Achondroplasia is a common cause of dwarfism. It occurs as a sporadic mutation in approximately 80% of cases (associated with advanced paternal age) or it may be inherited as an autosomal dominant genetic disorder.Wikipedia
Achondroplasia mutations are known from the FGFR3 gene.
Inheritance: Autosomal dominant; 80 percent arise from de novo mutations.
Penetrance: 100 percent
Mutations of two types in one SNP in the FGFR3 gene, rs28931614, account for greater than 99 percent of cases of achondroplasia. Interestingly, rs28931614 may be one of the most mutable DNA positions in the genome.