Cornelia de Lange syndrome occurs in about one in 20,000 births and is characterized by mental retardation, short stature, limb abnormalities, and distinctive facial features. Most cases are sporadic, and may represent new autosomal dominant mutations. In some cases a deletion on chromosome 3p26 has been indentified.
Cowden syndrome is an autosomal dominant tumor syndrome characterized by multiple hamartomas and a risk of breast, thyroid, and uterine tumors (both benign and malignant). The most common feature of cowden are skin bumps(trichilemmomas) or wart-like growths (papillomatous papules). Most cases of cowden are caused by a change in a tumor suppressor gene PTEN.
Russell-Silver syndrome, due to many different genetic reasons, is characterized by growth problems, short stature, certain facial features, body asymmetry, and normal intellegence. Most cases are sporadic, but some are seen with different chromosome abnormalities such as rearrangments of chromosome 17, or inheriting two copies of chromosome 7 from the mother.