<unk>  is inherited in an autosomal dominant manner, needing only one copy of the defective gene to cause the disorder. The cause of the disorder has been linked to an 11 base pair deletion in exon four of the PTPN11 gene (12q24.13). This deletion causes a frameshift, resulting in a nonsense mutation with a premature stop codon. This causes severe truncation and loss of function in the gene’s protein product, tyrosine phosphatase SHP-2. SHP-2 plays an important role in regulating expression of the Indian Hedgehog gene (IHH), which is associated with differentiation in chondrocytes (specialized cells in cartilage tissue). Individuals affected by<unk>  generally demonstrate high levels of IHH expression, which is believed to be responsible for the tumor growth. Given that the mutation causes a loss of protein function and displays a dominant inheritance pattern, it is hypothesized that individuals homozygous for the disorder would display greater symptoms than heterozygous individuals, though insufficient data is available to evaluate these claims due to the rarity of the disease. Conversely, some heterozygous individuals have shown minimal effects, leading to the disorder’s designation as incompletely penetrant. The cause of this is not fully understood, but may be due to other factors influencing IHH expression.
Metachondromatosis
Verruciform xanthoma
Pseudoxanthoma elasticum
Warty dyskeratoma
Boomerang dysplasia
Phakomatosis
Neuroma cutis
Diffuse infantile fibromatosis