▶Represents epidermal proliferation process with minimal increase in melanin.
▶Believed to be due to insulin resistance and its effect on the skin.
▶May be seen in the following settings:
■Obesity
■Insulin resistance syndromes
■Endocrinologic disorders (eg, diabetes mellitus, Addison disease, Cushing disease, hypothyroidism, hyperand rogenism, hypogonadism, polycystic ovary syndrome)
■Medications (oral contraceptives, nicotinic acid)
▶Malignancy: In adults, sudden onset of acanthosis nigricans may herald a malignant tumor, but no such association recognized in childhood.
▶Velvety thickening of the skin creates a brown to gray-black color that may be mistaken by patients as dirt (Figure 67.1).
▶Most commonly observed on the nape or sides of the neck, axillae, and groin (crural creases); some patients may exhibit lesions over the knuckles (Figure 67.2) and around the mouth.
Look-alikes
Disorder | Differentiating Features |
•Lacks the velvety texture of acanthosis nigricans. | |
Lichenification (ie, thickening of the skin) associated with chronic atopic or contact dermatitis | •Lacks the velvety texture of acanthosis nigricans. •Other features of atopic dermatitis often present. •Pruritus common (acanthosis nigricans not pruritic). |
▶The diagnosis is made clinically based on the clinical appearance (ie, velvety thickening of skin) in typical locations.
▶Evaluate patient for underlying cause based on history and physical examination.
■Evaluate the patient for the possibility of diabetes mellitus type 2 and hyperlipidemia.
■Consider obtaining an insulin level or other endocrinologic testing if the patient does not have obesity.
▶Treatment of acanthosis nigricans is difficult and often unsatisfactory.
■Consider application of keratolytic preparation (ie, one containing lactic or salicylic acid) or a retinoid.
■Extensive acanthosis nigricans may benefit from carbon dioxide laser resurfacing.
■If otherwise indicated, metformin may improve acanthosis due to reduced insulin resistance.
■Changes often (but not always) improve with weight loss (and resultant improved insulin sensitivity).
Treating Associated Conditions
▶If an underlying disorder is identified in a patient who has acanthosis nigricans, it should be managed appropriately.
▶Acanthosis nigricans is an important marker for insulin resistance, hyperlipidemia, and metabolic syndrome.
▶Familial acanthosis nigricans has an excellent prognosis.
▶If associated with other disorders, the prognosis depends on the other conditions and is variable.
▶MedlinePlus: Information for patients and families (in English and Spanish) sponsored by the US National Library of Medicine and National Institutes of Health.
https://www.nlm.nih.gov/medlineplus/ency/article/000852.htm
▶WebMD: Information for families is contained in Skin Problems and Treatments.
www.webmd.com/skin-problems-and -treatments/acanthosis-nigricans-overview