1. Acanthosis nigricans
Acanthosis nigricans is a rash of velvety hyperpigmentation seen most commonly in the axillae. It is often associated with skin tags & may occur in other sites such as neck, groin , mouth, hands & perianal region. Histologically, it shows hyperkereatosis, acanthosis & papillomatosis.
1, Pseudo- acanthosis nigricans is most commonly seen in association with obesity & endocrine disorders such as diabetes & Cushing’s disease. It is thought that friction & maceration of the flexures plays a role in the disorder’s etiology.
2. Congenital acanthosis nigricans is inherited in an autosomal dominant manner. The rash often appears before puberty & may be associated with mental retardation & neurofibromatosis.
3. True acanthosis nigricans :is rare, it presents in non-obese adults & is always associated with cancer It is a poor prognostic sign usually associated with disseminated disease. Mouth & hand (Triple palm ) lesions are characteristic.

2. Acanthosis nigricans

3. Acanthosis nigricans
Oral acanthosis nigricans
N.Eng. J. Med. 2OO7:357

4. Acanthosis nigricans Classification
A. Schwartz classification:
Schwartz,R.A. :J. Am. Academy of Dermat. 31: 1, 1994
@ Benign acanthosis nigricans
@ Acanthosis nigricans associated with obesity
@ syndromic acanthosis nigricans @ Malignant acanthosis nigricans
@ Acral acanthosis nigricans. @ Unilateral acanthosis nigricans
@ Drug induced acanthosis nigricans @ Mixed acanthosis nigricand
B. James et al. Andrews “Diseases of the skin” Clinical dermatology Saunders 2OO5 1Oth edition
@ Acral acanthotic anomaly
@ Acanthosis nigricans type I ( in association with malignancy)
@ Acanthosis nigricans type II ( Familial acanthosis nigricans)
@ Acanthosis nigricans type III ( Acanthosis nigricans associated with obesity, insulin resistant states & endocrinopathy.

5. Acanthosis nigricans Classification
C. Judge et al. Rook’s textbook of dermatology Blackwell seventh edition 2OO4:
@ Inherited forms of acanthosis nigricans
@ Benign acquired acanthosis nigricans
@ HAIR -AN syndrome: The triad of hyperandroginism, insulin resistance & acanthosis nigricans in women is known as HAIR-AN syndrome
@ Autoimmune acanthosis nigrican
@ Drug – induced acanthosis nigricans
@ Malignancy associated acanthosis nigrican
@ Tripe palm: velvety rugose thickening of the palm is almost always associated with internal malignancy. By contrast, familial keratoderma associated with malignancy is compact & non- rugose.
@ Nevoid acanthosis nigricans