Pathology Notes

Other infections commonly seen in HIV+ patients Updated: 08/17/2025 © Jun Wang, MD, PhD   Mycobacterium avium complex Nontuberculous mycobacteria, M. avium or M. intracellulare More common when CD4+ cell < 50/mcl Associated with shortened survival Incidence decreased due to ART Likely transmitted by inhalation or ingestion Localized lymphadenitis : signs of inflammation, associated with immune reconstitution Disseminated infection o    Presentation: fever, night sweat, diarrhea, etc o    Lab: anemia, elevated LDH and alkaline phosphatase, low CD4 count, etc Pathology findings: aggregates of foamy histiocytes , densely packed acid fast bacilli highlighted by acid fast stain Diagnosis: isolation of pathogen by culture Treatment: antimicrobial, ART Toxoplasmosis Caused by protozoan parasite toxoplasma gondii Most common CNS infection in AIDS Transmitted by ingestion of infectious oocysts from soil or cat litter, or undercooked meat from infected animal...

Cytomegalovirus infections Updated: 08/15/2025 © Jun Wang, MD, PhD   General features AKA Herpes virus type 5 Double stranded DNA virus of Herpes virus family High mortality rate if end-organ involvement: retina, lung, brain 3 patterns of infection o    Latent: most common, immunocompetent patients o    Mononucleosis-like syndrome: immunocompetent patients o    Tissue invasive disease: immunocompromised patients Pathogenesis Inhaled pneumocystis attach to alveolar wall Macrophages could not eradicate pneumocystis due to lack of CD4+ lymphocytes Local inflammation results in alveolar injury Clinical presentations Depending on organ affected Commonly involves esophagus, colon, and retina Pathological features Acute and chronic inflammation, commonly with ulcers Infected cells with large intranuclear inclusions (owl eyes) , or coarse cytoplasmic granules Confirmed by immunohistochemistry studies CMV retinitis Most common ocular complication...

Pneumocystis pneumonia Updated: 08/12/2025 © Jun Wang, MD, PhD   General features Caused by the fungus Pneumocystis jirovecii May occur in any immunocompromised patients, such as those with  primary immunodeficiency One of the most common AIDS defining diseases Likely airborne transmission High mortality and morbidity Pathogenesis Inhaled pneumocystis attach to alveolar wall Macrophages could not eradicate pneumocystis due to lack of CD4+ lymphocytes Local inflammation results in alveolar injury Clinical presentations Chills, fever, nonproductive cough, difficulty breathing, chest pain, fatigue Radiological findings Usually bilateral diffuse infiltrates Pathological features Foamy eosinophilic material in alveolar spaces Silver stain highlights organisms Diagnosis Identification of pneumocystis jirovecii in bronchoalveolar lavage, sputum, or lung biopsy PCR Managements Trimethoprim and sulfamethoxazole     Back to pathology of HIV inf...

Acquired immunodeficiency syndrome (AIDS) Updated: 08/12/2025 © Jun Wang, MD, PhD   General features Definition: CD4+ T cell<200/mcl OR presence of AIDS-defining conditions Advanced HIV infection: CD4+ T cell<50/mcl Usually occurs years after HIV infection  Results of CD4+ T cell depletion Conditions seen in chronic phase can be more severe Poor prognosis associated with late diagnosis or lack of ART AIDS-defined conditions More frequent and severe opportunistic illnesses Results of immunosuppression Basis of presumptive clinical diagnosis for WHO stages 3 and 4 Include opportunistic infections, certain malignancies, and conditions likely associated with uncontrolled HIV infection, such as wasting and encephalopathy Opportunistic infections Pneumocystis pneumonia CMV infections Other infections     Back to pathology of HIV infection Back to contents  

Early HIV infection Updated: 08/12/2025 © Jun Wang, MD, PhD   General features AKA as acute, recent, or primary HIV infection Approximately last 6 months since HIV acquisition Clinical presentations Up to 60% might be asymptomatic Symptoms usually develop in 2-4 weeks Acute retroviral syndrome : fever, lymphadenopathy, sore throat, rash, myalgia/arthralgia, diarrhea, weight loss, and headache Opportunistic infections may occur with CD4 lymphocytopenia Key laboratory findings Rapid viral replication results in high viral load Transient CD4 lymphocytopenia and CD8 lymphocytosis CD4 cell count rebound and CD8 cell decreased after peak of viremia Reversed CD4/CD8 ratio Atypical lymphocytes may present Abnormal liver function, thrombocytopenia and anemia might occur Pathological features Follicular hyperplasia Positive p24 by immunostains Diagnosis Clinical suspicion: symptoms, history of high risk behaviors Detection of HIV antigen, anti-HIV antibodies and/or HIV vir...

HIV-associated complications Updated: 08/10/2025 © Jun Wang, MD, PhD   HIV-associated neurocognitive disorder Associated with neuronal injuries caused by viral components (gp120, gp41, etc) and autoimmune activities Cognitive impairment MRI findings include cortical and subcortical atrophy  Three stages Asymptomatic neurocognitive impairment (ANI) : a score of ≥ 1 standard deviation below the mean in at least two cognitive domains on standardized neuropsychological testing without a symptomatic or observable functional impairment Mild neurocognitive disorder (MND) : a score of ≥ 1 standard deviation below the mean in at least two cognitive domains on standardized neuropsychological testing with at least mild symptomatic or functional impairment HIV-associated dementia (HAD) : a score of ≥ 2 standard deviations below the mean in at least two cognitive domains on standardized neuropsychological testing with concomitant impairment in activities of daily living HIV-ass...

Pathology of HIV infection Updated: 08/07/2025 © Jun Wang, MD, PhD   General features Most commonly caused by HIV-1 HIV-2 infection rare and usually with mild clinical presentations Transmitted through sexual activities, shared intravenous drug equipment, or mother to child (transplacental or milk) Targeting CD4+ cells: T helper, thymocytes, granulocytes, macrophages, Langerhans cells, dendritic cells B cells are also reduced in number and could be dysfunctional  Causes immune dysfunction or hyperactivation Disrupted immune system results in higher risks of infections, especially opportunistic infections, and certain neoplasia (AIDS) Major risk of HIV infection Blood-borne Needle-sharing IV drug usage: High risk Blood transfusion , needle stick, mucosal exposure to blood: usually low risk in America Sexual exposure Key HIV components and their functions Structural o    GP120: binding CD4 o    GP41: Anchoring GP120 to viral envelop, penetrating...