Acanthosis nigricans is a skin condition characterized by dark, thick, velvety skin in body folds and creases. Most often, acanthosis nigricans affects your armpits, groin and neck. There's no specific treatment for acanthosis nigricans. But treating any underlying conditions, such as diabetes and obesity, may cause skin changes to fade.

Symptoms 

• Skin changes are the only signs of acanthosis nigricans
• Skin is dark, thick, and velvety in body folds and creases typically in armpits, groin and neck
• Acrochordons (skin tags) are often found in and around the affected areas
• Sometimes the lips, palms or soles of the feet are affected as well
• Nail changes, such as leukonychia and hyperkeratosis, have been reported
• Rarely, the affected areas may itch
• Acanthosis nigricans of the oral mucosa or tongue is highly suggestive of a neoplasm, especially of the GI tract

Causes

• Insulin resistance- type II diabetes mellitus
• Obesity
• PCOS
• Endocrinopathies- hypothyroidism or hyperthyroidism, Cushing’s disease, acromegaly
• Familial
• Drug induced- human growth hormone, OCP, high dose niacin
• Idiopathic
• Malignant- gastric cancer, adeno carcinoma of uterus

 

Acanthosis is has been associated with numerous syndromes, particularly type A and type B syndrome

Type A syndrome

• The type A syndrome also is termed the hyperandrogenemia, insulin resistance, and acanthosis nigricans HAIR-AN syndrome).
• This syndrome is often familial, affecting primarily young women (especially black women).
• It is associated with polycystic ovaries or signs of virilisation (eg, hirsutism, clitoral hypertrophy).
• High plasma testosterone levels are common.

Type B syndrome

The type B syndrome generally occurs in women who have

• Uncontrolled diabetes mellitus
• Ovarian hyperandrogenism
• Systemic lupus erythematosus
• Scleroderma
• Sjögren syndrome
• Hashimotos thyroiditis

Tests and diagnosis

Screen for diabetes with a glycosylated hemoglobin level or glucose tolerance test.

A good screening test for insulin resistance is a plasma insulin level, which will be high in those with insulin resistance.

A skin biopsy may be needed in unusual cases.

Treatment

The goal of therapy is to correct the underlying disease process.

• Correction of hyperinsulinemia often reduces the burden of hyperkeratosis lesions.
• Weight reduction in obesity
• Topical medications that have been effective in some cases include keratolytics (eg, topical tretinoin).
• Oral agents that have shown some benefit include etretinate, isotretinoin, metformin, and dietary fish oils.
• Cyproheptadine has been used in cases of malignant acanthosis nigricans
• Dermabrasion and long-pulsed alexandrite laser therapy may also be used to reduce the bulk of the lesion.