Is Succinic semialdehyde dehydrogenase deficiency hereditary?

Succinic semialdehyde dehydrogenase deficiency (SSADH deficiency) is a rare, hereditary metabolic disorder caused by mutations in the ALDH5A1 gene. It follows an autosomal recessive inheritance pattern, meaning both parents must be carriers of a non-working gene copy for a child to be affected, resulting in a 25% risk of inheritance for each pregnancy.

Is Succinic semialdehyde dehydrogenase deficiency hereditary?

Yes, Succinic semialdehyde dehydrogenase deficiency is strictly a genetic and hereditary condition. In clinical genetics, "genetic" refers to the fact that the disease is caused by a change in DNA, while "hereditary" indicates that this change is passed down through families. Succinic semialdehyde dehydrogenase deficiency is caused by pathogenic variants in the ALDH5A1 gene, which provides instructions for making an enzyme that breaks down gamma-aminobutyric acid (GABA). When this enzyme is absent or non-functional, GABA and its derivative, 4-hydroxybutyric acid (GHB), accumulate in the body, leading to the neurological symptoms associated with Succinic semialdehyde dehydrogenase deficiency.

What is the inheritance pattern of Succinic semialdehyde dehydrogenase deficiency?

Succinic semialdehyde dehydrogenase deficiency is inherited in an autosomal recessive pattern. This means that an affected individual must inherit two copies of the mutated gene—one from each parent. Parents of an affected child are typically asymptomatic "obligate carriers," meaning they each carry one mutated copy of the ALDH5A1 gene. Because this is a recessive condition, de novo (spontaneous) mutations are extremely rare; almost all diagnosed cases are inherited from carrier parents.

How is Succinic semialdehyde dehydrogenase deficiency diagnosed genetically?

Genetic testing is the gold standard for confirming a diagnosis of Succinic semialdehyde dehydrogenase deficiency. While biochemical testing often shows elevated levels of 4-hydroxybutyric acid in urine, molecular genetic testing is required to identify the specific mutations in the ALDH5A1 gene. Recommended testing approaches include:

• Targeted mutation analysis: If a known family mutation has already been identified.


• Full gene sequencing: Examining the entire ALDH5A1 sequence to identify pathogenic variants.


• Deletion/duplication analysis: To detect larger genetic changes that standard sequencing might miss.

Why is genetic counseling recommended for families?

Genetic counseling is vital for families affected by Succinic semialdehyde dehydrogenase deficiency because it provides clarity on recurrence risks and family planning. A genetic counselor can assist in identifying other family members who may be carriers, as siblings of an affected individual have a 66% chance of being carriers themselves. For couples who are both known carriers, the following options are often discussed during counseling sessions:

1. Preimplantation Genetic Testing (PGT): Screening embryos during IVF to select those without the ALDH5A1 mutations.


2. Prenatal Diagnosis: Using amniocentesis or chorionic villus sampling (CVS) during pregnancy to test the fetus.


3. Carrier Testing: Assessing extended family members to determine their genetic status.

With 13 members currently sharing their experiences on DiseaseMaps.org, connecting with our community can provide emotional support alongside these clinical discussions.

Next steps

• Consult with a metabolic geneticist or a certified genetic counselor to discuss your family history and testing options.


• If you have a confirmed diagnosis, consider joining the DiseaseMaps.org community to connect with other families navigating Succinic semialdehyde dehydrogenase deficiency.


• Request a referral to a metabolic center that specializes in rare neuro-metabolic disorders for comprehensive management.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of a qualified healthcare provider with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Succinic semialdehyde dehydrogenase deficiency.


• Orphanet: Succinic semialdehyde dehydrogenase deficiency (ORPHA:3197).


• OMIM (Online Mendelian Inheritance in Man): ALDH5A1 gene entry (#271980).


• National Library of Medicine (PubMed): Clinical reviews on ALDH5A1-related disorders.