Albinism Health Dictionary

Also called hypo-pigmentation, this congenital or acquired disorder is one in which the skin loses its pigmentation because of reduced MELANIN production. It can be classi?ed into three groups: VITILIGO, ALBINISM and post-in?ammatory hypopigmentation.... depigmentation

They may be local to the SKIN, or a manifestation of systemic disorders – inherited or acquired. Some major types are described below.

Others appear under their appropriate alphabetical headings: ACNE; ALBINISM; ALOPECIA; ALOPECIA AREATA; APHTHOUS ULCER; BASAL CELL CARCINOMA; BOILS (FURUNCULOSIS); BOWEN’S DISEASE; CALLOSITIES; CANDIDA; CHEILOSIS; CHEIRAPOMPHOLYX; DANDRUFF; DERMATOFIBROMA; DERMATOMYOSITIS; DERMATOPHYTES; DERMOGRAPHISM; ECTHYMA; ERYSIPELAS; ERYTHEMA; ERYTHRASMA; ERYTHRODERMA; ESCHAR; EXANTHEM; FUNGAL AND YEAST INFECTIONS; HAND, FOOT AND MOUTH DISEASE; HERPES GENITALIS; HERPES SIMPLEX; HERPES ZOSTER; IMPETIGO; INTERTRIGO; KELOID; KERATOSIS; LARVA MIGRANS; LICHEN; LUPUS; MADURA FOOT; MELANOMA; MILIARIA; MOLLUSCUM CONTAGIOSUM; MOLE; MYCOSIS FUNGOIDES; NAEVUS; ORF; PEDICULOSIS; PEMPHIGUS; PHOTOCHEMOTHERAPY; PHOTODERMATOSES; PITYRIASIS; PORPHYRIAS; PRURITUS; PSORIASIS; RINGWORM; ROSACEA; SARCOIDOSIS; SCABIES; SCLERODERMA; URTICARIA; VITILIGO; WARTS; XANTHOMATA.

Skin cancer Primary cancer is common and chronic exposure to ultraviolet light is the most important cause. BASAL CELL CARCINOMA is the most common form; squamous cell carcinoma is less common and presents as a growing, usually painless nodule which may ulcerate. Squamous cancer may spread to regional lymph glands and metastasise, unlike basal cell cancer. Occupational exposure to chemical carcinogens may cause squamous carcinoma – for example, cancer from pitch warts or the scrotal carcinoma of chimney sweeps exposed to coal dust in earlier centuries. Squamous carcinoma of the lip is associated with clay-pipe smoking.

Cancer may arise from the population of melanocytes of the skin (see MELANOCYTE; MELANOMA).

Apart from these three most frequent forms of skin cancer, various forms of cancer can arise from cells of the dermis, of which LYMPHOMA is the most important (see also MYCOSIS FUNGOIDES).

Lastly, secondary deposits from internal cancer, particularly from the breast, may metastasise to the skin.

Dermatitis and eczema These are broadly synonymous, and the terms are frequently interchangeable. Eczema is a pattern of in?ammation with many potential causes. Dermatitis is commonly used to suggest an eczema caused by external factors; it is a common pattern of in?ammation of the skin characterised by redness and swelling, vesiculation (see VESICLE), and scaling with intense itching and often exudation (weeping). Fissuring, thickening (licheni?cation – see LICHEN) and secondary bacterial infection may follow. Dermatitis can affect any part of the body. It may be genetically detemined or due to other ‘internal’ factors, such as venous HYPERTENSION in a leg, or stress. Often it is ‘external’ in origin – due to strong irritants or chemical allergens. (See also ALLERGY; ALLERGEN.) ATOPIC DERMATITIS is genetic in origin and usually begins in infancy. It may persist for years, and ASTHMA, allergic RHINITIS and conjunctivitis (see under EYE, DISORDERS OF) – ‘hay fever’ – may be associated. Atopic children tend to have multiple allergies, especially to inhaled allergens such as house-dust mite, cat and dog dander and pollens. Allergy to foods is less common but potentially more dangerous, especially if to nuts, when it can cause acute URTICARIA or even ANAPHYLAXIS. Atopic subjects are particularly prone to persistent and multiple verrucae (see WARTS) and mollusca (see MOLLUSCUM CONTAGIOSUM) and to severe HERPES SIMPLEX infections. (See also ATOPY.)

