Phosphoserine Phosphatase Deficiency

What else is it called?


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What causes it?

3-Phosphoserine phosphatase deficiency is an extremely rare form of serine deficiency syndrome. This condition is caused by mutations to the PSPH gene. PSPH provides instructions for the PSPH enzyme that catalyses the final and irreversible step of the amino acid L-serine’s synthesis.

Serine’s function is to help form the phospholipids which are necessary for creating every cell in the human body. In addition, this amino acid is involved in the functioning of RNA and DNA, in the muscle formation as well as in the maintenance of a proper immune system. If your body is unable to metabolism serine then this may lead to potential health consequences.

How common is it?

Due to the rareness of this condition it is difficult to state how many people currently have/had this condition and whether it is more prevalent in males or females or specific ethnicities.

What are the signs and symptoms?

PSPHD results in pre- and postnatal growth retardation, moderate psychomotor retardation and facial features suggestive of Williams syndrome. However, previous research suggests that this condition more commonly presents in infancy. Some of the other conditions that your child may have are:

  • Seizures
  • Hypertonia
  • Feeding difficulties
  • Global development delay
  • Cerebral atrophy (rare)
  • Hyposerinemia

How is it diagnosed?

Plasma levels of serine and glycine have been reported to have been reduced in blood sample analysis from previous research. Therefore, this condition may be diagnosed via a urine or blood sample to check the level of metabolites present within your child’s body.

This condition will also be diagnosed with genetic testing, this can be done pre-natal if you have a history of this condition within your family history. This will be discussed with your doctor if they consider your child to have this condition.

Can it be treated?

Treatment for this condition is aimed at managing the symptoms as they appear such as seizures. Previous literature suggests that treatment with oral serine led to normalization of serine levels and some improvement in head growth.

Do my family need to be tested?

PSPHD can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.

If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.

If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.

Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inheritedPSPHD. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own.

If you have previously had a child with PSPHD and go on to have further children, their New-born Screening test should be carried out within 24-48 hours of birth.

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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