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 [1] 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 [2] [609508 [3]]). 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 [4]

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 ocular findings in Kniest dysplasia [5]

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

PubMed ID:

4014370

The Kniest syndrome [6]

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