Fibrochondrogenesis

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Fibrochondrogenesis is a very severe disorder of bone growth. Affected infants have a very narrow chest, which prevents the lungs from developing normally. Most infants with this condition are stillborn or die shortly after birth from respiratory failure. However, some affected individuals have lived into childhood.

Fibrochondrogenesis is characterized by short stature (dwarfism) and other skeletal abnormalities. Affected individuals have shortened long bones in the arms and legs that are unusually wide at the ends (described as dumbbell-shaped). People with this condition also have a narrow chest with short, wide ribs and a round and prominent abdomen. The bones of the spine (vertebrae) are flattened (platyspondyly) and have a characteristic pinched or pear shape that is noticeable on x-rays. Other skeletal abnormalities associated with fibrochondrogenesis include abnormal curvature of the spine and underdeveloped hip (pelvic) bones.

People with fibrochondrogenesis also have distinctive facial features. These include prominent eyes, low-set ears, a small mouth with a long upper lip, and a small chin (micrognathia). Affected individuals have a relatively flat-appearing midface, particularly a small nose with a flat nasal bridge and nostrils that open to the front rather than downward (anteverted nares). Vision problems, including severe nearsightedness (high myopia) and clouding of the lens of the eye (cataract), are common in those who survive infancy. Most affected individuals also have sensorineural hearing loss, which is caused by abnormalities of the inner ear.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Fibrochondrogenesis can result from mutations in the COL11A1 or COL11A2 gene. When the condition is caused by COL11A1 gene mutations, it is designated as type 1; when it is caused by COL11A2 gene mutations, it is designated as type 2. Both of these genes provide instructions for making components of type XI collagen, which is a complex molecule that gives structure and strength to the connective tissues that support the body's joints and organs. Specifically, type XI collagen is found in cartilage, a tough but 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. Type XI collagen is also part of the inner ear; the vitreous, which is the clear gel that fills the eyeball; and the nucleus pulposus, which is the center portion of the discs between vertebrae.

Mutations in the COL11A1 or COL11A2 gene impair the assembly of type XI collagen, in most cases leading to the production of abnormal collagen molecules. The defective collagen weakens connective tissues, impairing the formation of bones throughout the skeleton and causing changes in the eye and inner ear that lead to vision and hearing problems.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Fibrochondrogenesis is generally 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 usually do not show signs and symptoms of the condition. In a few reported cases, parents of children with fibrochondrogenesis have had mild features that may be related to the condition, including slightly short stature, myopia, cataracts, joint pain, and hearing loss.

In at least one case of fibrochondrogenesis caused by a COL11A2 gene mutation, the condition was inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In this case, the condition resulted from a new (de novo) mutation in the gene that occurred during the formation of reproductive cells (eggs or sperm) in one of the affected individual's parents. There was no history of the disorder in the family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Fibrochondrogenesis appears to be a rare disorder. About 20 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 diaphysis morphology · Very frequent (99-80%)

An abnormality of the structure or form of the diaphysis, i.e., of the main or mid-section (shaft) of a long bone.

Abnormal form of the vertebral bodies · Very frequent (99-80%)

Abnormal form of vertebral body, which is the central cylindrical portion of the vertebra that together with other structures such as the vertebral arch, pedicles, laminae, spinous process, transverse processes, and articular facets makes up a vertebra.

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

An abnormality of one or more metaphysis, i.e., of the somewhat wider portion of a long bone that is adjacent to the epiphyseal growth plate and grows during childhood.

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

An anomaly of the rib.

Bell-shaped thorax · Very frequent (99-80%)

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.

Brachydactyly · Very frequent (99-80%)

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 ribs · Very frequent (99-80%)

Increased width of ribs

Narrow chest · Very frequent (99-80%)

Reduced width of the chest from side to side, associated with a reduced distance from the sternal notch to the tip of the shoulder.

Other findings in the same source

From: Orphanet

Additional reported features include Proptosis (Very frequent (99-80%)); Round face (Very frequent (99-80%)); Short neck (Very frequent (99-80%)); Short ribs (Very frequent (99-80%)); Short stature (Very frequent (99-80%)); Wide anterior fontanel (Very frequent (99-80%)); Anteverted nares (Frequent (79-30%)); Cleft palate (Frequent (79-30%)); Depressed nasal bridge (Frequent (79-30%)); Downslanted palpebral fissures (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 Fibrochondrogenesis 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 Fibrochondrogenesis. 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.

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.