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Autosomal dominant deafness-onychodystrophy syndrome
Dominant deafness-onychodystrophy (DDOD) syndrome is a multiple congenital anomalies syndrome characterized by congenital hearing impairment, small or absent nails on the hands and feet, and small terminal phalanges.
ORPHA:79499Classification level: Disorder
The prevalence is unknown but it has been reported in 22 individuals from ten families to date.
The main clinical characteristics of DDOD syndrome are severe sensorineural hearing loss or deafness and onychodystrophy (small or absent fingernails and toenails, sometimes limited to the nails of the first and fifth digits). Brachydactyly, long, finger-like or tri-phalangeal thumbs as well as conical, hypoplastic teeth or oligodontia (see this term) have also been reported in several patients. Syndactyly, minor facial dysmorphism (mild hypotelorism, deep set eyes and midface hypoplasia), and epilepsy have been seen in individual cases. Unlike DOORS syndrome (see this term), DDOD patients follow a normal development and have normal intelligence.
DDOD syndrome is caused, in some cases, by heterozygous mutations in the ATP6V1B2 gene (8p21.3) encoding a vacuolar ATPase (V-ATPase) involved in protein translocation. It is at present unknown whether there can be genetic heterogeneity or not, as not all known families have been tested.
Diagnosis is based on the presence of characteristic clinical findings. X-rays of the hands and feet and a brain stem auditory evoked response (BAER) test for hearing loss should be performed. Molecular genetic testing identifying a ATP6V1B2 mutation may confirm the diagnosis but as it is at present uncertain whether DDOD syndrome is genetically heterogeneous, the absence of a mutation will not mean that a diagnosis of DDOD syndrome is incorrect.
The main differential diagnosis is DOORS syndrome and Coffin-Siris syndrome (see these terms). The limb anomalies seen in DDOD syndrome can also be found in several other entities including Zimmermann-Laband syndrome, Adams-Oliver syndrome, Temple-Baraitser syndrome and progeroid syndrome, Petty type (see these terms).
Prenatal diagnosis of DDOD syndrome has not been performed to date.
DDOD syndrome is inherited autosomal dominantly so if the clinical diagnosis has been established reliably, genetic counseling is possible.
Management and treatment
Treatment is supportive and involves special education for the hearing impaired as well as regular follow-up. Corrective surgery is in principle possible for those with syndactyly, although generally not necessary.
The disease is not life threatening. The main influence on quality of life is hearing loss.