label: hyper-IgM syndrome type 1
label_lc: hyper-igm syndrome type 1
description: The X-linked variant of the Hyper-IgM syndrome. The affected individuals are virtually always male, because males only have one X chromosome, received from their mothers. Their mothers are not symptomatic, even though they are carriers of the allele, because the trait is recessive. Male offspring of these women have a 50% chance of inheriting their mother's mutant allele.