Atelosteogenesis type 2

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Atelosteogenesis type 2 is a severe disorder of cartilage and bone development. Infants born with this condition have very short arms and legs, a narrow chest, and a prominent, rounded abdomen. This disorder is also characterized by an opening in the roof of the mouth (a cleft palate), distinctive facial features, an inward- and upward-turning foot (clubfoot), and unusually positioned thumbs (hitchhiker thumbs).

The signs and symptoms of atelosteogenesis type 2 are similar to those of another skeletal disorder called diastrophic dysplasia; however, atelosteogenesis type 2 is typically more severe. As a result of serious health problems, infants with this disorder are usually stillborn or die soon after birth from respiratory failure. Some infants, however, have lived for a short time with intensive medical support.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Atelosteogenesis type 2 is one of several skeletal disorders caused by mutations in the SLC26A2 gene. This gene provides instructions for making a protein that is essential for the normal development of cartilage and for its conversion to bone. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, except for the cartilage that continues to cover and protect the ends of bones and is present in the nose and external ears. Mutations in the SLC26A2 gene disrupt the structure of developing cartilage, preventing bones from forming properly and resulting in the skeletal problems characteristic of atelosteogenesis type 2.

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

Atelosteogenesis type 2 is an extremely rare genetic disorder; its incidence is unknown.

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.

Limb undergrowth · Very frequent (99-80%)

Limb shortening because of underdevelopment of one or more bones of the extremities.

Abnormal facial shape · Frequent (79-30%)

An abnormal morphology (form) of the face or its components.

Bell-shaped thorax · Frequent (79-30%)

The rib cage has the shape of a wide mouthed bell. That is, the superior portion of the rib cage is constricted, followed by a convex region, and the inferior portion of the rib cage expands again to have a large diameter.

Bilateral talipes equinovarus · Frequent (79-30%)

Bilateral clubfoot deformity.

Brachydactyly · Frequent (79-30%)

Digits that appear disproportionately short compared to the hand/foot. The word brachydactyly is used here to describe a series distinct patterns of shortened digits (brachydactyly types A-E). This is the sense used here.

Broad metacarpals · Frequent (79-30%)

Abnormally broad metacarpal bones.

Broad phalanx · Frequent (79-30%)

Increased side-to-side width of one or more phalanges of the fingers or toes.

Camptodactyly · Frequent (79-30%)

The distal interphalangeal joint and/or the proximal interphalangeal joint of the fingers or toes cannot be extended to 180 degrees by either active or passive extension.

Cleft palate · Frequent (79-30%)

Cleft palate is a developmental defect of the palate resulting from a failure of fusion of the palatine processes and manifesting as a separation of the roof of the mouth (soft and hard palate).

Dumbbell-shaped femur · Frequent (79-30%)

The femur is shortened and displays flaring (widening) of the metaphyses.

Excessive femoral anteversion · Frequent (79-30%)

An increased degree of femoral version, which is defined as the angular difference between axis of femoral neck and transcondylar axis of the knee. Thus, femoral anteversion is an inward twisting of the femur that causes the knees and feet to turn inward.

Genu valgum · Frequent (79-30%)

The legs angle inward, such that the knees are close together and the ankles far apart.

Hitchhiker thumb · Frequent (79-30%)

With the hand relaxed and the thumb in the plane of the palm, the axis of the thumb forms an angle of at least 90 degrees with the long axis of the hand.

Laryngeal cartilage malformation · Frequent (79-30%)

A malformation of the laryngeal cartilage.

Other findings in the same source

From: Orphanet

Additional reported features include Laryngeal stenosis (Frequent (79-30%)); Metatarsus adductus (Frequent (79-30%)); Narrow chest (Frequent (79-30%)); Rhizomelia (Frequent (79-30%)); Rhizomelic arm shortening (Frequent (79-30%)); Sandal gap (Frequent (79-30%)); Short femur (Frequent (79-30%)); Short lower limbs (Frequent (79-30%)); Short metacarpal (Frequent (79-30%)); Short neck (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 Atelosteogenesis type 2 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 Atelosteogenesis type 2. 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.