Knobloch Syndrome 3

Clinical Characteristics
Ocular Features: 

High myopia and marked nystagmus are cardinal ocular findings.  Night blindness leads to symptoms between 2 and 4 years of age.  Vision loss leads to complete blindness by age 15 to 18.  Visual acuity in young adults is often 20/400 to NLP.  Cataracts with subluxated lenses, glaucoma, and chorioretinal atrophy are often present.  Scattered pigment clumping, attenuation of the retinal vasculature, and prominent choroidal vessels can often be seen.  Marked optic atrophy is usually present.  Phthisis and band keratopathy may be seen in older individuals although no retinal detachments have been reported.  The vitreous is described as degenerated in several patients and a vitreal hemorrhage was seen in one patient.

Systemic Features: 

This variant was identified in a four-generation consanguineous Pakistani family in which detailed information was obtained in 5 members. A hairless, purplish-red patch is usually present in the occipital-parietal region during infancy but becomes smaller as children grow.  No encephalocele is present.  Hearing loss and heart defects have not been reported.  Intelligence is normal.

Genetics

This is an autosomal recessive condition resulting from a presumed homozygous mutation on chromosome 17 (17q11.2).

Other variants of Knobloch syndrome are Knobloch 1 (267750) caused by homozygous mutations in COL18A1 (21q22.3) and Knobloch 2 (608454) secondary to homozygous mutations in ADAMTS18 at 16q23.1.

Treatment
Treatment Options: 

Cataracts and dislocated lenses may be removed.

References
Article Title: 

References

Khaliq S, Abid A, White DR, Johnson CA, Ismail M, Khan A, Ayub Q, Sultana S, Maher ER, Mehdi SQ. Mapping of a novel type III variant of Knobloch syndrome (KNO3) to chromosome 17q11.2. Am J Med Genet A. 2007 Dec 1;143A(23):2768-74.

PubMedID: 17975799