There are granulomas in the dermis, forming a

The dermis and subcutis contains degenerated collagen.

Again, note the degenerated collagen. In contrast, rheumatoid nodules have degenerated fibrin.

A granulomatous response to degenerated collagen along with thickening of blood vessel walls (not shown here) characterize NDL.

Because they commonly occur in diabetic patient, necrobiosis lipodica is often called necrobiosis lipoidica diabeticorum (NLD).

Presents as red plaques which eventually become yellow-brown, most common on the shins (pretibial surfaces) of younger diabetics. The lesion can be telangietactic. Less than 1% of diabetes get these lesions. They are usually asymptomatic, but can occasionally be ulcerated, painful and pruritic.

Treatment may include dressings, topical and subcutaneous steroids, and acetylsalicylic acid and dipyridamole, or psoralen plus ultraviolet A photochemotherapy. New treatments also include cyclosporin A, infliximab or tacrolimus, used topically or systemically (Griffiths).

DLD is not necessarily correlated with glucose control and can be chronic. There are usually frequent flares, and no treatment is completely effective. Other patients may experience spontaneous remission. There have been rare reports of squamous cell carcinoma arising from these lesions (Barnes).