Albinism is a rare genetic condition associated with a variable hypopigmentation phenotype, which can affect the pigmentation of only the eyes or both the eyes and the skin/hair, resulting in ocular (OA) or oculocutaneous albinism (OCA), respectively. At least four forms of OCA and one of OA are known, associated with TYR (OCA1), OCA2 (OCA2), TYRP1 (OCA3), SLC45A2 (OCA4) and GPR143 (OA1) loci, respectively. Additionally, the rarest syndromic forms of albinism, affecting the normal function of other organs, can be grouped in Hermansky–Pudlak syndrome (HPS1–9) and the Chediak–Higashi syndrome (CHS1). In summary, a total of 15 genes are currently associated with various types of albinism. However, new genes have been recently described, associated with autosomal recessive oculocutaneous albinism with highly similar phenotypes but diverse molecular origin, indicating that there are likely to be more than 15 genes whose mutations will be associated with albinism. In this review, we will describe the different types of albinism and comment on its prevalence in European countries. Some preclinical attempts for innovative therapeutic approaches of different types of albinism will be also discussed.
Albinism is a generic clinical term describing an heterogeneous group of several types of rare congenital diseases globally characterized by decreased pigmentation in skin, hair and/or eyes, and associated with retinal and, hence, visual alterations. Eye abnormalities, the most important and handicapping traits for persons with albinism (besides the obvious hypopigmentation), include fovea hypoplasia, reduced pigmentation of retinal pigment epithelium cells, photoreceptor rod cell deficit, misrouting of the optic nerves at the chiasm, reduced pigmentation in the iris, photophobia and nystagmus.1,2 Several studies suggest that all known forms of albinism affect 1:17 000 newborns in Western societies, mostly North America and Europe, although frequencies ranging from 1:10 000–20 000 have been also reported2,3 and other prevalences apply in Asia.4,5 In some countries in Africa, due to consanguinity issues, the prevalence of albinism can be much higher.6 The characteristic retinal alterations result in visual abnormalities commonly associated with persons with albinism, including reduced visual acuity, impaired stereoscopic vision, photophobia, iris transillumination and poor night vision. In addition, strabismus, refractive errors and alterations in color perception are also frequent among persons with albinism. Skin hypopigmentation must be protected from sun exposure and sunburns, hence, the adequate use of clothes, hats and efficient sunscreens is strongly recommended. The effects of iris transillumination and photophobia may be avoided with the use dark glasses. The poor visual acuity and refractive errors can be corrected with glasses or contact lenses. Nystagmus can be fixed with eye muscle surgery and strabismus can be also solved by patching one eye.3 Most of these retinal alterations have been well reproduced in animal models, primarily genetically modified rodents, transgenic mice, where the relationships between genetic modifications and phenotype alterations have been investigated and produced a substantial increase in our current understanding of the albinism genetic condition.7,8