This disorder is characterized by the skeletal abnormalities and short stature. This is also considered as one of the forms of dwarfism. The affected infants are born with the shortened arms and legs along with a short trunk. As these children become older additional complications can develop such as hearing and vision problems. This rare disorder is estimated to affect around 1 in every one million births.
Causes
This develops as the result of a mutation in the gene COL2A1 which is responsible for the production of a protein that develops the type II collagen. This type of collagen is found in the cartilage that is the flexible tissue making up most of the skeleton system during the initial development stage. The cartilage later develops as the bones except for the ones that protect the ends of the bones. The genetic mutation affects the assembly of type II collagen molecules and as the result; the proper bone development is prevented. Kniest Dysplasia is inherited in an autosomal dominant pattern where one copy of the defective gene can cause the disorder.
Symptoms
Individuals affected with the Kniest Dysplasia are unusually short stature, present short deformed limbs, short chest and a long trunk. One of the characteristic features of this condition includes the presence of holes in the cartilage that appears as ‘Swiss-cheese’ on an X-ray. Later they may develop the curvature of the spine and enlargement of the joints. The facial features include the abnormally flat face, protruding eyes, cleft palate, a low nasal bridge and the drooping of the eyelids (blepharoptosis). They can also exhibit impaired speech, nearsightedness (myopia), dislocated eye lenses, glaucoma, hearing loss and frequent ear infections. As the individual grows, they may have enlarged joints and contracted hips affecting movement.
Diagnosis
The diagnosis is based on the medical history, a physical examination and various tests. This can include the X-rays to determine the skeletal problems, MRI to produces images of the organs and structures of the body and a CT scan. The prenatal diagnosis is also possible with diagnostic tests such as amniocentesis and CVS to detect the genetic mutations. The sonogram at the second trimester can also help identify some of the skeletal abnormalities.
Treatment
As each case of this condition is different, so the treatment options also vary. The affected child may require the non-surgical or surgical intervention that treats the specific abnormality. When a variety of problems are presented such as joint stiffness, limb shortening and scoliosis, the child may require the treatment when still young. Children with the club foot or cleft palate may need surgical intervention. The non-surgical procedure includes the bracing and physical therapy. In the case of a slight hearing problem, the child will be monitored to ensure the condition does not become worse. As complications can develop as the child grows older, they need to be monitored to help identify irregular growth or developments.
References
http://www.chop.edu/conditions-diseases/kniest-dysplasia
https://ghr.nlm.nih.gov/condition/kniest-dysplasia#inheritance
