Oculocutaneous Albinism - Literature review Example

?Oculocutaneous Albinism Introduction Any health illness that is caused due to abnormalities in genes or chromosomes is known as genetic disorder. Genetic disorder may be heritable or non-heritable. Genetic disorders can affect any system of the body including skin. Some of the skin genetic disorders are albinism and psoriasis. Albinism is a typical hereditary skin disease with varied clinical presentation and inheritance. It is mostly present from birth and increases the risk of cancer. It is not curable and there is no specific treatment. It can be a part of syndromes which cause bleeding diathesis and recurrent infections (Okulicz, 2002). In this article, a specific type of albinism, the oculocutaneous type will be discussed. Albinism Albinism is a group of disorders that are hereditary in nature and are related to abnormality in the synthesis or distribution of melanin (Okulicz, 2002). The abnormality of pigmentation manifests in eyes with or without involvement of skin and hair (Park et al, 2012). Thus, clinically, there are 2 categories of albinism. They are ocular albinism where in eyes are involved and skin involvement is either absent or minimal, and oculocutaneous albinism in which skin and eyes are involved. Oculocutaneous albinism may be defined as "a group of congenital heterogeneous disorders in which there is either complete or partial absence of pigment in the skin, hair and eyes because of the absence of or a defect in an enzyme involved in the production of melanin" (Park et al, 2011). In both the conditions, the primary morbidity is related to the eye. The pattern of inheritance in albinism is variable. While the ocular albinism is through autosomal recessive or sex-linked inheritance, oculo-cutaneous albinism is autosomal recessive (Park et al, 2012). Majority of the patients present in the infancy period. They present with discoloration of the eyes, skin and hair. In ocular albinism patients, the abnormalities related discoloration may not be obvious. Other clinical features include photophobia, high refractive errors, nystagmus, decreased vision and strabismus. Nystagmus and decreased vision occur due to foveal hypoplasia and strabismus occurs due to erratic decussation of fibers of optic nerve. Due to abnormalities in the optic pathway, poor stereopsis and monocular vision can occur (Park et al, 2012). In patients with Hermansky-Pudlak syndrome, easy bruising is seen and in those with Chediak-Higashi syndrome, recurrent infections are noted. In X-linked ocular albinism, decreased hearing is seen (Okulicz, 2002). As far as discoloration of eyes, skin and hair is concerned, the range of depigmentation is variable and depends on the type of albinism. The color of the iris is usually blue and can even be brown. The iris will have transillumination defects. The fundus also, in general, is hypopigmented. To broadly classify, there are 2 forms of albinism. The classification is based on the tyrosinase hair bulb incubation test which differentiates between the tyrosinase-positive and tyrosinase-negative forms. In those who are tyrosinase-positive, some degree of production of pigments occurs. In those who are tyrosinase-negative, there is absolutely no pigment production (Okulicz, 2002). Oculocutaneous albinism There are four types of oculocutaneous albinism or OCA (Okulicz, 2002). OCA type 1A is the classic tyrosinase negative type of OCA. In this condition, the infant is born with blue-grey irides, pink colored skin, white hair and predominant red reflex (Wei et al, 2011). The individuals have manifestations of the defects of eye as discussed above. They never develop pigmented lesions like freckles, naevi or lentigines. Hair becomes yellow with age due to denaturation of the keratin following exposure to ultraviolet light. In type1B, the presentation features at birth are similar to those in type 1A. However, as the age advances, the hair color darkens to brown color. The skin can get tanned on exposure to sunlight and can even develop pigmented lesions like naevi and freckles. The changes in color is mainly related to production of dopaquinone is the early melanin pathway. Type1B is mainly seen is Arnish population (Okulicz, 2002). The second type of oculocutaneous albinism is type2. Individuals with this condition have pigmented hair, eyes and skin at birth, also of lighter color. Pigmented birthmarks may also be there. As age advances, the pigmentation may increase and albinism appears inapparent. This condition is predominantly seen in African-American and African individuals (Okulicz, 2002). As the pigmentation increases, the red reflex in the eyes can decrease. When compared to type-1 defects in the eye are less severe, although, visual acuity may be impaired. In type 3 OCA, the skin is brick-red in color, hair is ginger or reddish and eyes are brown or hazel colored. Disturbances related to vision are minimal. Pigmented lesions can be present. This condition is mainly attributed to tyrosinase-related protein defects. In Hermansky–Pudlak syndrome or HPS, ceroid-like pigment gets accumulated in the reticulo-endothelial system contributing to bleeding diathesis. The albinism is tyrosinase positive. It is usually found in those from Puerto-Rican descent. Skin color varies and pigmentation increases as age advances. Common bleeding manifestations include bleeding from nose and from gums. Deposition of ceroid can lead to granulomatous colitis and pulmonary fibrosis. Individuals with OCA are increased risk of development of skin cancer (Okulicz, 2002). Diagnosis and treatment The diagnosis is mainly on clinical examination. Tyrosinase hair bulb incubation test may be needed to differentiate between tyrosinase positive and tyrosinase negative cases. Blood clotting tests may be done is there is suspicion of Hermansky-Pudlak syndrome. Confirmation of diagnosis of albinism may be done by visual evoked potential. Due to misrouting at the optic pathway level, patients will demonstrate asymmetry of VEP between the eyes. As of now, there is no treatment for albinism. The main stay of management is to provide photoprotection to prevent cancers of the skin. Correction of refractive errors needs to be done (Okulicz, 2002). Conclusion Albinism is one of the rare genetic skin disorders that manifests in infancy or even at birth. The main clinical presentation is in eyes and presents with wide spectrum of disorders involving the eyes. Based on the type skin and hair can also get involved. Again, the mode of inheritance, depends on the type of disorder. There is no treatment for albinism. The main complication is skin cancer. Hence preventive measures against skin cancer must be undertaken. References Kagore, F., and Lund, P.M. (1995). Oculocutaneous albinism among school children in Harare, Zimbabwe. J Med Genet., 32, 859-861. Okulicz, J.F., Shah, R.S., Schwartz, R.A., and Jnniger, C.K. (2002). Oculocutaneous albinism. JEADV, 17, 251–256. Park, S.H., Chae, H., Kim, Y., and Kim, M. (2012). Molecular analysis of Korean patients with oculocutaneous albinism. Jpn J Ophthalmol, 56, 98–103. Wei, A., Yang, X., Lian, Li, W. (2011). Implementation of an optimized strategy for genetic testing of the Chinese patients with oculocutaneous albinism. Journal of Dermatological Science 62 (2011) 124–127. Read More