Anauxetic dysplasia

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Anauxetic dysplasia is a disorder characterized by extremely short stature (dwarfism) and other skeletal abnormalities, an unusually large range of joint movement (hypermobility), dental problems, and distinctive facial features. Mild intellectual disability can also occur in this disorder.

People with anauxetic dysplasia have dwarfism with unusually short limbs for their height (disproportionate short stature) beginning before birth. Dislocation of the bones at the top of the spine (atlantoaxial subluxation) can also occur in this disorder, and may cause pinching (compression) of the spinal cord. As a result, affected individuals may experience neurological symptoms including pain, tingling, numbness, coordination problems, weakness, and paralysis. In severe cases, the spinal cord compression may lead to paralysis of the muscles needed for breathing, which can be life-threatening during early childhood.

Other skeletal abnormalities in anauxetic dysplasia include a barrel-shaped chest and a rounded upper back that also curves to the side (kyphoscoliosis). Without surgical correction, the kyphoscoliosis can constrict the lungs and cause difficulty breathing. People with anauxetic dysplasia can also have an exaggerated curvature of the lower back (hyperlordosis), dislocation of the hips, and soles of the feet that are rounded outward (rocker-bottom feet).

Typical facial features in anauxetic dysplasia include closely spaced eyes (hypotelorism), a flat or sunken appearance of the middle of the face (midface hypoplasia), an unusually large tongue (macroglossia), and a protruding chin (prognathism). Affected individuals can also have fewer teeth than normal (hypodontia).

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Anauxetic dysplasia can be caused by mutations in the RMRP gene. Unlike many genes, the RMRP gene does not contain instructions for making a protein. Instead, a molecule called a noncoding RNA, a chemical cousin of DNA, is produced from the RMRP gene. Several proteins attach (bind) to this RNA molecule, forming an enzyme complex called mitochondrial RNA-processing endoribonuclease, or RNase MRP.

The RNase MRP enzyme is thought to be involved in several important functions in the cell, including processing ribosomal RNA. This form of RNA is associated with cell structures called ribosomes, which assemble protein building blocks (amino acids) into proteins.

The RMRP gene mutations that cause anauxetic dysplasia alter the noncoding RNA produced from the gene, and the RNase MRP enzyme containing the altered noncoding RNA is impaired in its ribosomal RNA processing function. Although the specific mechanism is unknown, impairment of this function likely disrupts skeletal development, leading to the signs and symptoms of anauxetic dysplasia.

Mutations in at least one gene that provides instructions for making a protein component of the RNase MRP enzyme complex can also cause anauxetic dysplasia.

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

Anauxetic dysplasia is a very rare disorder; its prevalence is unknown.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Disproportionate short stature

A kind of short stature in which different regions of the body are shortened to differing extents.

Mild intellectual disability

Mild intellectual disability (ID) is defined as a type of ID characterized by mildly sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 50-69.

Intellectual disability

The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence.

Barrel-shaped chest

A rounded, bulging chest that resembles the shape of a barrel. That is, there is an increased anteroposterior diameter and usually some degree of kyphosis.

Kyphoscoliosis

An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.

Which doctor should you see?

The suggested department for discussing Anauxetic dysplasia is Orthopaedics, with a orthopaedic specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

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.

• What explains the change in pain, movement or function?
• Which activities need adjustment while the diagnosis is being clarified?
• What are the roles of rehabilitation, observation and surgery in this situation?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Anauxetic dysplasia. 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.