Platyspondylic dysplasia, Torrance type

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Platyspondylic dysplasia, Torrance type is a severe disorder of bone growth. Infants with this condition have very short arms and legs, severely flattened bones of the spine (platyspondyly), and unusually short fingers and toes (brachydactyly). Affected individuals also tend to have a small chest with short ribs that can restrict the growth and expansion of the lungs.

The serious health problems seen in infants with platyspondylic dysplasia, Torrance type often result in death before birth or shortly thereafter; respiratory failure is a common cause of death.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Platyspondylic dysplasia, Torrance type is caused by variants (also called mutations) in the COL2A1 gene. This gene provides instructions for making the alpha-1(II) chain, which is a component of type II collagen. This type of collagen is found in the clear gel that fills the eyeball (the vitreous) and in cartilage. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development; most cartilage is later converted to bone. Type II collagen is essential for the normal growth and development of bones and other connective tissues.

Most of the COL2A1 variants that cause platyspondylic dysplasia, Torrance type affect a region of the protein called the C-propeptide domain. These variants cause the cell to produce an abnormal version of the COL2A1 protein, which interferes with the formation of mature type II collagen molecules. In some cases, the abnormal alpha-1(II) chains build up in cartilage-forming cells (chondrocytes). Without enough functioning type II collagen, bones and other connective tissues cannot develop properly, leading to the skeletal abnormalities seen in infants with platyspondylic dysplasia, Torrance type.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. This condition is usually the result of a new (de novo) variant in the gene that occurs during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development. These affected individuals typically have no history of the disorder in their family. However, in some cases, a parent has been found to carry the same variant in a small number of their cells, which is known as somatic mosaicism.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Platyspondylic dysplasia, Torrance type is very rare, though the exact prevalence 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.

Abdominal distention · Very frequent (99-80%)

Distention of the abdomen.

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

An abnormality affecting the carpal bones of the wrist (scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, hamate).

Bowing of the long bones · Very frequent (99-80%)

A bending or abnormal curvature of a long bone.

Disproportionate short-limb short stature · Very frequent (99-80%)

A type of disproportionate short stature characterized by a short limbs but an average-sized trunk.

Hypoplasia of the capital femoral epiphysis · Very frequent (99-80%)

Underdevelopment of the proximal epiphysis of the femur.

Hypoplastic pelvis · Very frequent (99-80%)

Underdevelopment of the bony pelvis.

Metaphyseal cupping · Very frequent (99-80%)

Metaphyseal cupping refers to an inward bulging of the metaphyseal profile giving the metaphysis a cup-like appearance.

Micromelia · Very frequent (99-80%)

The presence of abnormally small extremities.

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.

Platyspondyly · Very frequent (99-80%)

A flattened vertebral body shape with reduced distance between the vertebral endplates.

Short distal phalanx of finger · Very frequent (99-80%)

Short distance from the end of the finger to the most distal interphalangeal crease or the distal interphalangeal joint flexion point. That is, hypoplasia of one or more of the distal phalanx of finger.

Short foot · Very frequent (99-80%)

A measured foot length that is more than 2 SD below the mean for a newborn of 27 - 41 weeks gestation, or foot that is less than the 3rd centile for individuals from birth to 16 years of age (objective). Alternatively, a foot that appears disproportionately short (subjective).

Short palm · Very frequent (99-80%)

Short palm.

Short thorax · Very frequent (99-80%)

Reduced inferior to superior extent of the thorax.

Other findings in the same source

From: Orphanet

Additional reported features include Skeletal dysplasia (Very frequent (99-80%)); Depressed nasal bridge (Frequent (79-30%)); Genu varum (Frequent (79-30%)); Hydrops fetalis (Frequent (79-30%)); Hypoplastic scapulae (Frequent (79-30%)); Low-set ears (Frequent (79-30%)); Malar flattening (Frequent (79-30%)); Polyhydramnios (Frequent (79-30%)); Prominent forehead (Frequent (79-30%)); Pulmonary hypoplasia (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 Platyspondylic dysplasia, Torrance type 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 Platyspondylic dysplasia, Torrance type. 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.