Kniest Dysplasia

Clinical Characteristics
Ocular Features: 

High myopia and vitreoretinal degeneration are characteristic ocular features in this disorder.   The myopia is in the range of -7.5 to -15.25 with most patients having about -11 diopters.  Acuity may be normal but inoperable retinal detachments can lead to blindness.  The vitreous demonstrates liquefaction and syneresis and often detaches posteriorly forming a retrolental curtain.  About half of affected eyes have perivascular lattice degeneration and the same proportion of patients at some point develop a retinal detachment.  Giant tears and retinal dialysis are commonly the cause.  The lens is often dislocated and cataracts are common.

Systemic Features: 

Short stature, cleft palate, stiff joints, and conductive hearing loss are characteristic extraocular features of Kniest dysplasia.  Some patients develop frank joint contractures and many are unable to make a tight fist due to inflexibility of the interphalangeal joints.  Lumber kyphoscoliosis is common.  Epiphyseal cartilage has a 'Swiss cheese appearance' with prominent lacunae.  The facies are round and the midface is underdeveloped with a flat nasal bridge.  Mild psychomotor retardation is sometimes seen.  

High levels of keratin sulfate are found in the urine.

Genetics

Mutations in the COL2A1 gene (12q13.11-q13.2) coding for type II collagen is responsible for this autosomal dominant disorder. This is one of a number of disorders known as type II collagenopathies (see Stickler syndrome I [609508]).  The clinical features arise from a defect in type II procollagen.

Treatment
Treatment Options: 

There is no treatment for the dysplasia.  Displaced lenses can be removed but the myopia and degenerated vitreous require a cautious approach.  Rhegmatogenous detachments demand prompt attention.

References
Article Title: 

Ophthalmic and molecular genetic findings in Kniest dysplasia

Sergouniotis PI, Fincham GS, McNinch AM, Spickett C, Poulson AV, Richards AJ, Snead MP. Ophthalmic and molecular genetic findings in Kniest dysplasia. Eye (Lond). 2015 Jan 16. doi: 10.1038/eye.2014.334. [Epub ahead of print].

PubMed ID: 
25592122

The Kniest syndrome

Siggers CD, Rimoin DL, Dorst JP, Doty SB, Williams BR, Hollister DW, Silberberg R, Cranley RE, Kaufman RL, McKusick VA. The Kniest syndrome. Birth Defects Orig Artic Ser. 1974;10(9):193-208.

PubMed ID: 
4214536

References

Sergouniotis PI, Fincham GS, McNinch AM, Spickett C, Poulson AV, Richards AJ, Snead MP. Ophthalmic and molecular genetic findings in Kniest dysplasia. Eye (Lond). 2015 Jan 16. doi: 10.1038/eye.2014.334. [Epub ahead of print].

PubMedID: 25592122

Maumenee IH, Traboulsi EI. The ocular findings in Kniest dysplasia. Am J Ophthalmol. 1985 Jul 15;100(1):155-60.

PubMedID: 4014370

Siggers CD, Rimoin DL, Dorst JP, Doty SB, Williams BR, Hollister DW, Silberberg R, Cranley RE, Kaufman RL, McKusick VA. The Kniest syndrome. Birth Defects Orig Artic Ser. 1974;10(9):193-208.

PubMedID: 4214536