Even if you've had diabetes for a long time, chances are you've never heard of Necrobiosis Lipoidica Diabeticorum (NLD). In fact, the condition is so unusual that it's not even listed in the Merck Manual Home Health Handbook, which lists just about every imaginable malady you can possibly think of.

The good news is that it's relatively rare. "It's a rather uncommon skin lesion," says Michael Bergman, MD, clinical professor in the Department of Medicine at NYU Langone Medical Center. "Usually it appears on the lower extremities."

The skin disorder nearly always occurs in diabetics, and it's more likely to afflict women than men. Though it's not a life-threatening condition, it can be trying on those who have it, and unfortunately, it tends to stick around.

The rash typically presents on the legs, explains Paolo Romanelli, MD, of the Diabetes Research Institute in Hollywood, Florida. It usually occurs on both legs, not just one. It shows up as in several areas as raised, brownish-reddish patches. The centers, which tend to be yellow, may turn into open sores that don't heal easily. Though the rash is typically on the legs, it can also crop up in other areas like the forearms, on the torso, and even on a surgical scar.

Treatment of NLD

When the doctor's unsure of whether or not it is in fact NLD, a biopsy will be performed to get a definitive diagnosis. To treat it, doctors typically prescribe a topical cortisone cream. Sometimes ultraviolet light treatments may bring relief, as well.

"Treatment is very difficult," Bergman says. "People have tried injections of steroids and they've tried using aspirin. Nothing seems to really work."

Fortunately, NLD seems to wax and wane. It may be dormant for awhile and then flare up, which can be frustrating to the patient. "While it may not go away entirely, it can fade," Bergman says. "It's really a cosmetic thing. People have gone to plastic surgeons to have it treated, but it can recur and there can be scarring from a procedure."

If you're not diabetic and you develop the symptoms of NLD, see a dermatologist, advises Romanelli. Since the condition tends to primarily affect diabetics, doctors who diagnose NLD in a patient will often suspect diabetes, too. 

About 5 percent of people with type 1 diabetes have NLD, estimates Bergman, adding that it does not appear to be related to the length of time you've had diabetes. Nor does NLD appear to be linked to how well your diabetes is controlled. Bergman's advice? Seek treatment if you suspect that you may have NLD, and try various treatments to see what works for you.