Chorioretinopathy with Microcephaly 2

Clinical Characteristics
Ocular Features: 

Microphthalmia and microcornea are seen in most individuals and one patient had unilateral clinical anophthalmia. Hyperopia and cataracts may be present. Nystagmus is common.  One patient had a corneal opacity.  The chorioretinopathy has not been described beyond evidence of the maculopathy, attenuated retinal vessels, and occasionally hyperpigmented zones.  The ERG is either not recordable or consistent with a severe rod-cone dystrophy.  Vitreous inclusions and a 'vitreoretinal dystrophy' with falciform retinal folds were noted in several patients.  A traction detachment was present in one and bilateral serous detachments were noted in another.

Systemic Features: 

Patients have mild to severe microcephaly (up to -15 SD) with psychomotor delays.  Profound intellectual disability is a consistent feature.  Physical growth is retarded and patients have shortness of stature.  Most patients are unable to sit, stand, or walk unassisted.  One patient died at 5.5 years of age while another was alive at 20 years of age.  Rare patients may have hearing loss and seizures.

Scoliosis, kyphosis, and lordosis may be seen while  other skeletal malformations seem to occur sporadically e.g., triphalangeal thumbs, brachydactyly, postaxial polydactyly, and restricted large joint motion.  

The forehead slopes markedly.  Neuroimaging shows a consistent reduction in cortex size with simple gyral folding while the cerebellum and the brain stem are also small.  Subarachnoid cysts have been noted in several patients and the corpus callosum may be short or otherwise malformed.

Genetics

Homozygous mutations in the PLK4 gene (4q28.2) segregate with this condition.  Its product localizes to centrioles and plays a central role in centriole duplication.

For a somewhat similar condition but without the sloping forhead see Chorioretinoapathy with Microcephaly 1 (251270) but resulting from homozygous mutations in TUBGCP6.

Treatment
Treatment Options: 

No treatment is know.

References
Article Title: 

Mutations in PLK4, encoding a master regulator of centriole biogenesis, cause microcephaly, growth failure and retinopathy

Martin CA, Ahmad I, Klingseisen A, Hussain MS, Bicknell LS, Leitch A, Nurnberg G, Toliat MR, Murray JE, Hunt D, Khan F, Ali Z, Tinschert S, Ding J, Keith C, Harley ME, Heyn P, Muller R, Hoffmann I, Daire VC, Dollfus H, Dupuis L, Bashamboo A, McElreavey K, Kariminejad A, Mendoza-Londono R, Moore AT, Saggar A, Schlechter C, Weleber R, Thiele H, Altmuller J, Hohne W, Hurles ME, Noegel AA, Baig SM, Nurnberg P, Jackson AP. Mutations in PLK4, encoding a master regulator of centriole biogenesis, cause microcephaly, growth failure and retinopathy. Nat Genet. 2014 Dec;46(12):1283-92.

PubMed ID: 
25344692

References

Martin CA, Ahmad I, Klingseisen A, Hussain MS, Bicknell LS, Leitch A, Nurnberg G, Toliat MR, Murray JE, Hunt D, Khan F, Ali Z, Tinschert S, Ding J, Keith C, Harley ME, Heyn P, Muller R, Hoffmann I, Daire VC, Dollfus H, Dupuis L, Bashamboo A, McElreavey K, Kariminejad A, Mendoza-Londono R, Moore AT, Saggar A, Schlechter C, Weleber R, Thiele H, Altmuller J, Hohne W, Hurles ME, Noegel AA, Baig SM, Nurnberg P, Jackson AP. Mutations in PLK4, encoding a master regulator of centriole biogenesis, cause microcephaly, growth failure and retinopathy. Nat Genet. 2014 Dec;46(12):1283-92.

PubMedID: 25344692