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Hypodontia-dysplasia of nails syndrome
Hypodontia-nail dysplasia syndrome is a form of ectodermal dysplasia.
Its incidence has been estimated at around 1-2 in 10,000.
The primary teeth are usually normal but the permanent teeth often fail to erupt. The mandibular incisors, second molars, and maxillary canines are frequently absent and the crowns may be small and conical. Lip eversion may be present. Nails are usually small, thin and brittle with longitudinal ridges, pitting and koilonychias. Congenital absence of the nail plate has also been reported. Toenails are usually more severely affected than fingernails. Sweat glands, heat tolerance and hair are normal, although fine hair has been described in some cases.
The syndrome is caused by a mutation in the MSX1 gene (4p16.1).
Diagnosis is usually made during mid-childhood when persistence of the primary dentition becomes apparent, but the syndrome may be difficult to diagnose as the nail defects may be mild.
The differential diagnosis should include other forms of ectodermal dysplasia, in particular hypohidrotic ectodermal dysplasia (see these terms).
Transmission is autosomal dominant.
Management and treatment
There is no specific treatment but oral health care and dental management are recommended.
The prognosis is good. The nail defects usually become less apparent with age and the nails often appear normal by adulthood.