Congenital deficiency in alpha-fetoprotein

Congenital deficiency in alpha-fetoprotein (also known as congenital AFP deficiency or hereditary persistence of low AFP) is an extremely rare biochemical condition characterized by the absence or very low levels of alpha-fetoprotein (AFP) in fetal and neonatal blood. Alpha-fetoprotein is a glycoprotein normally produced in large quantities by the fetal liver and yolk sac during embryonic development. It is the dominant serum protein in early fetal life and plays roles in transport, immunomodulation, and growth regulation during development. This condition is primarily identified incidentally during routine prenatal screening, when maternal serum AFP levels are found to be unexpectedly low or undetectable. Congenital AFP deficiency does not appear to be associated with any consistent clinical phenotype or adverse health consequences in affected individuals. The condition itself is considered benign, and affected individuals are generally healthy. However, the absence of AFP during prenatal screening can cause diagnostic confusion, as low maternal serum AFP may prompt concern for chromosomal abnormalities such as trisomy 21 (Down syndrome), potentially leading to unnecessary invasive prenatal testing. The deficiency is caused by mutations in the AFP gene located on chromosome 4q25. No specific treatment is required for this condition, as it does not cause disease. Awareness of this entity is important primarily for genetic counselors and obstetricians to avoid misinterpretation of prenatal screening results. Genetic testing can confirm the diagnosis and provide reassurance to affected families.

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