Immunologic Disorders



Immunologic Disorders





ACQUIRED IMMUNODEFICIENCY SYNDROME

Human immunodeficiency virus (HIV) infection is the virus that causes acquired immunodeficiency syndrome (AIDS). Although characterized by gradual destruction of cell-mediated (T-cell) immunity, AIDS also affects humoral immunity and even autoimmunity through the central role of the CD4+ (helper) T lymphocyte in all immune reactions. The resulting immunodeficiency makes the patient susceptible to opportunistic infections, cancers, and other abnormalities that define AIDS.


Causes



  • There are two species of HIV: HIV-1 and HIV-2. HIV-1 is the most common of the two. HIV-1 and HIV-2 retrovirus are transmitted by contact with infected blood or body fluids (semen, breast milk, rectal, or vaginal fluids), although HIV-2 has a slightly lower risk of transmission and typically progresses slower.


High-Risk Populations



  • Homosexual or bisexual men


  • I.V. drug users


  • Neonates of infected women


  • Recipients of contaminated blood or blood products


  • Heterosexual partners of persons in high-risk groups



Clinical Manifestations


Acute Retroviral Syndrome



  • Over 50% of those infected with HIV develop a mononucleosislike syndrome, which may be attributed to flu or another virus and which occurs 1 to 6 weeks post exposure; may remain asymptomatic for years


Latency

During this time period, which can last for a decade or more, the virus is replicating at low levels, but people are often asymptomatic. People who are taking antiretroviral therapy can remain in this phase for decades.


Symptomatic Phase



  • Persistent generalized lymphadenopathy


  • Nonspecific symptoms, including weight loss, fatigue, and night sweats


  • Fevers related to altered function of CD4+ cells, immunodeficiency, and infection of other CD4+ antigen-bearing cells


  • Neurologic symptoms





ALLERGIC RHINITIS

Allergic rhinitis is a reaction to airborne (inhaled) allergens. Depending on the allergen, the resulting rhinitis and conjunctivitis may occur seasonally (hay fever) or year-round (perennial allergic rhinitis). Allergic rhinitis is the most common atopic allergic reaction, affecting over 20 million US residents.



Causes



  • Immunoglobulin (Ig) E-mediated type I hypersensitivity response to an environmental antigen (allergen) in a genetically susceptible person


Common Triggers



  • Wind-borne pollens:



    • Spring — oak, elm, maple, alder, birch, and cottonwood


    • Summer — grasses, sheep sorrel, and English plantain


    • Autumn — ragweed and other weeds


  • Perennial allergens and irritants:



    • Dust mite excreta, fungal spores, and molds


    • Feather pillows


    • Cigarette smoke


    • Animal dander







ANAPHYLAXIS

Anaphylaxis is an acute, potentially life-threatening type I (immediate) hypersensitivity reaction marked by sudden onset of rapidly progressive urticaria (vascular swelling in skin, accompanied by itching) and respiratory distress. With prompt recognition and treatment, prognosis is good. Typically occurring within minutes, the reaction can occur up to 1 hour after reexposure to an antigen.


Causes

Ingestion of or other systemic exposure to sensitizing drugs or other substances, such as:



  • serums (usually horse serum), vaccines, and allergen extracts


  • diagnostic chemicals, such as sulfobromophthalein, sodium dehydrocholate, and radiographic contrast media


  • enzymes such as L-asparaginase in chemotherapeutic regimens


  • hormones such as insulin


  • penicillin or other antibiotic and sulfonamides


  • salicylates


  • food proteins, as in legumes, nuts, berries, seafood, and egg albumin


  • sulfite food additives, common in dried fruits and vegetables and salad bars


  • insect venom


  • nonimmunologic triggers such as cold air or water, heat, exercise, and ethanol

Sep 22, 2018 | Posted by in ANATOMY | Comments Off on Immunologic Disorders
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