Chapter 226: Aids and Kaposi Sarcoma

PATIENT STORY

A 35-year-old gay man presented with papular lesions on his elbow (Figure 226-1). Shave biopsy revealed Kaposi sarcoma (KS). He subsequently tested positive for HIV infection and began treatment with combination antiretroviral therapy. The KS lesions subsequently went into remission.

INTRODUCTION

In the United States, KS is most often seen in patients with AIDS and in organ transplant patients receiving immunosuppressive therapy. KS can also be classic-type (older Mediterranean men) or endemic-type (young men in sub-Saharan Africa). KS is caused by human herpesvirus 8 (HHV-8), also known as Kaposi sarcoma–associated herpesvirus (KSHV), which evades host immunity and promotes oncogenesis through multiple mechanisms. KS cannot be cured, but treatment can result in disease stabilization or remission. Current therapies aim to restore immune function or target KSHV directly. Therapies that directly target KSHV-mediated oncogenic signaling are being studied.

EPIDEMIOLOGY

• KS can be classic (older Mediterranean men), endemic (young men in sub-Saharan Africa), epidemic (AIDS patients), or organ transplant–associated.¹

• In the United States, 81.6% of KS is seen in patients with AIDS² (see Figure 226-1).

• In HIV-positive patients, the prevalence is 7.2/1000 person years—451 times higher than general population.³

• In transplant patients, the prevalence is 1.4/1000 person years—128 times higher than general population.³

• The male-to-female ratio for epidemic KS in the United States is approximately 50:1 but is falling as the prevalence of AIDS increases among women.⁴ The male-to-female ratio has been approximately 10:1 for classic and endemic KS.

• KS is the most common malignancy seen in AIDS patients, but incidence has been declining at a rate of approximately 6% to 8% per year in the highly active antiretroviral therapy (HAART) era since 2000–2005.

ETIOLOGY AND PATHOPHYSIOLOGY

• KS is caused by KSHV, also known as HHV-8. KSHV is a double-stranded DNA virus that infects numerous cell types throughout the body and expresses oncogenes that interfere with cell cycle regulation and host cell apoptosis.⁵

• KSHV contains a number of genes that allow it to evade host immunity by suppressing the interferon response, inhibiting autophagy, and blocking the natural killer (NK) cell–mediated response.⁶

• The specific mechanisms of viral transmission remain unknown; however, there is evidence implicating salivary shedding and sexual transmission in many cases.⁷

• KS is an angioproliferative neoplasm, demonstrating abnormal proliferation of endothelial cells, myofibroblasts, and monocytes.

• Lesions often begin as papules or patches and progress to plaques as proliferation continues. Some lesions ulcerate (nodular stage), and lymphedema can occur.

RISK FACTORS

• HHV-8 infection.

• Immunodeficiency or immunosuppression (particularly ...