidine 5 Nucleotidase Deficiency focuses on reducing and managing the symptoms. This may include occasional blood transfusions (although some rare cases may require regular transfusions), medication, and/or lifestyle changes (for example, a diet or exercise plan). Your medical team may also recommend removing your spleen to ease the symptoms of anaemia, although this has been shown to have a limited effect on the condition. 

There is currently no cure for Pyrimidine 5 Nucleotidase Deficiency, however many people with the disorder live long and fulfilling lives. 


Do my family need to be tested?

Pyrimidine 5 Nucleotidase Deficiency is an autosomal recessive disorder, which means that it is inherited from both parents, who are carriers of the disorder through their genes. 

All genes come in pairs. Carriers of Pyrimidine 5 Nucleotidase Deficiency have one working P5’N gene and one faulty gene. Children inherit one gene from each parent to make their pair. Whether they have Pyrimidine 5 Nucleotidase Deficiency depends on what genes inherit: 

  • There is a 50% chance that the child will inherit one faulty and one working gene, which means they will also be a carrier. 
  • There is a 25% chance that the child will inherit two working genes and not inherit or carry the faulty gene. 
  • There is a 25% chance that the child will inherit two faulty genes, which means they will have Malonyl CoA Decarboxylase Deficiency. 

If you think somebody in your family may have Pyrimidine 5 Nucleotidase Deficiency, or that you may be a carrier, contact your medical team who may refer you for genetic testing. 

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: AAP002]. 

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