Acquired immunodeficiency syndrome (AIDS) is considered to be the most severe stage of human immunodeficiency virus (HIV) infection. It is life-threatening if therapy is not initiated immediately. Patients present with constitutional symptoms of variable severity, wasting, and numerous AIDS-defining illnesses. Clinical and laboratory criteria, especially a very low CD4+T-cell count, are used to make the diagnosis.
Acquired Immunodeficiency Syndrome stems from infectious processes.
AIDS occurs in patients who suffer from a severe and long unrecognized human immunodeficiency virus (HIV) infection (caused by either HIV-1 or HIV-2 virus)   . AIDS is almost never encountered in patients with an acute HIV infection, but rather develops after the period of latency and progressive decrease in CD4+T-cell function  . One of the most important risk factors is the lack of treatment, mostly because of a missed (or unknown) diagnosis. The progressive nature of HIV infection symptoms and infections have been grouped into two diagnostic criteria devised by the Center for Disease Control (CDC) and the World Health Organization (WHO). As per CDC criteria, three distinct categories exist - A, B, and C, with A describing features of acute or asymptomatic HIV infection  . On the other hand, categories B and C (similarly to clinical stages 2,3 and 4 of WHO criteria) include the appearance of AIDS-related conditions. Constitutional symptoms such as fever, fatigue, or diarrhea lasting for at least one month, peripheral neuropathy and numerous infections - Listeriosis, Bacillary angiomatosis, recurrent herpes zoster involving > 1 dermatome and pelvic inflammatory disease (PID) are initial signs of AIDS     . Candidiasis, however, is the most important group B feature of patients with suspected HIV or AIDS and can present in the oropharynx or the genitalia. Additional disorders that belong to the B category are immune thrombocytopenic purpura (ITP), cervical dysplasia (or cervical carcinoma in situ) and oral hairy leukoplakia. When patients present with profound weight loss and poor general condition due to "wasting syndrome" caused by HIV, they are adequately classified into category C and clinical stage 4, respectively, and signs of severe AIDS include     :
Because many disorders are a part of the clinical presentation of AIDS, physicians must maintain a high index of suspicion when any of the mentioned illnesses or infections appear together with a poor general condition. For this reason, a comprehensive workup is necessary to rule out HIV infection and AIDS as a possible cause . Firstly, a detailed patient history must include assessment of potential risk factors such as unprotected sexual intercourse, particularly male homosexual (as the vast majority of patients in the developed world are males belonging to the men having sex with men - MSM population), contact with blood products (through intravenous drug use) or a positive family history in the setting of vertical transmission   . Moreover, the appearance of any of the infections (or their respective signs and symptoms) in recent months should be noted, and a detailed and complete physical examination may confirm cutaneous, pulmonary, or general manifestations of AIDS and warrant a laboratory investigation to diagnose the clinical entity. A neurological exam (including the mini-mental status examination) must be carried out in all patients suspected to have severe HIV infection, in order to assess the extent of neurological involvement and detect AIDS-related dementia. In addition to a complete blood count (CBC), which will show lymphopenia in virtually all patients, an extensive biochemical panel is necessary to evaluate organ status - lipid profile, liver and kidney function, and a full electrolyte panel   . If the diagnosis of HIV is not already known, testing for HIV antibodies is the first step in confirming this infection, followed by a CD4+T-cell count and isolation of viral RNA through polymerase chain reaction (PCR) analysis. Classification of patients harboring an HIV infection, supplementary to clinical criteria, is based on the CD4+T-cell count as well, and a number of < 200/µL is diagnostic for AIDS . Additional recommended procedures include syphilis testing with the Venereal disease research laboratory test (VDRL) and rapid plasma reagin (RPR) tests, detection of anti-toxoplasma antibodies, purified protein derivative (PPD) test for tuberculosis, and determine possible coinfection by hepatitis viruses (A, B, or C)   .