A dark brown to black, velvety or warty thickening appearing on the skin of the neck, underarms, groin, navel, and anogenital region. The changes are spaced evenly on both sides of the body and may involve more extensive areas, including the face, inner thigh, eyelids, and palms of the hands and soles of the feet. The velvety markings usually blend imperceptibly into the surrounding skin. Warty overgrowth generally is limited to mucous membranes—the mouth or anus—or to skin flexures at the groin and underarms.
There are four types of acanthosis nigrans:
In the adult, acanthosis nigrans is a “diagnostic marker’ it is a classic skin disease that heralds the pres- ence of an internal cancer, usually located within the abdomen. The skin condition clears when the tumor is removed and reappears if there is a recurrence.
In early infancy, the condition has no relation to any internal condition and is only of cosmetic importance.
In the adolescent, it is accompanied by changes in the endocrine system in one-third of the patients: diabetes, Addison’s disease, gigantism, acromegaly, or Stein-Leventhal syndrome.
At any age, in obese brunettes, it is less extensive than the cancer- indicating variety and it never appears on mucosal surfaces. Mild cases tend to disappear with weight reduction.