HIV disease is characterised by depletion and/or dysfunction of the cells of the immune system. HIV infection targets macrophages (which ingest and process infectious agents) and CD4+ T lymphocytes. These cells are central to all functions of the immune system, so that when they are affected by the disease process there is a very extensive immune deficiency.
Up to 80 per cent of people who are infected by HIV will experience a glandular fever-like illness within 6 weeks of infection. This occurs at the time of HIV antibody appearance, and is called a seroconversion illness or primary HIV infection syndrome. Subsequently, there is a period of months to years during which the person is well, even though there is a progressive depletion of CD4+ T lymphocytes and a progressive increase in HIV viral load. Eventually, immune function becomes so poor that opportunistic infections and/or cancers develop. This stage is known as acquired immunodeficiency syndrome (AIDS). The most common cancers are Kaposi's sarcoma and lymphoma. A wide range of pathogens may cause disease in AIDS. Most are viruses such as cytomegalovirus and other herpes viruses, fungi such as Pneumocystis jiroveci, Cryptococcus neoformans and Candida sp. or mycobacteria.
HIV infection may also affect immune system cells in the nervous system and cause neurological diseases. The most common neurological disease is a chronic encephalitis, which may result in a sub-cortical dementia associated with other neurological abnormalities, usually referred to as HIV-associated neurocognitive disorder (HAND).
HIV infection is a progressive condition, which will result in AIDS and death in the majority of infected people if the infection is not treated with antiretroviral therapy. Combination antiretroviral therapy is very effective in arresting the progression of HIV infection. Patients on antiretroviral therapy can enjoy a normal life expectancy but must remain on treatment.
HIV infection should be considered in patients with risk factors, and/or a consistent clinical illness.
Primary HIV infection syndrome
Primary HIV infection syndrome (seroconversion illness) presents a rare opportunity to identify HIV infection, which otherwise may remain unidentified for years. Primary HIV infection syndrome usually occurs within six weeks of infection and may include:
- sore throat
- generalised maculoerythematous rash
- night sweats
- severe lethargy
- mouth ulceration
Neurological manifestations including meningoencephalitis and peripheral neuritis may also be observed.
The acute illness may be accompanied by neutropenia, lymphadenopathy, thrombocytopenia, and mildly elevated erythrocyte sedimentation rate (ESR) or serum transaminase levels.
The role of antiretroviral therapy, in the treatment of primary HIV infection is currently unclear but its use should be considered. This should be discussed with a specialist in HIV medicine as a matter of urgency (see list of contacts in contacts for specialist advice on STIs and HIV).
Sequelae to the acute illness include:
- chronic lethargy
Non-specific viraemic manifestations include:
- mucosal ulceration
- desquamation of skin
- exacerbation of seborrhoea
- recurrence of herpes simplex virus (HSV).