25 year old diabetic woman has yellow/orange waxy patches on her shins.

What's Your Diagnosis?

Diagnosis:
NECROBIOSIS LIPOIDICA DIABETICORUM ("NLD")

Definition:
A granulomatous inflammatory process characterized clinically by patches that become yellowish plaques and that in time resolve with atrophy and telangiectases. The condition occurs almost exclusively in persons with diabetes.

Adjuctive Diagnostic Test
Examinations should be undertaken to detect diabetes mellitus if not previously diagnosed.

Course:
Necrobiosis lipooidica begins, like virtually all inflammatory diseases, as a macule that becomes either a patch or a papule and eventually a plaque. For years the plaques expand slowly centrifugally and, in time, assumes a yellowish cast. Ulceration may supervene. After many years, the plaque involutes as an atrophic patch that maintains its yellowish cast and is joined by innumerable telangiectases.

Integration: Unifying Conept
An evolving reddish macule/patch of necrobiosis lipoidica is characterized by a small-vessel vasculitis mediated by neutrophils. A mixed-cell infiltrate of neutrophils, lymphocytes, and plasma cells is present around blood vessels of the superficial and deep plexuses, as well as within the interstitium of the reticular dermis. As the lesion becomes a plaque, vasculitic changes no longer are apparent. In addition to perivascular and interstitial infiltrates of lymphocytes and plasma cells, there are zones in the reticular dermis of degeneration of collagen, which are surrounded by epithelioid histiocytes aligned in a palisade. In time, as a plaque continues to evolve, the zones of degenerated collagen are replaced by thick bundles of collagen that continue to be encircled by epithelioid histiocytes. Later still, the granulomatous infiltrate wanes, and by the time the lesion has become atrophic patch, all that remains are altered bundles of collagen in the reticular dermis, telangiectases in the upper part of the dermis, and deposits of lipid. The lipid deposits are not detectable in sections stained with hematoxylin and eosin, but only in fresh tissue strain by oil red O or Sudan black, where they can be observed just beneath the thinned epidermis.

Necrobiosis lipoidica is a distinctive pathologic process that often is a manifestation of the diabetic state. Many patients with necrobiosis lipoidica have overt diabetes, and many who do not have latent diabetes.

Therapy:
Intralesional injection of corticosteroids is effective for active lesions, that is, those evidenced by redness and elevation. That treatment prevents progression of the process and hastens regression of it. Corticosteroids should not be applied to, or injected into, atrophic patches because they only worsen atrophy.

Reference:
A CLINICAL ATLAS OF 101 COMMON SKIN DISEASES
With Histopathologic Correlation
A. BERNARD ACKERMAN, HELMET KERL, JORGE SANCHEZ, YING GUO, ANGELIKA HOFER, PAUL KELLY, TETSU KIMURA, GIOVANNI BORRONI,CHARLES CRUTCHFIELD, VOLKER STEINKRAUS, WOLFGANG WEYERS