Dermoscopic evaluation of acroangiodermatitis (Pseudo-Kaposi sarcoma): A rare vascular phenomenon

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Pseudo-Kaposi sarcoma (PKS), or acroangiodermatitis (AAD), can be either congenital or acquired and usually involves the lower limbs. The characteristic feature is reactive vascular hyperplasia, brought on by chronic venous valve insufficiency and aberrant alterations in the microcirculation. This condition is sometimes mistaken for Kaposi sarcoma (KS).^[1]

Here, we are reporting two very rare and similar interesting cases. One patient in his early thirties reported swelling in his lower limbs that extended to the middle of the leg, as well as periodic pain in his lower limbs over the previous 2 years. This was linked to the recurring emergence of numerous swellings, which would ulcerate and leave bare regions. No family member had a comparable complaint. The patient had antiphospholipid syndrome but had recovered and was no longer taking any drugs. On examination, patients had lower limb pitting edema that extended to the proximal part of the lower limbs, primarily on the right side, and erythematous to violaceous plaques and papules of variable size and shape, as well as hyperpigmentation of the surrounding skin, which was slightly tender to the touch. There were also many scars and discoloration on the legs, indicating previously healed lesions [Figure 1a].

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Figure 1

(a): Multiple violaceous plaques (ill to well-defined borders) and papules over the right lower leg with diffuse edema extending proximally. Variable in size and shape, the largest measuring 4 cm × 4 cm, to the smallest measuring 1 cm × 1 cm. Hyperpigmentation (post-inflammatory) is present in the surrounding skin and areas of previously healed atrophic areas; (b): Multiple erythematous to violaceous plaques (well-defined borders) and papules over the right lower leg with diffuse edema extending proximally. Variable in size and shape, the largest measuring 2 cm × 2 cm, to the smallest measuring 0.5 cm × 0.5 cm, with superficial ulceration in some and erythema. Hyperpigmentation (post-inflammatory) is present in the surrounding skin and areas of previously healed atrophic areas.

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Another in his mid-twenties presented with swelling of lower limbs extending to the middle of the leg with occasional pain in his lower limbs for the past year. This was associated with the recurrent appearance of multiple swellings that used to ulcerate and leave behind raw areas. No family member had a similar complaint. The patient had a history of deep vein thrombosis. On examination, patients had lower limb pitting edema that extended to the proximal part of the lower limbs, more pronounced on the right side, and erythematous to violaceous papules and plaques of variable size and shape. Some had superficial ulceration and crusting, with regular margins and sloping edges. The floor of the ulcer was covered with slough, accompanied by erythema and hyperpigmentation of the surrounding skin, and was slightly tender on touch. There were also multiple scars and hyperpigmentation over the legs, suggestive of previously healed lesions [Figure 1b].

There was no clinical sign of palpable thrill or bruit, varicose veins, or lymphadenopathy. Peripheral pulses were felt, and the rest of the systemic examination was normal. Our close clinical differentials were lichen planus, chromoblastomycosis, and KS.

The dermoscopic pattern observed included brownish crusts, peripheral coppery dots, red globules, shiny white structureless areas, red lacunae, white intersecting lines in a sieve-like pattern, white scales, four-dot clods or white rosettes, sticky fiber sign, and peripheral accentuated pigment network with dilated follicles [Figure 2a-h].

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Figure 2:

Dermoscopy revealing (a): White intersecting lines in a sieve-like pattern (yellow circle) and in between red lacunae (black arrow); (b): Hemorrhagic crusts (red arrow), intersecting shiny white structures (yellow arrow), and in between red lacunae (black arrow), four-dot clods or white rosettes (green arrow); (c): Intersecting shiny white structures (black arrow) and in between red lacunae (yellow arrow); (d): Peripheral accentuated pigment network with dilated follicles (yellow circle), white scales (green arrow), and four-dot clods or white rosettes (yellow arrow) with intersecting shiny white structures (red arrow) and in between red lacunae (black arrow); (e): Yellowish crusts (red arrow) with peripheral coppery dots (yellow arrow), red lacunae (green arrow), (f): White intersecting lines in a sieve-like pattern (yellow circle) and in between red lacunae (black arrow) and peripheral accentuated pigment network (red arrow); (g and h): Red lacunae (black arrow) with intersecting white structures (yellow arrow) and peripheral accentuated pigment network (red arrow) (Dermalite DL4, polarized contact mode, 10x).

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Hematological investigations and chest radiographs were normal, and triple serology was non-reactive. Color Doppler of the lower limbs of both patients was normal at the time of the scan. Histopathological examination was suggestive of pseudo-KS [Figure 3a-b]. A final diagnosis of AAD of Mali was made. Both these patients were treated with oral minocycline, topical steroid-antibiotic combinations, and antihistamine. Patients responded well but were lost to follow-up.

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Figure 3:

Histopathological examination revealing (a): lining keratinized stratified squamous epithelium. Dermis showing marked endocapillary proliferation lined by swollen endothelial cells. Minimal inflammation, predominantly chronic, is seen in dermis perivascular distribution (Hematoxylin and eosin 4x); (b): extraverted RBCs and wide areas of hemorrhage and hemosiderin pigment-laden macrophages are seen at the dermo-epidermal interface and deeper dermis (Hematoxylin and eosin 10x).

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AAD or PKS presents in two different forms. The first form, vascular dermatitis or Mali type, usually involves older men with chronic venous insufficiency involving one side of the body and later progresses to the other side, and is characterized by plaque and nodules with ulceration and leaves behind hyperpigmentation on healing. The second variety, Stewart–Bluefarb PKS, usually manifests in infancy and involves only one side of the body. Associated primarily with congenital arteriovenous (AV) malformations and frequently with Klippel–Trenaunay–Weber syndrome, presents with erythema with unilateral purple-blue papules prone to ulceration, venous abnormalities, and soft tissue hypertrophy of limbs.^[2,3] Rare forms include iatrogenic/AV fistula-associated, paralysis associated, status dermatitis-induced, or unclassified. Common dermoscopic features include red/purple lacunae, hemorrhagic crusts, white scales, sticky fiber sign, absence of pigment network, pale background, or vascular lagoons. Table 1 summarizes the differences between PKS and KS.^[3-5]

Although the exact cause is unknown, muscle hypoxia (chronic venous insufficiency or AV shunting) and edema secondary to venous hypertension and calf muscle dysfunction may play a role in neovascularization and cell infiltration.^[2,4] Compression therapy by elastic bandages is the primary treatment. Sclerotherapy, high ligation, valve grafting, vein surgery, reconstruction, and, with success, local corticosteroid, oral antibiotics like erythromycin, and dapsone have been tried.^[2,4,5]

In the current study, clinicians can differentiate between Kaposi sarcoma and pseudo-KS in great detail, which is critical for patient care. In addition, we observed unique dermoscopic features that have rarely been documented in the literature to date. In both cases, the dermoscopic features closely matched the underlying histological findings. Dermoscopy revealed red lacunae (dilated capillary vessels and extravasated erythrocytes), hemorrhagic crusts (superficial ulceration and hemosiderin-laden macrophages), shiny white intersecting lines and rosettes (fibroblast proliferation and skin fibrosis), peripheral coppery dots, and accentuated pigment network (melanin incontinence and hemosiderin deposition in the dermis). White rosettes (keratin-filled adnexal structures) and the sticky fiber sign (spongiosis, transudation-increase in blood pressure, excoriation, or ulceration.^[2,3] Thus, the dermoscopic observations provided a non-invasive clue, which was subsequently verified by histopathology.