Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
KFSD is usually caused by an alternation in the MBTPS2 gene. Some studies suggest that an alternation in the SAT1 gene causes this form of KFSD as well. This form of KFSD is called X-linked keratosis follicularis spinulosa decalvans (KFSDX) and follows an X-linked recessive inheritance pattern.
X-linked genetic disorders are conditions caused by an abnormal gene on the X chromosome and manifest mostly in males. Females that have an abnormal gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms because females have two X chromosomes and only one carries the abnormal gene. Males have one X chromosome that is inherited from their mother and if a male inherits an X chromosome that contains an abnormal gene he will develop the disease.
Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease and a 25% chance to have an unaffected son.
If a male with an X-linked disorder is able to reproduce, he will pass the abnormal gene to all of his daughters who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring.
Some families with KFSD are reported to have male to male transmission, which suggests autosomal dominant inheritance. In these families, sons inherited KFSD from their father. All males in the family are affected by KFSD. All females do not have KFSD. The gene that causes KFSD in these families is not known.
Rarely, patients with KFSD do not have any family history of KFSD. More research is needed to understand what gene causes KFSD in these families.