B9D2-related disorders are extremely rare genetic conditions caused by changes in a gene called B9D2. These disorders lead to several birth defects that affect the brain, kidneys, and limbs. Common features include problems in brain development, extra fingers or toes, and cysts in the kidneys or liver.
So far, only four families have been found with these disorders—two families had Meckel syndrome and two had Joubert syndrome.
B9D2