EXFOLIATE DERMATITIS (PITYRIASIS RUBRA)

Generalised exfoliation and scaling of the skin, commonly with ERYTHEMA. Drugs may cause it, or the disorder may be linked with other skin diseases such as benign dermatoses and lupus erythematosus (see under LUPUS). SUMMER POMPHOLYX is an acute vesicular eczema of the palms and soles recurring every summer. Inhaled allergens are a frequent cause. VENOUS (STASIS) DERMATITIS begins on a lower calf, often in association with PURPURA, swelling and sometimes ulceration. Chronic venous hypertension in the leg, consequent on valvular incompetence in the deep leg veins owing to previous deep vein thrombosis (see VEINS, DISEASES OF), is the usual cause. NEURODERMATITIS A pattern of well-de?ned plaques of licheni?ed eczema particularly seen on the neck, ulnar forearms or sides of the calves in subjects under emotional stress. IRRITANT CONTACT DERMATITIS Most often seen in an industrial setting (occupational dermatitis), it is due to damage by strong chemicals such as cutting oils, cement, detergents and solvents. In almost all cases the hands are most severely affected. ALLERGIC CONTACT DERMATITIS, in contrast, can affect any part of the body depending on the cause – for example, the face (cosmetics), hands (plants, occupational allergens) or soles (rubber boots). Particularly common allergens include metals (nickel and chromate), rubber addititives, and adhesives (epoxy resins).

Treatment Avoidance of irritants and contact allergens, liberal use of EMOLLIENTS, and topical application of corticosteroid creams and ointments (see CORTICOSTEROIDS) are central.... skin, diseases of

Abnormal paleness of the skin and mucous membranes, particularly noticeable in the face. Pallor is not always a symptom of disease. It may be due to a deficiency of the skin pigment melanin that may affect people who spend very little time in daylight. It is also a feature of albinism. In addition, pallor may be caused by constriction of small blood vessels in the skin, which may occur in response to shock, severe pain, injury, heavy blood loss, or fainting.Disorders that cause pallor include anaemia, pyelonephritis, kidney failure, and hypothyroidism. Lead poisoning is a rare cause.... pallor

n. an individual lacking the normal body pigment (melanin). See albinism.... albino

a rare fatal hereditary (autosomal *recessive) condition causing enlargement of the liver and spleen, albinism, and abnormalities of the eye. It is thought to be due to a disorder of glycolipid metabolism. [A. Chediak (20th century), Cuban physician; O. Higashi (20th century) Japanese paediatrician]... chediak–higashi syndrome

Abnormalities that are obvious at birth or detectable early in infancy. Also called congenital defects, they encompass both minor abnormalities, such as birthmarks, and serious disorders such as spina bifida.

Causes include chromosomal abnormalities, genetic defects, drugs taken during pregnancy, exposure to radiation, and infections. In some cases, the cause of a defect is unknown. Defects that are due to chromosomal abnormalities include Down’s syndrome. Some defects, such as achondroplasia and albinism, are usually inherited from 1 or both parents (see gene; genetic disorders). Certain drugs and chemicals (called teratogens) can damage the fetus if the mother takes or is exposed to them during early pregnancy. Teratogenic drugs include thalidomide (now rarely prescribed) and isotretinoin, which is used in the treatment of severe acne. Alcohol can affect the development of the brain and face (see fetal alcohol syndrome).

Irradiation of the embryo in early pregnancy can cause abnormalities. Very small doses of radiation increase the child’s risk of developing leukaemia later in life (see radiation hazards).

