Autosomal dominant deafness-onychodystrophy syndrome

Other Names: Deafness and onychodystrophy, dominant form; Familial ectodermal dysplasia with sensori-neural deafness and other anomalies; DDOD; Autosomal dominant deafness-onychodystrophy syndrome; Robinson Miller Bensimon syndrome; Robinson-Miller-Bensimon syndrome; DDOD 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.

Epidemiology

The prevalence is unknown but it has been reported in 22 individuals from ten families to date.

Cause

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.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

DDOD syndrome is inherited autosomal dominantly so if the clinical diagnosis has been established reliably, genetic counseling is possible.

Signs and symptoms

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 , DDOD patients follow a normal development and have normal intelligence.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Severe sensorineural hearing impairment

30%-79% of people have these symptoms

• Absent toenail
• Oligodontia(Failure of development of more than six teeth)
• Triphalangeal thumb(Finger-like thumb)

5%-29% of people have these symptoms

• Abnormal facial shape(Unusual facial appearance)
• Absent fifth fingernail(Absent nail of fifth finger)
• Absent thumbnail
• Aplasia cutis congenita(Absence of part of skin at birth)
• Conical tooth(Cone shaped tooth)
• Dolichocephaly(Long, narrow head)
• High forehead
• Hypoplastic toenails(Underdeveloped toenails)
• Intellectual disability(Mental deficiency)
• Pes planus(Flat feet)
• Poor speech
• Seizure
• Selective tooth agenesis
• Short thumb(Short thumbs)
• Small, conical teeth(Small, cone shaped teeth)

Diagnosis

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.

Differential diagnosis 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).

Antenatal diagnosis Prenatal diagnosis of DDOD syndrome has not been performed to date.

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.

Prognosis

The disease is not life threatening. The main influence on quality of life is hearing loss.

NIH genetic and rare disease info

• NIH info on Autosomal dominant deafness-onychodystrophy syndrome

Autosomal dominant deafness-onychodystrophy syndrome is a rare disease.

Autosomal dominant deafness-onychodystrophy syndrome Resources
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