Chediak−Higashi Syndrome
Dongyou Liu in Handbook of Tumor Syndromes, 2020
Children with classic CHS tend to display: (i) partial oculocutaneous albinism (OCA, pigment dilution in hair, skin, and eyes, results in silvery or metallic hair [observable under the light microscope], reduced skin, iris, and retinal pigmentation, photophobia, and nystagmus); (ii) immunodeficiency (frequent/severe infections of the skin, upper respiratory tract, and periodontal region); (iii) immunodeficiency (recurrent infections); (iv) bleeding tendency (epistaxis, gum/mucosal bleeding, and easy bruising); (v) HLH (or accelerated phase; manifesting as fever, hepatosplenomegaly, lymphadenopathy, neutropenia, anemia, and sometimes thrombocytopenia, in addition to diffuse lymphohistiocytic infiltration of the liver, spleen, bone marrow, lymph nodes, and central nervous system; possibly triggered by Epstein−Barr virus infection and absence of NK cell function); (vi) neurologic features (low cognitive abilities, balance abnormalities, stroke, coma, ataxia, tremor, absent deep-tendon reflexes, and motor and sensory neuropathies) (Figure 65.1) [1,13–22].
Principles of Clinical Diagnosis
Susan Bayliss Mallory, Alanna Bree, Peggy Chern in Illustrated Manual of Pediatric Dermatology, 2005
General Albinism includes a group of genetic disorders with dilution or absence of ocular and cutaneous pigmentationAll races affectedLack of pigment is caused by an abnormal maturation of melanosomesTypes of oculocutaneous albinism (OCA):OCA 1A (tyrosinase-negative OCA)Marked hypopigmentation of the skin and eyes (Figure 14.26)Skin varies from pink to milky whiteHair whiteEyes are pale blue with a pink or red reflex which can be seen through the irisSevere photophobia caused by lack of pigmentAssociated ocular abnormalities: decreased visual acuity, nystagmus and strabismusOCA 1B (minimal pigment OCA, yellow OCA)
Oculocutaneous albinism
Electra Nicolaidou, Clio Dessinioti, Andreas D. Katsambas in Hypopigmentation, 2019
Albinism represents a large family of inherited disorders, characterized by enzyme defects, leading to impaired melanin production with decreased or absent melanin in the skin, hair, and eyes, resulting in hypo- or depigmentation, depending on the degree of lack of tyrosinase.1,2 The name of the disease comes from the Latin “albus,” meaning “white,” to emphasize the hallmark of its clinical manifestation. In contrast to vitiligo, the number of melanocytes in the skin is normal. This rare genetic condition can clinically present affecting the pigmentation of the eyes only or the eyes as well as the skin and hair, resulting in ocular (OA) or oculocutaneous albinism (OCA), respectively.3 To date, seven types of nonsyndromic albinism have been described, and oculocutaneous albinism is the most commonly presented form.1 Oculocutaneous albinism is caused by a mutation in specific genes that inhibit melanin biosynthesis within melanocytes. The deficiency of melanin pigment causes the clinical presentations of albinism.
A novel iris transillumination grading scale allowing flexible assessment with quantitative image analysis and visual matching
Published in Ophthalmic Genetics, 2018
Chen Wang, Flavia Brancusi, Zaheer M. Valivullah, Michael G. Anderson, Denise Cunningham, Adam Hedberg-Buenz, Bradley Power, Dimitre Simeonov, William A. Gahl, Wadih M. Zein, David R. Adams, Brian Brooks
Albinism is caused by a group of genetic disorders associated with reduced melanin pigment biosynthesis. Oculocutaneous albinism (OCA) results in decreased pigmentation in the hair, skin, and eyes. Most OCA is autosomal recessive and caused by one of four genes: TYR (OCA-1A and OCA-1B, MIM 203100), OCA2 (OCA-2, MIM 203200), TYRP1 (OCA-3, MIM 203290), and SLC45A2 (OCA-4, MIM 606574). Additional rare OCA genes have recently been reported.1–3 A separate group of rare conditions combine OCA-like albinism and involvement of nonpigmented tissues. Examples include the Hermansky–Pudlak syndrome (types 1–9) and Chediak–Higashi syndrome. Ocular albinism (GPR143, MIM 300500) is characterized by X-linked inheritance and hypopigmentation restricted principally to the eye. All types of OCA, as well as OA, are associated with variable nystagmus, foveal hypoplasia, retinal hypopigmentation, abnormal retinal axonal fiber decussation, and iris hypopigmentation. OCA has a substantial breadth of phenotypic heterogeneity confounding subtype diagnosis through phenotype evaluation alone.4 To date, treatment of albinism is largely supportive, including low-vision aids, correction of refractive errors, treatment of amblyopia, and extraocular muscle surgery for strabismus and/or anomalous head posture.
The challenges faced by clinicians diagnosing and treating infantile nystagmus Part I: diagnosis
Published in Expert Review of Ophthalmology, 2021
Eleni Papageorgiou, Irene Gottlob
Albinism has been traditionally divided into oculocutaneous albinism (OCA) or ocular albinism (OA) on the basis of phenotypical features. However, the recent advances in molecular genetics have expanded the classification of various albinism subtypes based on the genetic profile of patients. Oculocutaneous albinism (OCA) is characterized by disruption of melanin biosynthesis, resulting in a lack of pigmentation in the eyes, skin, and hair [80]. Oculocutaneous albinism is a group of autosomal recessive disorders which are classified into seven types according to the affected gene [81]. OCA1 is caused by mutations in the tyrosinase gene (TYR) and is present in most populations except African-Americans [81]. It can present with either a complete lack of melanin production (OCA1A) or partial melanin production (OCA1B). Mutations in OCA2, TYRP1, SLC45A2, SLC24A5, and LRMDA have been attributed to subtypes OCA2, OCA3, OCA4, OCA6, and OCA7, respectively [81]. OCA2 and OCA3 are more common in African populations and are milder forms of albinism. OCA4 is another mild form of albinism that has been recently found in Turkish, Japanese, German, and Korean patients [81]. For OCA6 and OCA7 there are only case reports in a Chinese family and a consanguineous Faroese family. OCA5 is very rare, and has been only mentioned in a case report of a Pakistani family. The OCA5 locus is at 4q24, but the causative gene has not yet been identified [82].
Nystagmus associated with macular dysplasia
Published in Strabismus, 2020
Fu-Bin Wang
Patients with oculocutaneous albinism mainly showed macular dysplasia, abnormal foveal depression, and increased foveal thickness with persistence of an inner nuclear layer, an inner plexiform layer, a ganglion cell layer, and a nerve fiber layer on SD-OCT. It was revealed that fundus was lack of pigment in retinal pigment epithelium with visible large choroidal vessels (Figure 1). Congenital aniridia showed a planar fovea in the macula with the lack of a foveal pit with nystagmus (Figure 2). The OCT section showed the absence of normal foveal pit in foveal hypoplasia (Figure 3). For monocular macular heterotopias, no nystagmus was detected with naked eyes (Figure 4). Nystagmus was not found in patients with congenital macular coloboma and congenital retinoschisis. SD-OCT images showed a macular coloboma in the right eye and macular epiretinal membrane was seen in the left eye and no other abnormalities were observed (Figure 5). SD-OCT images showed the congenital retinoschisis in both eyes (Figure 6).
Related Knowledge Centers
- Albinism
- Biosynthesis
- Eye
- Mutation
- Skin
- Melanin
- Melanocyte
- Hair
- Gene
- Dominance