Is Paroxysmal nocturnal hemoglobinuria hereditary?

Paroxysmal nocturnal hemoglobinuria (PNH) is a genetic condition but it is not hereditary, meaning it is not passed from parents to children. It is caused by an acquired somatic mutation in the PIGA gene that occurs after conception, rather than an inherited germline mutation present in every cell of the body.

Why is Paroxysmal nocturnal hemoglobinuria considered genetic but not hereditary?

To understand Paroxysmal nocturnal hemoglobinuria, it is essential to distinguish between "genetic" and "hereditary." A disease is genetic if it involves a change in DNA. A disease is hereditary only if that DNA change is passed down through reproductive cells (sperm or eggs) from parents to offspring. Paroxysmal nocturnal hemoglobinuria arises from a somatic mutation, which means the error occurs in a hematopoietic stem cell (a blood-forming cell) during an individual's lifetime. Because this change is confined to the blood cell lineage and not the germline, Paroxysmal nocturnal hemoglobinuria cannot be passed to children.

What causes the mutation in Paroxysmal nocturnal hemoglobinuria?

The development of Paroxysmal nocturnal hemoglobinuria is linked to a somatic mutation in the PIGA gene, located on the X chromosome. This gene is responsible for producing a protein necessary for the attachment of protective proteins to the surface of blood cells. When these protective proteins are missing, the immune system’s complement system attacks and destroys the red blood cells. While the exact trigger for this spontaneous mutation remains a subject of ongoing medical research, it is not considered a familial or inherited trait.

Is genetic testing recommended for families of patients?

Because Paroxysmal nocturnal hemoglobinuria is not inherited, genetic testing of family members is generally not recommended or necessary. There is no risk of passing the condition to offspring, and there is no evidence that family members are at an increased risk of developing the disease due to shared genetics. Diagnostic testing for Paroxysmal nocturnal hemoglobinuria is performed on the patient’s blood, typically using flow cytometry to look for the absence of specific surface proteins (like CD55 and CD59) on blood cells, rather than traditional germline genetic sequencing.

What is the role of genetic counseling in this condition?

While Paroxysmal nocturnal hemoglobinuria is not hereditary, genetic counseling can still be a valuable resource for patients. A genetic counselor can help clarify the nature of somatic mutations, alleviate concerns regarding family planning, and explain why the condition does not follow typical Mendelian inheritance patterns. The 162 members of the Paroxysmal nocturnal hemoglobinuria community on DiseaseMaps.org often find that understanding the distinction between acquired and inherited conditions provides significant relief to those worried about the health of their children.

Key facts about the genetics of Paroxysmal nocturnal hemoglobinuria

• Inheritance: None; the condition is acquired, not inherited.


• Gene Involved: PIGA gene mutation.


• Cell Type: Somatic (non-reproductive) hematopoietic stem cells.


• Risk to Children: 0% (the same as the general population).


• Diagnostic Standard: Flow cytometry is the gold standard, not germline genetic testing.

Next steps

• Consult with a hematologist who specializes in bone marrow failure syndromes and Paroxysmal nocturnal hemoglobinuria.


• Connect with the 162 other patients in the DiseaseMaps.org community to share experiences and coping strategies.


• Request a referral to a genetic counselor if you have lingering concerns about family history or the nature of your diagnosis.


• Stay updated on the latest clinical research through the Aplastic Anemia & MDS International Foundation (AAMDSIF).

Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions regarding a medical condition.

References

• National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD): Paroxysmal nocturnal hemoglobinuria.


• Orphanet: Paroxysmal nocturnal hemoglobinuria (ORPHA:732).


• Online Mendelian Inheritance in Man (OMIM): #300818 (PIG-A).


• Aplastic Anemia & MDS International Foundation (AAMDSIF): Understanding PNH.