Necrobiosis lipoidica: symptoms, causes and treatment

Necrobiosis lipoidica (often shortened to NLD) is a skin condition in which patches of altered, thinned skin develop, most often on the front of the shins. BAD explains that it follows damage to the collagen fibres that give the skin its strength, and that some think this is due to changes in the small blood vessels of the skin.

DermNet, an international dermatology resource, describes it as a rare granulomatous skin disorder typically described on the shin of people with diabetes, and notes that its cause is unknown, with theories including blood vessel changes similar to those seen in diabetes.

It is a long-term skin problem rather than an infection or a cancer. BAD says it is not contagious or cancerous. Knowing this can be reassuring when the patches are visible and persistent.

BAD says patches usually start as one or more small, red, slightly raised patches on one or both shins. Much less often they appear on other parts of the legs, and even on the hands, arms, trunk or face. They grow slowly and may join up to form larger, flatter, irregular patches with a well-defined red border and a shiny, yellowish centre with visible blood vessels.

Usually there are no symptoms other than the appearance, although DermNet says patches may be tender and may show reduced sweating and sensation. Because the skin is thin and the patches are persistent, the skin can break down and form ulcers that may be sloughy and infected. DermNet says ulceration complicates about one in three cases, usually following minor injury.

• Shiny, reddish-brown or yellowish patches, usually on the shins.

• A well-defined red border and a shiny, thin, yellowish centre with visible blood vessels.

• Thin skin that breaks down easily after minor knocks.

• Painful ulcers that are slow to heal.

BAD says the cause is not fully understood. It affects all races and can occur at any age, and is three times more common in women than in men. It appears to be slightly more common in type 1 than type 2 diabetes, and BAD adds that its occurrence does not seem to be related to glucose control.

DermNet reports that 11 to 65 per cent of patients with necrobiosis lipoidica have diabetes or prediabetes, and lists other associations including obesity, high blood pressure, raised blood fats and thyroid disease. BAD says tests for diabetes may be suggested for people who have necrobiosis lipoidica but are not known to have diabetes.

BAD says the appearance is often enough for diagnosis. If there is any doubt, a small skin sample (biopsy) may be taken under local anaesthetic and examined under a microscope. DermNet adds that the biopsy shows a characteristic granulomatous inflammatory reaction around damaged collagen, and lists other conditions that can look similar, such as sarcoidosis and necrobiotic xanthogranuloma.

A GP may refer you to a dermatologist. If you do not already have diabetes, a blood test for diabetes is a reasonable part of the work-up.

BAD stresses that treatments work best in the early stages, before scarring has developed, but the results are unpredictable. It is reasonable not to treat if there are no symptoms or ulceration. Rarely, the condition may heal on its own, in up to 17 per cent of people according to BAD, though even then permanent colour changes and skin thinning are likely.

BAD advises protecting the patches from injury to reduce the risk of ulceration, for example with a padded dressing, elastic support stockings or shin guards. If the patches are distressing, cosmetic camouflage is an option and professional help is available to find the best colour match; BAD mentions the charity Changing Faces and the Skin Camouflage Network.

If you have diabetes, BAD says it is best to keep it under good control; there is little evidence that this helps the necrobiosis itself but it may limit the risk of infection if patches ulcerate. Stopping smoking is important to reduce the risk of ulceration and improve wound healing.

BAD also says that if a lump, persistent scab or ulcer develops in an area of necrobiosis lipoidica you should consult your doctor without delay, because an early skin cancer is very easily treated.

On the NHS, a GP can make or suspect the diagnosis, arrange diabetes checks and refer to a dermatologist for difficult or ulcerating disease. Ulcers need wound care, which a GP practice or community nursing team can arrange.

Private dermatology is an option for people who want to be seen sooner or want to discuss treatment such as light therapy. Because evidence for treatment is limited and results unpredictable, it is worth asking any practitioner what outcome is realistic and how long a treatment should be tried before reviewing it.