Kniest dysplasia
A rare dwarfism caused by COL2A1 mutation, first described in 1952.
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Kniest dysplasia is a rare form of dwarfism caused by a mutation in the COL2A1 gene on chromosome 12, which is responsible for producing type II collagen. It is characterized by abnormal skeletal growth, hearing and vision problems, and is distinguished from other type II osteochondrodysplasias by its severity and the dumb-bell shape of shortened long tubular bones. The condition was first described by Dr. Wilhelm Kniest in 1952.
Quick Facts
- First described
- 1952
- Described by
- Dr. Wilhelm Kniest
- Gene involved
- COL2A1
- Chromosome
- 12
- Inheritance
- Autosomal dominant
- Prevalence
- Less than 1 in 1,000,000 people
- Alternative names
- Kniest syndrome
- swiss cheese cartilage syndrome
- Kniest chondrodystrophy
- metatrophic dwarfism type II
Facts from the source article.
Signs and symptoms
Because collagen is important for body development, symptoms of Kniest dysplasia typically appear at birth. Musculoskeletal problems include short limbs, a shortened body trunk, flattened spinal bones (platyspondyly), kyphoscoliosis, scoliosis, and early arthritis. Respiratory issues such as infections and difficulty breathing may occur.
Eye problems include severe myopia, cataracts, and a predisposition to retinal detachment due to cranial structure elongating the eyeball. Hearing problems involve progressive hearing loss and ear infections. Most symptoms are chronic and worsen with age, requiring regular checkups with various specialists.
Diagnosis
Kniest dysplasia is an autosomal dominant condition, meaning one copy of the mutated gene is sufficient for the disorder. A family history increases risk, but a random mutation can also cause it.
Diagnosis uses a combination of imaging tests: CT scans, MRI, EOS imaging (which shows weight-bearing posture), and X-rays to detect bone anomalies. Key features on imaging include dumb-bell shaped femur bones and coronal clefts in the vertebrae, along with platyspondyly, kyphoscoliosis, abnormal growth of epiphyses, metaphyses, and diaphysis, short tubular bones, and narrowed joint spaces. Genetic testing of the COL2A1 gene can confirm the condition as a type II chondrodysplasia.
Treatment
Treatment varies based on the body systems affected and may be non-surgical or surgical. Options include spinal fusion for severe kyphoscoliosis, extension osteotomy for progressive joint limitation, surgical realignment, retinal detachment repair, and myringotomy to drain fluid from the eardrum. Routine monitoring, oxygen support (CPAP, bipap, mechanical ventilation), physical therapy, and bracing are also used. Prognosis depends on symptom severity, but most individuals have normal intelligence and can lead a normal life.
Did You Know?
- Analysis of the original patient's DNA in 1992 revealed a deletion of a 28 base pair sequence encompassing a splice site in exon 12 and a G to A transition in exon 50 of the COL2A1 gene.
- Males and females have equal chances of having Kniest dysplasia.
More in Skeletal Disorders
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Kniest dysplasia (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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