Salt-Losing 21-Hydroxylase Deficiency Caused by Double Homozygosity for Two "Mild" Mutations

Genetics of 21-hydroxylase deficiency: Clinical presentation should guide the investigation

A young couple applied for preconception counseling because of a case of congenital adrenal hyperplasia in the family. They were concerned about their risk of giving birth to a child with classic congenital adrenal hyperplasia. The case presented here demonstrates the complexity of the genetics of 21-hydroxylase deficiency and the way the clinical presentation should guide the genetic inquiry.

Assessing the risk of having a child with classic 21-hydroxylase deficiency: a new paradigm

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is a complicated condition genetically, clinically, and treatment wise. Genetically, there are numerus mutations with different effect on enzyme activity that make genetic diagnosis a challenge. Clinically, there are a wide range of presentations from asymptomatic patients to the severe life-threatening classic CAH. Both an asymptomatic heterozygote and a mildly affected non-classical patient can carry a 'severe' mutation and endow it to their offspring. We present a case of non-classic CAH and discuss the problematic relations between biochemical and genetic diagnosis. By integrating the seemingly contradicting literature, we provide a new simple tool to assess the risk of such patients to give birth to a child with classic CAH.