Young Simpson syndrome

Young Simpson syndrome (YSS), is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, mental retardation and postnatal growth retardation.

Other symptoms include transient hypothyroidism, macular degeneration and torticollis. The condition was discovered in 1987 and the name arose from the individuals who first reported the syndrome. A individual with YSS has been identified with having symptoms to a similar syndrome known as Ohdo Blepharophimosis syndrome showing that it is quite difficult to diagnose the correct condition based on the symptoms present. Some doctors therefore consider the syndrome to be the same.

The mode of inheritance has had mixed findings based on studies undertaken. One study showed that the parents of an individual with YSS are unrelated and phenotypically normal, indicating a sporadic mutation, thus making it difficult to base the cause of the condition on genetic make up alone. Another study however with an individual of YSS had first cousins as parents, giving the possibility of autosomal recessive inheritance.

KAT6B
In 2011, it was demonstrated that de novo mutations in the gene KAT6B caused  YSS.