DOORS syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

DOORS syndrome is a disorder involving multiple abnormalities that are present from birth (congenital). "DOORS" is an abbreviation for the major features of the disorder including deafness; short or absent nails (onychodystrophy); short fingers and toes (osteodystrophy); developmental delay and intellectual disability (previously called mental retardation); and seizures. Some people with DOORS syndrome do not have all of these features.

Most people with DOORS syndrome have profound hearing loss caused by changes in the inner ears (sensorineural deafness). Developmental delay and intellectual disability are also often severe in this disorder.

The nail abnormalities affect both the hands and the feet in DOORS syndrome. Impaired growth of the bones at the tips of the fingers and toes (hypoplastic terminal phalanges) account for the short fingers and toes characteristic of this disorder. Some affected individuals also have an extra bone and joint in their thumbs, causing the thumbs to look more like the other fingers (triphalangeal thumbs).

The seizures that occur in people with DOORS syndrome usually start in infancy. The most common seizures in people with this condition are generalized tonic-clonic seizures (also known as grand mal seizures), which cause muscle rigidity, convulsions, and loss of consciousness. Affected individuals may also have other types of seizures, including partial seizures, which affect only one area of the brain and do not cause a loss of consciousness; absence seizures, which cause loss of consciousness for a short period that appears as a staring spell; or myoclonic seizures, which cause rapid, uncontrolled muscle jerks. In some affected individuals the seizures increase in frequency and become more severe and difficult to control, and a potentially life-threatening prolonged seizure (status epilepticus) can occur.

Other features that can occur in people with DOORS syndrome include an unusually small head size (microcephaly) and facial differences, most commonly a wide, bulbous nose. A narrow or high arched roof of the mouth (palate), broadening of the ridges in the upper and lower jaw that contain the sockets of the teeth (alveolar ridges), or shortening of the membrane between the floor of the mouth and the tongue (frenulum) have also been observed in some affected individuals. People with DOORS syndrome may also have dental abnormalities, structural abnormalities of the heart or urinary tract, and abnormally low levels of thyroid hormones (hypothyroidism). Most affected individuals also have higher-than-normal levels of a substance called 2-oxoglutaric acid in their urine; these levels can fluctuate between normal and elevated.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

DOORS syndrome can be caused by mutations in the TBC1D24 gene. This gene provides instructions for making a protein whose specific function in the cell is unclear. Studies suggest the protein may have several roles in cells. The TBC1D24 protein belongs to a group of proteins that are involved in the movement (transport) of vesicles, which are small sac-like structures that transport proteins and other materials within cells. Research suggests that the TBC1D24 protein may also help cells respond to oxidative stress. Oxidative stress occurs when unstable molecules called free radicals accumulate to levels that can damage or kill cells. Studies indicate that the TBC1D24 protein is active in a variety of organs and tissues; it is particularly active in the brain and likely plays an important role in normal brain development. The TBC1D24 protein is also active in specialized structures called stereocilia. In the inner ear, stereocilia project from certain cells called hair cells. The stereocilia bend in response to sound waves, which is critical for converting sound waves to nerve impulses.

TBC1D24 gene mutations that cause DOORS syndrome are thought to reduce or eliminate the function of the TBC1D24 protein, but the specific mechanism by which loss of TBC1D24 function leads to the signs and symptoms of DOORS syndrome is not well understood.

In about half of affected individuals, no TBC1D24 gene mutation has been identified. The cause of DOORS syndrome in these individuals is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

DOORS syndrome is a rare disorder; its prevalence is unknown. Approximately 50 affected individuals have been described in the medical literature.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal fingernail morphology · Very frequent (99-80%)

An abnormality of the fingernails.

Abnormal toenail morphology · Very frequent (99-80%)

An anomaly of the toenail.

Abnormality of finger · Very frequent (99-80%)

An anomaly of a finger.

Abnormality of toe · Very frequent (99-80%)

An anomaly of a toe.

Absent fingernail · Very frequent (99-80%)

Absence of a fingernail.

Anteverted nares · Very frequent (99-80%)

Anteriorly-facing nostrils viewed with the head in the Frankfurt horizontal and the eyes of the observer level with the eyes of the subject. This gives the appearance of an upturned nose (upturned nasal tip).

EEG abnormality · Very frequent (99-80%)

Abnormality observed by electroencephalogram (EEG), which is used to record of the brain's spontaneous electrical activity from multiple electrodes placed on the scalp.

Gingival overgrowth · Very frequent (99-80%)

Hyperplasia of the gingiva (that is, a thickening of the soft tissue overlying the alveolar ridge. The degree of thickening ranges from involvement of the interdental papillae alone to gingival overgrowth covering the entire tooth crown.

Other findings in the same source

From: Orphanet

Additional reported features include Global developmental delay (Very frequent (99-80%)); Long philtrum (Very frequent (99-80%)); Toenail dysplasia (Very frequent (99-80%)); Wide nasal base (Very frequent (99-80%)); Wide nasal bridge (Very frequent (99-80%)); Bilateral tonic-clonic seizure (Frequent (79-30%)); Bulbous nose (Frequent (79-30%)); Clinodactyly of the 5th finger (Frequent (79-30%)); Coarse facial features (Frequent (79-30%)); Downturned corners of mouth (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing DOORS syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for DOORS syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.