Infection with the human immunodeficiency virus (HIV) is the cause of acquired immunodeficiency syndrome (AIDS), and it is a major global health problem. There are 2 virus types, HIV-1 and HIV-2; HIV-1 is the primary cause of infection worldwide. The virus is transmitted primarily by sexual contact but it can also be transmitted parenterally (through injection drug use, through blood transfusion, or at the time of organ transplant) or perinatally (in utero, intrapartum, or during breastfeeding). Men who have sex with men and patients who abuse intravenous (IV) drugs are at increased risk for this infection, as are those with multiple, active sexual partners. The virus attacks CD4 T-lymphocytes, leading to progressive immune dysfunction.

The case definition for HIV infection for adults and adolescents used by the CDC includes 3 stages based on absolute CD4 cells or CD4% (absolute CD4 count is the primarily used metric, with CD4% used in specific situations [such as leukopenia] and in children younger than 5 years):

• Stage 1 for CD4 cells ≥ 500 cells per microliter, or CD4% ≥ 26%.
• Stage 2 for CD4 cells ≥ 200 cells per microliter, or CD4% of 14%-25%.
• Stage 3 (AIDS) with < 200 cells per microliter, or CD4% < 14%, or the presence of an AIDS-defining condition.

Diagnosis of HIV infection is made when a highly sensitive screening test and a highly specific confirmatory test are both positive. There are many approved commercial assays for HIV testing, all with different testing characteristics. Commonly used fourth-generation screening tests combine testing for HIV-specific antibodies and a p24 antigen test. If positive, an assay for differentiation of HIV-1 and HIV-2 is performed, followed by confirmatory testing with the HIV nucleic acid test (NAT).

The clinical manifestations of HIV infection vary widely, from asymptomatic to the varied presentations of different opportunistic infections in the setting of developing immunodeficiency, as well as a variety of inflammation and immune activation-mediated end-organ consequences attributable to the chronic viral infection.

Patients with acute HIV infection may present with signs and symptoms of the acute retroviral syndrome, a mononucleosis-like illness. They may have fever and lymphadenopathy, and in some cases, may have a papular rash and orogenital ulcers. Other symptoms, including sore throat, nausea, vomiting, diarrhea, and headache, may also be present.

Chronic HIV infection may present with a variety of other nonspecific symptoms or signs, and in many cases, is initially asymptomatic. The clinical presentation as infection progresses is protean. Endocrine abnormalities may include hypogonadism, insulin resistance, and lipid abnormalities. Renal dysfunction, myocarditis, and pericarditis may be present.

The skin is involved in up to 90% of people with HIV, and pruritus occurs in up to one-third.  In those with a CD4 count of 200-500 cells, seborrheic dermatitis, zoster, warts, Staphylococcus aureus skin and soft tissue infections, mucocutaneous candidiasis, and oral hairy leukoplakia are common.

As immune function deteriorates, patients may present with one of many AIDS-defining conditions, including multiple or recurrent bacterial infections, bacillary angiomatosis, widespread molluscum contagiosum, candidiasis, disseminated coccidioidomycosis, extrapulmonary cryptococcosis, chronic intestinal cryptosporidiosis, cytomegalovirus-casued retinitis or cutaneous ulcers, ulcerated, hyperkeratotic, or otherwise atypical herpes simplex, disseminated histoplasmosis, chronic intestinal isosporiasis, Kaposi sarcoma, Burkitt lymphoma, primary lymphoma of the brain, disseminated Mycobacterium avium complex or Mycobacterium kansasii infection, Mycobacterium tuberculosis infection, Pneumocystis jirovecii pneumonia, progressive multifocal leukoencephalopathy, recurrent Salmonella septicemia, or toxoplasmosis of the brain. Inflammatory dermatoses such as eosinophilic folliculitis, papulopruritic eruption of HIV, and photodermatitis may also be seen.

Associated malignancies of HIV include lung cancer, Kaposi sarcoma, Hodgkin lymphoma, non-Hodgkin lymphoma,  Merkel cell cancer, cervical cancer, hepatocellular cancer, anal cancer, and mouth cancer (human papillomavirus [HPV] associated; see oral mucosal wart). Higher rates of nonmelanoma skin cancers compared to the general population, such as basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs), are seen.

Related topics: HIV/AIDS-related pruritus, HIV-associated lung disease, papular pruritic eruption of HIV