Epidemiology of NLD
Necrobiosis lipoidica diabeticorum (NLD) is a rare granulomatous skin disorder that has a female predominance, with an approximate ratio of 3:1. It has been linked to diabetes mellitus; as up to 65% of NLD patients have diabetes or prediabetes; however, only 0.03% of patients with diabetes have NLD. The control of blood glucose levels usually does not have a significant effect on the course of NLD. In spite of that, diabetic patients with NLD do appear to have a higher rate of diabetes-related complications compared to diabetic patients without NLD.
Pathogenesis of NLD
The cause of NLD remains unknown. It is postulated that immunologically mediated vascular disease is the primary cause of the altered collagen seen in NLD. Other theories suggest that microangiopathic vessel changes seen in diabetic patients could contribute to the development of collagen degeneration and subsequent dermal inflammation.
Clinical features of NLD
NLD starts as red–brown papules that are typically multiple and symmetrical on both shins. Later, it progresses into yellow–brown, atrophic, telangiectatic plaques surrounded by raised, violaceous rims. Pretibial region is the typical anatomical site for NLD, and it is less commonly seen in other sites including upper extremities, face and scalp. NLD is typically asymptomatic; however, some patients report pruritus, dysesthesia or pain.
Diagnosis of NLD
NLD is diagnosed clinically when typical. A biopsy specimen from the palpable inflammatory borders is used to confirm the diagnosis. The histopathology is characteristic; it shows granulomatous epithelioid histiocytes arranged in a palisaded fashion around destroyed collagen (necrobiosis). The inflammation extends throughout the dermis and into subcutaneous fat septae.
Management of NLD
No treatment for NLD has proven to be effective. However, intralesional corticosteroids injected into the active borders of established lesions can be used as first-line treatment to halt disease progression and extension into the surrounding normal skin. In extensive ulcerations that are refractory to medical treatment, surgical management and skin grafting can be considered.
Complications of NLD
Ulceration is a common complication for NLD that is seen in 1/3 of the cases, usually preceded by a minor injury to an established patch. Secondary bacterial infection, delayed healing and squamous cell carcinoma have been reported to develop in ulcerated NLD.
Maee Barakeh, medical student
Bolognia textbook of dermatology