Certain illnesses, such as rubella (German measles) and toxoplasmosis, can cause birth defects if they are contracted during pregnancy.

Brain and spinal cord abnormalities, such as spina bifida and hydrocephalus, and congenital heart disorders (see heart disease, congenital) result from interference with the development of particular groups of cells. Other common defects include cleft lip and palate.

Ultrasound scanning and blood tests during pregnancy can identify women at high risk of having a baby with a birth defect. Further tests such as chorionic villus sampling, amniocentesis, or fetoscopy may then be carried out.... birth defects

Many eye disorders are minor, but some can cause loss of vision unless treated. (See also cornea, disorders of; retinal detachment.)

Squint is sometimes present at birth. Rarely, babies are born with microphthalmos. Other congenital disorders that affect the eye are nystagmus, albinism, and developmental abnormalities of the cornea and retina.

Conjunctivitis is the most common eye infection and rarely affects vision. Trachoma or severe bacterial conjunctivitis can impair vision. Corneal infections can lead to blurred vision or corneal perforation if not treated early. Endophthalmitis (infection within the eye) can occur as a result of eye injury or infection elsewhere in the body.

Narrowing, blockage or inflammation of the blood vessels of the retina may cause partial or total loss of vision.

Malignant melanoma of the choroid is the most common cancerous tumour of the eye. Retinoblastoma is a cancerous tumour of the retina that most commonly affects children.

Various vitamin deficiencies (particularly of vitamin A) can affect the eye. This may lead to xerophthalmia, night blindness, or, ultimately, keratomalacia.

Uveitis may be caused by infection or an autoimmune disorder such as ankylosing spondylitis and sarcoidosis.

Macular degeneration of the retina is common in the elderly, as is cataract.

Glaucoma, in which the pressure inside the eyeball becomes raised, can lead to permanent loss of vision. In retinal detachment, the retina lifts away from the underlying layer of the eye.Ametropia is a general term for any focusing error, such as astigmatism, myopia, or hypermetropia. Presbyopia is the progressive loss with age of the ability to focus at close range. Amblyopia is often due to squint.... eye, disorders of

A condition in which there is involuntary movement of the eyes.

In the most common type, jerky nystagmus, the eyes repeatedly move slowly in one direction and then rapidly in the other. Less commonly, nystagmus is “pendular”, with the eyes moving evenly from side to side.

Nystagmus may be congenital, in which case the cause is unknown. It also occurs in albinism and as a result of any very severe defect of vision present at birth, such as congenital cataract.

Persistent nystagmus appearing later in life usually indicates a nervous system disorder (such as multiple sclerosis, a brain tumour, or an alcohol-related disorder), or a disorder of the balancing mechanism in the inner ear. Adultonset nystagmus is occasionally seen as an occupational disorder in people who work in poor light.

Electronystagmography, a method of recording eye movements, may be used to identify the type of nystagmus.... nystagmus

Coloration of the skin, hair, and iris of the eyes by melanin. The more melanin present, the darker the coloration. Blood pigments can also colour skin (such as in a bruise).

There are many abnormalities of pigmentation.

Patches of pale skin occur in psoriasis, pityriasis alba, pityriasis versicolor, and vitiligo.

Albinism is caused by generalized melanin deficiency.

Phenylketonuria results in a reduced melanin level, making sufferers pale-skinned and fair-haired.

Areas of dark skin may be caused by disorders such as eczema or psoriasis, pityriasis versicolor, chloasma, or by some perfumes and cosmetics containing chemicals that cause photosensitivity.

Permanent areas of deep pigmentation, such as freckles and moles (see naevus), are usually due to an abnormality of melanocytes.

Acanthosis nigricans is characterized by dark patches of velvet-like, thickened skin.

Blood pigments may lead to abnormal colouring.

Excess of the bile pigment bilirubin in jaundice turns the skin yellow, and haemochromatosis turns the skin bronze.... pigmentation