Acanthosis nigricans
Acanthosis nigricans is a brown to black, poorly defined, velvety hyperpigmentation of the skin. It is usually found in body folds, such as the posterior and lateral folds of the neck, the armpits, groin, navel, forehead, and other areas.
Classification
Acanthosis nigricans is conventionally divided into benign and malignant forms, although may be divided into syndromes according to cause:
Benign This may include obesity-related, hereditary, and endocrine forms of acanthosis nigricans.
Malignant. This may include forms that are associated with tumour products and insulin-like activity, or tumour necrosis factor.
An alternate classification system still used to describe acanthosis nigricans was proposed in 1994. It delineates acanthosis nigricans syndromes according to their associated syndromes, including benign and malignant forms, forms associated with obesity and drugs, acral acanthosis nigricans, unilateral acanthosis nigricans, and mixed and syndromic forms.
Signs and symptoms