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Disorders of pigmentation
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
Mutation in the TYR gene, P gene, TYRP1 gene, and MATP gene leads to OCA-1,2,3 and 4, respectively. Ocular albinism is a distinct variant wherein only ocular symptoms are present without any cutaneous lesions.
The skin
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
Ocular albinism (see Chapter 19) is X-linked, the gene being mapped to distal Xp. There are other X-linked disorders of the eye that can also lead to nystagmus and reduced pigmentation within the eye, such as Åland Island eye disease, and practitioners should be aware of these distinctions.
Oculocutaneous albinism
Published in Electra Nicolaidou, Clio Dessinioti, Andreas D. Katsambas, Hypopigmentation, 2019
Mira Kadurina, Anastasiya A. Chokoeva, Torello Lotti
Ocular albinism is associated with mutations in the GPR143 gene, resulting in dysfunctional melanosome biogenesis with “macromelanosomes.” The pigment dysfunction is limited to the eyes, and the ocular problems are severe, including nystagmus, foveal hypoplasia, and photophobia with impaired visual acuity. Pale skin may be seen in addition. Almost all of the female carriers show X-inactivation with pigmentary mosaicism in the retina, which is an important diagnostic clue for affected male children.5,8,9
GPR143 genotypic and ocular phenotypic characterisation in a Chinese cohort with ocular albinism
Published in Ophthalmic Genetics, 2021
Junwei Zhong, Bing You, Ke Xu, Xiaohui Zhang, Yue Xie, Yang Li
In this cohort, all patients presented with nystagmus, decreased BCVA, and severe foveal hypoplasia, which are three prominent clinical features commonly detected in Chinese patients with OA1 (13–15). We did not find any solid correlation between the genotype and phenotype, in agreement with previous results reported in Caucasian patients (9). Our patients’ ERG recordings all showed normal rod function and a mild to moderate reduction in photopic responses. We did not record any of the “exaggerated” normal responses described in a very early study (20). In that study, Krill and Lee reported that ERG recordings taken from the patients with oculocutaneous or ocular albinism showed larger amplitudes and shorter implicit times when compared with recordings from normal controls (20). They proposed that the supernormal amplitude of the ERG was due to an increased intraocular scatter of light, which resulted from a decreased absorption of stray light by the hypomelanotic RPE and choroid (20). In a subsequent study, Wack et al. found that only the ERG recordings obtained from oculocutaneous albinism eyes showed amplitudes larger than the upper limit of normal eyes or implicit times shorter than the lower limit of normal eyes (21). They hypothesized that these changes likely reflected the increased amount of stimulating light crossing the eye through a hypopigmented anterior segment (21). By contrast, Tomei and Wirth reported that the ERG results from a group of patients with ocular albinism were either normal or subnormal in amplitude (22).
Clinical albinism score, presence of nystagmus and optic nerves defects are correlated with visual outcome in patients with oculocutaneous albinism
Published in Ophthalmic Genetics, 2021
Alina V. Dumitrescu, Johnny Tran, Wanda Pfeifer, Sajag V. Bhattarai, Andrew Kemerley, Taylor V. Dunn, Kai Wang, Tod E. Scheetz, Arlene Drack
Oculocutaneous albinism (OCA) represents a heterogeneous group of disorders that affect melanin production. Melanin is required for pigmentation of the skin and hair as well as for proper development of the visual system, and defects in the pathway required for melanin synthesis can lead to OCA(1). The disorder has been referred to as ocular albinism (OA) when decreased pigmentation appears to be restricted to the eye; however, this is a misnomer since patients with “ocular albinism” have abnormal macro-melanosomes on skin biopsy (2,3). Besides, mutations in a recently discovered albinism-like gene, SLC38A8, result in normal skin pigmentation with ocular findings of albinism (4,5). In some syndromic forms of albinism, like Hermansky-Pudlak syndrome (HPS), melanosome biogenesis is primarily affected as well as maturation and secretion of lysosome-related organelles (6). Albinism often causes lifelong visual impairment, although the range of visual acuities is wide from legal blindness to only a minimal decrease in vision. The prevalence is estimated to be around 1/20,000 worldwide and affects people of all races and ethnicities (7). It is more common in parts of Africa, such as Zimbabwe, where the prevalence is estimated to be 1:4000 (8).
Ocular findings of albinism in DYRK1A-related intellectual disability syndrome
Published in Ophthalmic Genetics, 2020
Julia Ernst, Michelle L. Alabek, Amgad Eldib, Suneeta Madan-Khetarpal, Jessica Sebastian, Aashim Bhatia, Alkiviades Liasis, Ken K. Nischal
In summary, our patient’s systemic features are consistent with DYRK1A-related intellectual disability syndrome. To our knowledge, a VEP pattern suggestive of ocular findings of albinism has not previously been reported in this disorder. Given that no other molecular explanation for her ocular albinism features was identified by exome sequencing, we propose that our patient manifests previously unreported ocular findings of albinism that are associated with DYRK1A haploinsufficiency. Since her ocular features of albinism are mild and the advent of VEP testing is not readily available at all institutions, it is possible that this is an unrecognized feature of DYRK1A-related disease. Moreover, the absence of nystagmus may seem contradictory to a diagnosis of ocular albinism, but there are several reports of ocular albinism in the absence of clinically obvious nystagmus (14,17,18). We suggest that patients with a DYRK1A haploinsufficiency should be evaluated for signs of ocular albinism. Such evaluations should include measurement of baseline VEPs and screening for retinal hypopigmentation with iris transillumination.