Pseudokaposi's sarcoma.

Sir,

Pseudo-Kaposi's sarcoma, also known as Acroangiodermatitis of Mali is a rare skin disease that can mimic Kaposi's sarcoma both clinically and histopathologically.

We present a case of pseudo-Kaposi's sarcoma without clinical evidence of venous insufficiency but later detected by Doppler studies, and responded well to treatment with dapsone. The histological features were characteristic.

A 23-year-old man presented with a nonhealing raised and exudative lesion of one year duration on the lateral aspect of the right leg. It started spontaneously as a small ulcer without any history of trauma and progressed for about 2 months to reach the present size [Figure 1]. The patient did not have pain or other symptoms.

Figure 1

Hyperpigmented plaque on the lateral aspect of right leg showing papular excrescences

On examination, there was a single hyperpigmented, ill-defined plaque of 15 × 10 cm size on the lateral aspect of right leg. The surface was studded with small papular excrescences. The surrounding skin was normal.

General and systemic examinations did not reveal any abnormalities. Differential diagnosis of Kaposi's sarcoma and chromoblastomycosis were considered. Complete blood count, abdominal ultrasonography, and chest radiography were normal.

Mantoux test was negative. Enzyme-linked immunosorbent assay for human immunodeficiency virus was nonreactive. Skin biopsy showed moderate irregular epidermal hyperplasia with a thick compact orthokeratotic horny layer. The papillary dermis was markedly thickened and showed proliferation of numerous thick-walled capillaries along with numerous siderophages containing golden yellow refractile hemosiderin. No granulomas were found [Figure 2].

Figure 2

(a) 4× view showing dermal thickening and hemosiderin deposits; (b) 10× view showing epidermal thickening, dilated blood vessels, and hemosiderin deposits; (c) 40× view showing hemosiderin deposits.

Based on these findings, a provisional diagnosis of pseudo-Kaposi's sarcoma was made. Venous Doppler of the same limb showed right great saphenous vein varicosities with incompetent saphenofemoral junction and perforators at three sites without evidence of superficial or deep vein thrombosis. Immunotyping with CD34 showed positivity in the endothelial cells but negativity in the surrounding parenchyma, which ruled out Kaposi's sarcoma and was consistent with the diagnosis of pseudo-Kaposi's sarcoma [Figure 3].

Figure 3

10× view (immunohistochemistry) showing CD34 positivity in the dilated blood vessels

He was put on oral dapsone 100 mg once daily, topical nadifloxacin and was advised to use compression stockings. The patient was irregular in using compression stockings but took oral dapsone regularly as advised, without any adverse effects. He showed a remarkable improvement in three months period in the form of disappearance of papular excrescences and flattening of lesions [Figure 4].

Figure 4

Lesion showing flattening with disappearance of papules following treatment

Acroangiodermatitis encompasses a spectrum of benign angioproliferative disorders characterized by proliferation of pre-existing vasculature first described by Kopf and Gonzalez in 1964.[1] It was Mali et al., in 1965, who described its clinical manifestations in 18 patients who also had associated chronic venous insufficiency.[2] Subsequently, similar clinical presentation was described in young patients with congenital arteriovenous (AV) malformations (Stewart–Bluefarb syndrome),[3] in patients with amputated or paralyzed extremities,[4] and with acquired iatrogenic arteriovenous fistulae.

Clinically, it presents as purplish blue macules and nodules commonly on the lower extremities. The pathogenetic mechanism involved is thought to be due to chronic venous stasis leading to tissue hypoxia resulting in neovascularization and fibroblast proliferation.[56]

The condition mimics Kaposi's sarcoma both clinically and histopathologically with the common features being dermal fibrosis, red blood cell extravasation, and hemosiderin deposition.[7] The differentiating features are that in Kaposi's sarcoma, vascular proliferation is independent of the existing vessels and there is presence of slit-like spaces and spindle cell proliferation, whereas in pseudo-Kaposi's sarcoma, small dilated vessels are seen lined by plump endothelial cells with hyperplasia of pre-existing vasculature.[78]

CD34 staining also helps to differentiate between the two. In pseudo-Kaposi's sarcoma, positivity is seen on endothelial cells of hyperplastic vessels, whereas in Kaposi's sarcoma, positivity is seen on both endothelial cells and the characteristic spindle-shaped, perivascular cells.[3]

Various modalities of treatment have been described. The most important is the correction of the underlying pathology with compression stockings and surgery for varicose veins. Other treatment modalities tried with good response are topical steroid therapy,[9] oral erythromycin,[9] and dapsone.[8] Our case also showed a good response to oral dapsone. The exact mechanism by which dapsone and erythromycin act is not known. Erythromycin appears to have anti-inflammatory effect and has been shown to inhibit the chemotaxis of leukocytes, monocytes, and eosinophils.[10]