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Carrier Screening For Inherited Genetic Conditions
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Whitney Bender, Lorraine Dugoff
Clinical features: This syndrome is caused by abnormal glycosylation of alpha-dystroglycan. This abnormal protein causes progressive weakness of skeletal muscles and abnormal migration of neurons. Affected individuals have hypotonia and can never walk. Cobblestone lissencephaly results in development and intellectual disability. Microphthalmia is also common. Most individuals do not survive past age 3.
The eye
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
Microphthalmos and anophthalmos constitute an extremely heterogeneous group. Unilateral cases are frequently non-genetic but cannot be securely distinguished from genetic forms. Rubella, toxoplasmosis, maternal thalidomide and other drug exposures are possible causes of bilateral disease. Mental retardation is frequently associated, and microphthalmos is a feature of several chromosomal defects as well as Mendelian syndromes. The X-linked Lenz syndrome of microphthalmos with cataract, mental retardation and digital and genitourinary abnormalities must be considered. Microphthalmos with coloboma is usually autosomal dominant (in the absence of known external causes) and is heterogeneous. Complete bilateral anophthalmia can be difficult to distinguish from extreme microphthalmos and may result from environmental factors. Cryptophthalmos, with absent palpebral fissures, may be part of the previously mentioned disorders, or may occur with relatively normal eye development, usually following autosomal recessive inheritance. Some cases are part of the more general Fraser syndrome (autosomal recessive), where renal agenesis and laryngeal atresia may be major features, and where a specific developmental gene defect is known.
Hyperthermia and Teratogenicity
Published in Leopold J. Anghileri, Jacques Robert, Hyperthermia In Cancer Treatment, 2019
Fraser and Skelton69 studied case histories of 479 children with congenital malformations, cerebral palsy, mental retardation, or convulsive disorders. The presence or absence of febrile episodes during pregnancy had been recorded. In 36 cases, fever occurred during the first 5 months of gestation. Microphthalmia occurred significanly more often (p ⩽0.001) when fever was reported than when it was not. The authors concluded that the findings support the hypothesis that fever during pregnancy increases the probability of developmental disorders, particularly microphthalmia, in humans.
Clinical diagnosis of presumed SOX2 gonadosomatic mosaicism
Published in Ophthalmic Genetics, 2021
Malena Daich Varela, Robert B. Hufnagel, Bin Guan, Delphine Blain, Julie C. Sapp, Andrea L. Gropman, Ramakrishna Alur, Jennifer J. Johnston, Leslie G. Biesecker, Brian P. Brooks
Microphthalmia (OMIM #309700) is a developmental malformation in which the eyes are small (axial length <20 mm). It can appear simple (also called pure or primary, where the eye is otherwise structurally normal) or complex (where it is combined with other ocular abnormalities, most frequently microcornea and coloboma) (1). It has an estimated prevalence of 1 per 7,000 live births (2). Up to 80% of the individuals with microphthalmia have a syndromic form, associated with non-ocular malformations (3). Microphthalmia is considered part of a larger phenotypic continuum (i.e., the Microphthalmia-Anophthalmia-Coloboma (MAC) spectrum), where the mildest end is represented by forme fruste coloboma. The latter can appear as pigment loss in the inferior quadrant of the iris (sectoral transillumination defects), atypical optic disc cupping, and/or mild, flat choroidal lesions along the six o’clock meridian (4,5). The etiology of most cases of MAC remains unknown, although environmental (infection, nutritional deficiency or drug intake during the first trimester of the pregnancy) and genetic causes have been described (6). Among the last, pathogenic variants in the transcription factor gene SOX2 have been reported as causative in 10–20% of the individuals with anophthalmia or severe microphthalmia, and in up to 40% of those affected bilaterally (7,8).
Aplasia of the Optic Nerve: A Report of Seven Cases
Published in Neuro-Ophthalmology, 2020
Yujia Zhou, Maura E. Ryan, Marilyn B. Mets, Hawke H. Yoon, Bahram Rahmani, Sudhi P. Kurup
ONA is typically associated with other ocular abnormalities1 as seen here, too (Table 1). All of our patients clinically demonstrated microphthalmia and various involvements of both anterior and posterior segments in their affected eye(s) (n = 7, 100%). Microphthalmia usually indicates anatomic alterations of the eye and is a feature of many ocular diseases.12 In Case 4, no pathogenic variant was detected in four genes known to cause microphthalmia, indicating that other genes, epigenetic, or environmental factors may be contributory.6 It has been suggested that ONA may be underdiagnosed in the setting of severe microphthalmia due to difficulties of examining the eyes via funduscopy.13 Anomalous retina, as seen in all of our patients (n = 7, 100%), is another prominent feature of ONA, which indicates a close relationship between the optic nerve and retinal development. Neovascularization of the posterior segment has been reported, which was attributed to retinal ischaemia.14 In contrast, the neovascularization of our patients occurred in the anterior segment (n = 2, 29%). Other common ocular features in our patients included persistent pupillary membrane (n = 4, 57%), coloboma (n = 3, 43%), cataract (n = 3, 43%), posterior synechiae (n = 3, 43%), corneal abnormalities (n = 2, 29%), and elevated IOP (n = 2, 29%).
Anophthalmia and microphthalmia in children: associated ocular, somatic and genetic morbidities and quality of life
Published in Ophthalmic Genetics, 2022
Cecilia Fahnehjelm, Eva Dafgård Kopp, Josephine Wincent, Evin Güven, Mattias Nilsson, Monica Olsson, Kristina Teär Fahnehjelm
Clinical guidelines for the diagnosis and treatment of patients with anophthalmia or microphthalmia adapted from Ragge et al. (16) Suspicion of microphthalmia if the horizontal corneal diameter is <9 mm in neonatesDiagnosis of microphthalmia, if the axial length of the bulb is <15.8 mm on ultrasound or MRI in a neonateRefer to a paediatric ophthalmologistRefer to oculoplastics and prosthetics unit if bulb length is <16 mm neonatally.MRI of the brain and orbits to detect pathology and measure axial lengthVEP in selected cases, but the results should be interpreted with cautionMultidisciplinary approaches including paediatricians and ear, nose and throat specialists.Long-term follow-up is needed as associated comorbidities in the other eye or other organs and psychomotor delay or behavioural problems may not be evident in the neonatal periodGenetic evaluation is strongly recommended both in children born with unilateral or bilateral microphthalmia/anophthalmia