MRI: Cerebral<unk>  with primary involvement in the right occipital lobe (at left and below of the image). 48-year-old woman with AIDS. Diagnosis of<unk>  in humans is made by biological, serological, histological, or molecular methods, or by some combination of the above.<unk>  can be difficult to distinguish from primary central nervous system lymphoma. It mimics several other infectious diseases so clinical signs are non-specific and are not sufficiently characteristic for a definite diagnosis. As a result, the possibility of an alternate diagnosis is supported by a failed trial of antimicrobial therapy (pyrimethamine, sulfadiazine, and folinic acid (USAN: leucovorin)), i.e., if the drugs produce no effect clinically and no improvement on repeat imaging. T. gondii may also be detected in blood, amniotic fluid, or cerebrospinal fluid by using polymerase chain reaction. T. gondii may exist in a host as an inactive cyst that would likely evade detection. Serological testing can detect T. gondii antibodies in blood serum, using methods including the Sabin–Feldman dye test (DT), the indirect hemagglutination assay, the indirect fluorescent antibody assay (IFA), the direct agglutination test, the latex agglutination test (LAT), the enzyme-linked immunosorbent assay (ELISA), and the immunosorbent agglutination assay test (IAAT). The most commonly used tests to measure IgG antibody are the DT, the ELISA, the IFA, and the modified direct agglutination test. IgG antibodies usually appear within a week or two of infection, peak within one to two months, then decline at various rates.<unk> plasma IgG antibodies generally persist for life, and therefore may be present in the bloodstream as a result of either current or previous infection. To some extent, acute<unk>  infections can be differentiated from chronic infections using an IgG avidity test, which is a variation on the ELISA. In the first response to infection,<unk> plasma-specific IgG has a low affinity for the<unk> plasma antigen; in the following weeks and month, IgG affinity for the antigen increases. Based on the IgG avidity test, if the IgG in the infected individual has a high affinity, it means that the infection began three to five months before testing. This is particularly useful in congenital infection, where pregnancy status and gestational age at time of infection determines treatment. In contrast to IgG, IgM antibodies can be used to detect acute infection but generally not chronic infection. The IgM antibodies appear sooner after infection than the IgG antibodies and disappear faster than IgG antibodies after recovery. In most cases, T. gondii-specific IgM antibodies can first be detected approximately a week after acquiring primary infection and decrease within one to six months; 25% of those infected are negative for T. gondii-specific IgM within seven months. However, IgM may be detectable months or years after infection, during the chronic phase, and false positives for acute infection are possible. The most commonly used tests for the measurement of IgM antibody are double-sandwich IgM-ELISA, the IFA test, and the immunosorbent agglutination assay (IgM-ISAGA). Commercial test kits often have low specificity, and the reported results are frequently misinterpreted. In 2021, twenty commercial anti-Toxoplasma IgG assays were evaluated in a systematic review, in comparison with an accepted reference method. Most of them were enzyme-immunoassays, followed by agglutination tests, immunochromatographic tests, and a Western-Blot assay. The mean sensitivity of IgG assays ranged from 89.7% to 100% for standard titers and from 13.4% to 99.2% for low IgG titers. A few studies pointed out the ability of some methods, especially WB to detect IgG early after primary infection. The specificity of IgG assays was generally high, ranging from 91.3% to 100%; and higher than 99% for most EIA assays. The positive predictive value (PPV) was not a discriminant indicator among methods, whereas significant disparities (87.5%–100%) were reported among negative predictive values (NPV), a key-parameter assessing the ability to definitively rule out a<unk> plasma infection in patients at-risk for opportunistic infections. Congenital Recommendations for the diagnosis of congenital<unk>  include: prenatal diagnosis based on testing of amniotic fluid and ultrasound examinations; neonatal diagnosis based on molecular testing of placenta and cord blood and comparative mother-child serologic tests and a clinical examination at birth; and early childhood diagnosis based on neurologic and ophthalmologic examinations and a serologic survey during the first year of life. During pregnancy, serological testing is recommended at three week intervals. Even though diagnosis of<unk>  heavily relies on serological detection of specific anti-Toxoplasma immunoglobulin, serological testing has limitations. For example, it may fail to detect the active phase of T. gondii infection because the specific anti-Toxoplasma IgG or IgM may not be produced until after several weeks of infection. As a result, a pregnant woman might test negative during the active phase of T. gondii infection leading to undetected and therefore untreated congenital<unk> . Also, the test may not detect T. gondii infections in immunocompromised patients because the titers of specific anti-Toxoplasma IgG or IgM may not rise in this type of patient. Many PCR-based techniques have been developed to diagnose<unk>  using clinical specimens that include amniotic fluid, blood, cerebrospinal fluid, and tissue biopsy. The most sensitive PCR-based technique is nested PCR, followed by hybridization of PCR products. The major downside to these techniques is that they are time-consuming and do not provide quantitative data. Real-time PCR is useful in pathogen detection, gene expression and regulation, and allelic discrimination. This PCR technique utilizes the 5' nuclease activity of Taq DNA polymerase to cleave a nonextendible, fluorescence-labeled hybridization probe during the extension phase of PCR. A second fluorescent dye, e.g., 6-carboxy-tetramethyl-rhodamine, quenches the fluorescence of the intact probe. The nuclease cleavage of the hybridization probe during the PCR releases the effect of quenching resulting in an increase of fluorescence proportional to the amount of PCR product, which can be monitored by a sequence detector.<unk>  cannot be detected with immunostaining. Lymph nodes affected by<unk> plasma have characteristic changes, including poorly demarcated reactive germinal centers, clusters of monocytoid B cells, and scattered epithelioid histiocytes. The classic triad of congenital<unk>  includes: chorioretinitis, hydrocephalus, and intracranial arteriosclerosis. Other consequences include sensorineural deafness, seizures, and intellectual disability. Congenital<unk>  may also impact a child's hearing. Up to 30% of newborns have some degree of sensorineural hearing loss. The child's communication skills may also be affected. A study published in 2010 looked at 106 patients, all of whom received<unk>  treatment prior to 2.5 months. Of this group, 26.4% presented with language disorders.
Toxoplasmosis
Histoplasmosis
African histoplasmosis
Zygomycosis
Botryomycosis
Ehrlichiosis
Chromoblastomycosis
Talaromycosis