Diagnosis is confirmed through a skin biopsy showing inflammatory cell infiltrate and necrotising vasculitis.

[citation needed] NL/NLD most frequently appears on the patient's shins, often on both legs,[1] although it may also occur on forearms, hands, trunk, and, rarely, nipple, penis, and surgical sites.

If an injury to the skin occurs on the affected area, it may not heal properly or it will leave a dark scar.

[citation needed] Although the exact cause of this condition is not known, it is an inflammatory disorder characterised by collagen degeneration, combined with a granulomatous response.

[4] NL is diagnosed by a skin biopsy, demonstrating superficial and deep perivascular and interstitial mixed inflammatory cell infiltrate (including lymphocytes, plasma cells, mononucleated and multinucleated histiocytes, and eosinophils) in the dermis and subcutis, as well as necrotising vasculitis with adjacent necrobiosis and necrosis of adnexal structures.

[medical citation needed] Although there are some techniques that can be used to diminish the signs of necrobiosis such as low dose aspirin orally, a steroid cream or injection into the affected area, this process may be effective for only a small percentage of those treated.