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An Approach to Visual Loss in a Child
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Muhammad Hassaan Ali, Stacy L. Pineles
Retina dystrophies are a group of diseases which cause congenital retinal blindness. They generally present late in childhood and are common in developing countries where cousin marriages are highly prevalent. These diseases are usually managed with low vision aids that provide navigatory vision to the affected individual. LCA is a group of hereditary (mostly autosomal recessive) retinal dystrophies which produce severe visual impairment at a very early age (50). Affected children usually present with severely reduced vision, high hyperopia, sluggish or absent pupillary light reflexes and nystagmus which may be pendular to roving from very early age. The electroretinogram of these patients show markedly reduced scotopic and mesopic responses which are hallmark of this condition. The fundus may show no changes in the early stages to retinitis pigmentosa like bone spicule lesions in the late course of the disease. Oculodigital syndrome manifests with oculodigital phenomenon (constant rubbing of the eyes for retinal stimulation leading to enophthalmos), deafness, learning disabilities and epilepsy. Patients with Knobloch syndrome present with nystagmus, myopia and retinal detachment (51). Oculocutaneous albinism is usually X-linked or autosomal recessive (52). It presents with characteristic transillumination defects in iris and hypopigmented fundi and is usually associated with nystagmus. Achromatopsia is an autosomal recessive disease which produces color vision abnormalities and decreased central vision (53). Patients with achromatopsia present with photophobia and nystagmus in early childhood. The evaluation of children with retinal dystrophies is difficult as they often present early in infancy with poor vision but a relatively normal eye examination (Figure 21A.2).
Whole genome sequencing in a Knobloch syndrome family confirms the molecular diagnosis
Published in Ophthalmic Genetics, 2022
Chetan Khantibai Patel, Suzanne Broadgate, Ahmed Shalaby, Jing Yu, Andrea H. Nemeth, Susan M Downes, Stephanie Halford
Knobloch syndrome (KNO1, MIM #267750) is a rare autosomal recessive developmental disorder characterised by eye abnormalities and occipital skull defects. It was first described by Knobloch and Layer in 1971 in a family with 5 affected siblings who presented with high myopia, vitreoretinal degeneration, retinal detachment and congenital encephalocele (1). Since then, both the ocular and non-ocular phenotypes have expanded demonstrating clinical heterogeneity. The ocular features may also include early onset cataracts, lens subluxation, macular abnormalities, smooth irides and persistent fetal vasculature (2–6). The occipital defects can also range in severity from occipital encephalocele scalp defects to focal scalp alopecia with no underlying skull abnormalities (1,7–9). Additional brain malformations have also been reported and include polymicrogyria, intellectual disability and epilepsy (10–14). Lung and renal involvement has also been described (5). For a more detailed review of the phenotype, see the study by Heljasvaara et al. (15).
Three cases of molecularly confirmed Knobloch syndrome
Published in Ophthalmic Genetics, 2020
Irina Balikova, Nuri Serdal Sanak, Depasse Fanny, Guillaume Smits, Julie Soblet, Elfride de Baere, Monique Cordonnier
We present the clinical details of three molecularly proven patients with Knobloch syndrome. In all three patients, biallelic mutations have been identified within the COL18A1 gene. All mutations are novel and lead to frameshift.