Necrobiosis lipoidica diabeticorum (NLD) is a skin disease characterized by the destruction of connective and elastic tissue and the development of discolored areas that can cause scarring. The complex name alludes to the various aspects of the condition. Necrobiosis refers to degeneration of collagen, the fibrous protein that provides strength and structure to the skin. Lipoidica refers to lipids (fats) that form in the center of the lesion and give lesions a yellowish color. Diabeticorum refers to the association of NLD with diabetes.

NLD is estimated to affect less than 1 percent of patients with diabetes. It can occur before other signs of the onset of diabetes, such as in the early stages or after years of living with the disease. It also occurs, although less frequently, in people who do not have diabetes or a family history of the disease. When NLD is suspected, patients are advised to undergo screening such as glucose tests to determine whether the lesions are an early indicator of diabetes.

The disease is rare but can occur in nearly anyone. It is found in all races and ethnicities and in both sexes, though women are more likely to develop NLD than men. Lesions tend to start in patients in their 30s, but occurrence of lesions has been recorded at nearly any age.

The disease is difficult to treat and generally chronic. Patients may experience unpredictable periods of inactivity and flare-ups. In some cases, the lesions may heal without any treatment. When the skin lesions do not heal they may lead to complications that could become severe, such as ulcers and infection. The site of lesions should be protected to prevent scratches or other trauma to allow the ulcers to heal.

NLD is sometimes confused with other dermatological disorders. These include:

• Diabetic dermopathy. Scaly brown patches, usually occurring on the shins, due to changes in the small blood vessels caused by diabetes. These harmless patches do not hurt, itch or erupt and do not need treatment.
  
  
• Granuloma annulare. A ring- or arc-shaped rash, usually red or reddish-brown, that can be itchy. It can appear anywhere on the body but usually on areas far from the trunk, such as the hands or ears. The cause is unknown, but people with diabetes are prone to the condition. Treatments include corticosteroid medications and controlled exposure to ultraviolet light.
  
  
• Rheumatoid arthritis nodules. Small lumps that can appear near the joints of the upper and lower limbs of people who have rheumatoid arthritis. Rheumatoid arthritis is a painful, inflammatory autoimmune disease that causes damage to the joints.
  
  
• Eruptive xanthomatosis. Yellow pea-like bumps, each surrounded by a red ring, that appear on the skin in cases of uncontrolled diabetes. Eruptive xanthomatosis can itch and usually occurs on the backs of hands, feet, arms, legs and buttocks. It most frequently occurs in young men with type 1 diabetes who have hyperlipidemia (high levels of fat in the blood).