Acanthosis nigricans is associated with numerous conditions, including obesity, type 2 diabetes, polycystic ovary syndrome and insulinoma. It is a hyperpigmented velvety overgrowth of the epidermis, which usually occurs in the flexural areas of the axilla, groin and neck (Figure 24.9). Increased circulating insulin levels act via insulin-like growth factor-1 (IGF-1) receptors in the skin to stimulate growth.
Various other skin problems are associated with longstanding diabetes, but are not specific to diabetes. These include bacterial infections (e.g. boils and sepsis caused by Staphylococcus aureus), Candida albicans infections (e.g. vulvovaginitis, balanitis, intertrigo and chronic paronychia) and tinea (dermatophyte fungal infections) (Figure 24.10). Note also the occurrence of neuropathic and ischaemic foot ulcers in diabetes (see Chapter 21), and the dry skin caused by decreased sweating with autonomic neuropathy.
Chronic paronychia presents with swelling and erythema around the nailfolds, with a discharge (Figure 24.11). Severe involvement may produce onycholysis. Treatment is by keeping the fingers dry and the use of antifungal drugs; systemic drugs such as terbinafine, as well as topical medications, may be necessary.
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Rudy Bilous MD, FRCP, Professor of Clinical Medicine, Newcastle University, Honorary Consultant Endocrinologist, South Tees Foundation Trust, Middlesbrough, UK Richard Donnelly MD, PHD, FRCP, FRACP, Head, School of Graduate Entry Medicine and Health, University of Nottingham, Honorary Consultant Physician, Derby Hospitals NHS Foundation Trust, Derby, UK
A John Wiley & Sons, Ltd., Publication This edition first published 2010, © 2010 by Rudy Bilous and Richard Donnelly. Previous editions: 1992, 1999, 2004
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