Chromosome breaks and sister chromatid exchanges in albinos in Nigeria

Oculocutaneous albinism in sub-Saharan Africa: adverse sun-associated health effects and photoprotection

Oculocutaneous albinism (OCA) is a genetically inherited autosomal recessive condition. Individuals with OCA lack melanin and therefore are susceptible to the harmful effects of solar ultraviolet radiation, including extreme sun sensitivity, photophobia and skin cancer. OCA is a grave public health issue in sub-Saharan Africa with a prevalence as high as 1 in 1000 in some tribes. This article considers the characteristics and prevalence of OCA in sub-Saharan African countries. Sun-induced adverse health effects in the skin and eyes of OCA individuals are reviewed. Sun exposure behavior and the use of photoprotection for the skin and eyes are discussed to highlight the major challenges experienced by these at-risk individuals and how these might be best resolved.

Was skin cancer a selective force for black pigmentation in early hominin evolution?

Melanin provides a crucial filter for solar UV radiation and its genetically determined variation influences both skin pigmentation and risk of cancer. Genetic evidence suggests that the acquisition of a highly stable melanocortin 1 receptor allele promoting black pigmentation arose around the time of savannah colonization by hominins at some 1-2 Ma. The adaptive significance of dark skin is generally believed to be protection from UV damage but the pathologies that might have had a deleterious impact on survival and/or reproductive fitness, though much debated, are uncertain. Here, I suggest that data on age-associated cancer incidence and lethality in albinos living at low latitudes in both Africa and Central America support the contention that skin cancer could have provided a potent selective force for the emergence of black skin in early hominins.

Sun exposure and non-melanocytic skin cancer

Non-melanocytic skin cancer has long been regarded as one of the harmful effects of solar ultraviolet (UV) radiation on human health. In this review, we examine epidemiologic evidence linking sun exposure and skin cancer coming from both descriptive studies in populations and analytical studies involving estimates of exposure in individuals. Particular attention is given to the quality of the published data. The epidemiologic evidence that sun exposure causes skin cancer is mainly indirect. Incidence or mortality is inversely related to latitude in populations of mainly European origin (e.g., the United States, Australia), and is higher in people born in Australia (high ambient solar radiation) than in migrants to Australia from the United Kingdom (lower ambient radiation). Skin cancer occurs mainly at sun-exposed body sites and in people who are sensitive to the sun; a reduced capacity to repair UV-induced DNA damage appears to increase the risk. The direct evidence linking sun exposure and skin cancer is weaker with few well-conducted studies of sun exposure in individuals. Mostly, studies of total sun exposure have not found statistically significant positive associations; those that did, had not adjusted for potential confounding by age and gender and thus their interpretation is limited. Studies of occupational sun exposure had relative risks not greater than 2.0; recreational exposure has been little studied. Other measurements, less direct but potentially less prone to measurement error, are sunburn (not evidently associated with skin cancer risk) and indicators of benign cutaneous sun-damage (strongly associated but lacking empirical evidence that sun exposure is their main cause). Many questions remain about the relationship between sun exposure and skin cancer.

Albinism and skin cancer in Southern Africa

The presence of skin cancer was investigated in 111 albinos belonging to the black (Negro) population of Johannesburg, South Africa. The overall rate was 23.4%, the risk increasing with age. Identifiable risk factors included: environmental exposure to ultraviolet radiation; inability to produce ephelides ('freckles'); and possibly ethnicity. The head was the site most commonly affected, and squamous was far more common than basal cell carcinoma. No melanomas were detected. Recommendations are made regarding prevention of skin cancer in the at-risk group.

Sister chromatid exchanges in lymphocytes of patients with oral carcinoma

Sister chromatid exchanges (SCEs) were studied in cultured peripheral lymphocytes of 22 untreated patients with squamous cell carcinoma of the oral cavity and 29 age- and sex-matched controls. The SCE rate in cancer patients was not significantly higher compared with that found in controls, but there was a significant correlation between the SCE rate in lymphocytes of the cancer patients and the size of the primary tumor.

Albinism

Albinism is the term applied to a heterogeneous group of genetically determined disorders characterized by hypopigmentation and affecting the eyes. After describing the clinical features of albinism in general, the authors discuss the various forms of oculocutaneous albinism, ocular albinism, and albinoidism that are of interest to the ophthalmologist. Emphasis is placed on the ocular features of each form. The visual pathway abnormalities and the clinical management of albinism are discussed.

Hermansky-Pudlak syndrome: a clinicopathologic study

The Hermansky-Pudlak syndrome is a rare disease characterized by multisystemic involvement. Seven families with the disorder were identified in the Puerto Rican population of one municipal hospital, suggesting that the incidence in the Puerto Rican community is sufficient to warrant both dissemination of information about the disease and further investigation. The present study was an attempt to achieve both of these goals.

Comparative studies on spontaneous and mitomycin-C-induced sister-chromatid exchanges in smokers and non-smokers

Both spontaneous and mitomycin-C-induced sister-chromatid exchanges were analyzed in 6 smokers and 6 non-smokers. The average number of spontaneous SCE in smokers' cells was 8.33 +/- 1.08. The frequency in the non-smoking controls was 4.41 +/- 0.72. This difference is highly significant (P less than 0.001). Smokers also had more SCE at all levels of mitomycin C testes. Analysis of variance showed these differences to be highly significant (P less than 0.001).

Albinism in Nigeria with delineation of new recessive oculocutaneous type

Seventy-nine Nigerian oculocutaneous albinos were investigated. Fifty-six had typical tyrosinase-positive albinism (TPA) and 23 had brown albinism (BA), a new oculocutaneous type. The TPA were characterized by localized but no generalized skin pigment, yellow hair, blue to brown irides, nystagmus, and reduced or absent retinal pigment. Localized skin pigment included freckles and lentigines. The iris and skin pigment were the result of the slow accumulation of pigment with age as both were found in older individuals. The most severe skin changes were premalignant keratoses and squamous cell carcinoma of the skin, and the skin malignancies were the major factor in limiting the lifespan for TPA. The BA were characterized by generalized light brown skin pigment, light brown hair, blue to brown irides, nystagmus, and reduced retinal pigment. There was little accumulation or change of pigment in the eyes or skin with age. The generalized light skin pigment was effective in reducing sensitivity to solar radiation and very few BA had premalignant keratoses. Pedigree analysis for BA suggested on autosomal recessive inheritance pattern.