An Unusual Clinico-Dermoscopic-Pathological Presentation of Necrobiosis Lipoidica in a Nondiabetic, Hypothyroid Woman.

Sir,

A 44-year-old housewife with skin phototype-IV presented with multiple asymptomatic hyperpigmented lesions on the bilateral legs and feet for the last 6 months, along with a nonhealing ulcer on the left leg for 2 months. There was no history of diabetes, hypertension, or systemic complaint. Cutaneous lesions were in the form of multiple reddish to reddish-brown papules and annular and targetoid indurated plaques. The targetoid plaques had a central normal-looking skin, middle brown-black pigmentation, and an outer reddish-brown indurated elevated border. The annular plaques showed a central brown-black pigmentation surrounded by a violaceous elevated border. The annular plaques showed multiple budding-like peripheral extensions that gave a “pilot's wheel” appearance [Figure 1a-c].

Figure 1

(a) Clinical picture of necrobiosis lipoidica dominated by pigmentary alteration. The arrow is pointing to the ulcer. (b) Targetoid plaque plaque with a central normal-looking skin, middle brown-black pigmentation, and outer active reddish-brown indurated border. (c) Pilot's wheel appearance with peripheral extension (arrow). (d) and (e) Erythematous papules gradually enlarging to form annular plaques with a central brown-black pigmentation during follow-up (arrows). (f) Healing of the ulcer following therapy (arrow).

During hospitalization, the erythematous papules gradually enlarged to form annular plaques with central brown-black pigmentation [Figure 1d and 1e]. In the middle third of both the legs, the lesions coalesced to form irregular reddish-brown to brown-black indurated plaques. Differential diagnoses of venous insufficiency, necrobiosis lipoidica (NL), pigmented purpuric dermatosis, and morphea were considered. Dermoscopy (Dermlite, DL4, ×10) under polarized mode demonstrated two patterns: early papules/plaques and the active border showed a yellow-orange homogenous area with or without shiny white structures, while the trailing healed area showed white homogenous area, light to dark brown blotch, pigment network, and dots, and occasional pink clods [Figure 2]. Laboratory investigations revealed iron deficiency anemia (Hb: 10.4 gm%) and hypothyroidism (TSH: 15.062 micro IU/L). Other investigations, including arterial and venous color Doppler study of bilateral lower limbs, were within normal limits.

Figure 2

Dermoscopic examination (Dermlite, DL4) under polarized mode of the early papule (a) and plaque (b) show yellow-orange homogenous area, shiny white structures (blue arrow), and pigment network (red arrow). (c) and (d) Targetoid plaque shows central pigment network (red arrow) and peripheral yellow-orange homogenous area, pink clods, shiny white structures (blue arrow), and peripheral white homogenous area (arrow). (e) Active border shows a yellow-orange homogenous area. (f) The inner zone shows a pigment network and brown to black blotch (arrow).

Histopathology from the active border showed mild acanthotic and hyperpigmented epidermis. The entire dermis and the upper subcutis displayed the presence of necrobiotic granulomas and fibrosis in a “cake layering pattern.” The areas of necrobiosis were surrounded by an ill-defined palisade of histiocytes and Langhans and foreign-body type of multinucleate giant cells [Figure 3]. Features of vasculitis and/or vasculopathy were evident in the small caliber vessels of dermis and upper subcutis in the form of endothelial swelling, endothelial proliferation, focal leukocytoclasia, RBC extravasation, perivascular lymphoplasmacytic infiltration, and intimomedial hypertrophy causing narrowing, and at places complete obliteration of the vascular lumen. Perls’ Prussian blue (PPB) stain highlighted a prominent perivascular and interstitial deposition of hemosiderin. Alcian blue stain did not reveal mucin deposition, and Verhoeff–Van Gieson stain (VVG) stain showed the absence of elastin in the fibrotic area [Figure 4].

Figure 3

Biopsy from the outer (a) and inner (b) border of the annular plaque show the presence of necrobiotic granuloma and fibrosis in a “cake layering pattern” in the dermis and upper subcutis (H & E, ×20, ×50). (c) Areas of necrobiosis (arrow) surrounded by palisading granuloma (H & E, ×100). (d) Granulomata shows Langhans giant cells (H & E, ×400). (e) Areas of fibrosis (H & E, ×100). (f) Perivascular plasma cells (arrow) in the subcutis (H & E, ×400).

Figure 4

(a) RBC extravasation (H & E, ×400). (b) Leukocytoclasis (arrow, H & E, ×400). (c) Endothelial proliferation and occlusion of the lumen (arrow, H & E, ×400). (d) Perivascular and interstitial deposition of hemosiderin (arrow, H & E, ×400). (e) Hemosiderin is highlighted by Perls’ Prussian blue stain (PPB stain, ×50). (f) Loss of elastic fiber highlighted by VVG stain (VVG stain, ×50).

The diagnosis of NL was established. Treatment with oral prednisolone (40 mg/day) was started and gradually tapered by 10 mg every 2 weeks, which led to the healing of the ulcers in 1 month [Figure 1f].

Well-defined reddish-yellow to yellow-brown annular plaque with erythematous border and shiny atrophic telangiectatic center is the hallmark morphology of NL.[1] In the present case, the clinical picture was dominated by pigmentary alteration, which was due to the extensive deposition of hemosiderin due to chronic vascular insult. The described clinical feature may divulge the clinical diagnosis from NL to more common pigmentary disorders such as venous insufficiency, pigmented purpuric dermatosis, and morphea, especially in skin of color.

The dominant dermoscopic features of NL are well-focused vessels of variable morphology over a diffuse or localized, yellowish-orange to white structureless area. The morphology of the vessels varies according to the evolution of the lesion and includes dotted, globular, comma (incipient lesions), network-shaped or hairpin-like (more developed lesions), or branching or serpentine (advanced lesions).[23] In this case, except for a few isolated pink clods, there was no vascular structure, which is atypical for NL.

The histomorphological features of NL are due to collagen degeneration, granulomatous inflammation, fibrosis, and destruction of adnexal structures. The lack of deposition of lipid and dilated vessels in our case explains the absence of dominant yellow color and telangiectasia clinically.

Magro et al.[4] demonstrated vasculitis or thrombogenic vasculopathy and extravascular neutrophilia in NL lesions. It was associated with underlying systemic disease and had an atypical clinical presentation. They postulated that the degeneration of collagen is due to tissue ischemia as a result of active vasculopathy. The role of vasculitis in the pathologic process of NL is further supported by the deposition of immunoreactive IgM and complement in the vessel wall, and at times along the dermo–epidermal junction.[5]

We report an unusual case of NL with atypical annular and pigmented targetoid morphology that resulted from chronic vasculopathy and associated hemosiderin deposition. In addition, telangiectatic vessels were absent, both clinically and dermoscopically.

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Conflicts of interest

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