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Acanthosis Nigricans

Title               

Ñ    Acanthosis Nigricans

Definition

Types of Acanthosis Nigricans

Ñ    Obesity-associated acanthosis nigricans:

Weight dependent, insulin resistance

Ñ    Syndromic acanthosis nigricans (associated with syndrome):

·          Type A syndrome:

Hyperandrogenemia, insulin resistance, AN syndrome (HAIRAN syndrome)

·          Type B syndrome:

Diabetes mellitus, acromegaly, hypothyroidism, hyperthyroidism, polycystic ovaries, systemic lupus erythematosus, scleroderma, Sjögren’s syndrome, Hashimoto’s thyroiditis

Ñ    Acral:

Lesions most prominent over dorsal aspects of the hands and feet

Ñ    Unilateral

Ñ    Familial

Ñ    Drug-induced:

Nicotinic acid, insulin, pituitary extract, systemic corticosteroids, diethylstilboestrol, triazinate, oral contraceptives, fusidic acid, methyltestosterone

Ñ    Malignant:

Adenocarcinoma

Gastrointestinal origin

Usually gastric adenocarcinoma

Ñ    Mixed-type:

One type develops new lesions of a different type

Pathogenesis

Ñ    Increase in factors that stimulate growth of epidermal cells and dermal fibroblasts:

Insulin or insulin like growth factor in the benign types

Substance produced by tumour cells in the malignant type

Clinical Features

History

Race

Ñ    More common in races with darker skin

Age

Ñ    Any age

Sex

Ñ    Males = Females

IS

Ñ    Area of thickening and darkening of the skin

Ñ    Pruritus occasionally

Past Illnesses

Ñ    Relevant associated illness

Drug History

Ñ    Relevant associated drug

Examination

IS

Ñ    Pigmented, velvety thickening of the skin with skin tags:

Flexures, mainly

Investigations

Tissue Diagnosis

Skin Biopsy

Ñ    Hyperkeratosis, papillomatosis, irregular acanthosis

Ñ    Dermal papillae project upward as fingerlike projections, occasional thinning of the adjacent epidermis

Ñ    Pseudohorn cysts may be present

Management

Control

Drugs

Ñ    Topical or oral retinoids may help

Lifestyle Adjustments

Ñ    Diet, exercise to achieve weight loss

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