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Acanthosis nigricans_0912 Derm Dx
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A 39-year-old Hispanic woman complains of discolored skin around her mouth and nose. She is unsure how long it has been present.
The patient reports that she tried using a “bleaching cream” without improvement. Her past-medical history is significant for acne for which she previously took minocycline. She denies prescription medications but is currently drinking a daily homeopathic “weight-loss” tea.
On physical exam you note that the patient is overweight. A full body skin exam is performed and is significant for grey-brown patches on her nasal creases and oral commisures, between her breasts and on her neck. Laboratory evaluation including fasting blood glucose and HbA1C are normal. What’s your diagnosis?
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Acanthosis nigricans clinically appears as hyperpigmented plaques with a characteristic “velvety” texture. The lesions are distributed symmetrically and may involve multiple regions including the neck, face, groin, elbows, knees, extensor aspect of the finger joints, areolae and umbilicus. There may be oral mucosal involvement.
Blacks, Hispanics and Native Americans have a genetic predisposition to developing acanthosis nigricans. This risk is independent of obesity.
The most common type of acanthosis nigricans is associated with insulin-resistant states and obesity. Obesity, even in the absence of a detectable endocrinologic abnormality, is the single most common factor associated with acanthosis nigricans.
Other associations include diabetes, acromegaly, gigantism, polycystic ovarian syndrome and Cushing syndrome. HAIR-AN syndrome describes the association of acanthosis nigricans (AN) with hyperandrogenism (HA) and insulin resistance (IR).
Acanthosis nigricans is rarely associated with malignancy, but when it is the most common association is with stomach adenocarcinoma. In malignancy-associated acanthosis nigricans, the presentation is frequently extensive and pronounced. Malignancy should be suspected if widespread acanthosis nigricans develops in nonobese males aged older than 40 years.
Tripe palms — the velvety thickening of the palms — is frequently associated with acanthosis nigricans and is almost always associated with cancer. When tripe palms present in association with acanthosis nigricans, the most common malignancy is gastric cancer. When tripe palms present alone, the most common malignancy is lung cancer.
Another rare presentation of acanthosis nigricans is the hereditary variant, which presents at birth or develops during childhood. There is no association with cancer.
Diagnosis
Acanthosis nigricans can usually be diagnosed clinically by the presence of velvety hyperpigmented plaques in the typical distribution previously described. When the diagnosis is in doubt, a punch biopsy may be performed. The histopathology will show papillomatosis and hyperkeratosis. Ironically, acanthosis is not present on histology!
Treatment
Obesity-associated acanthosis may improve with weight loss. If associated with malignancy or endocrine abnormalities, treatment involves identifying and treating the underlying causes.
Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.
- Bolognia J, Jorizzo JL, Rapini RP. “Chapter 52: Dermatologic Manifestations in Patients with Systemic Disease.” Dermatology. St. Louis, Mo.: Mosby/Elsevier, 2008.
- James WD, Berger TG, Elston DM et al. ” Chapter 24: Endocrine Diseases.” Andrews’ Diseases of the Skin: Clinical Dermatology. Philadelphia: Saunders Elsevier, 2006.
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