Lekcja 7: Kliniczne aspekty chorób układu odpornościowego 2 | Clinical Aspects of Immune System Diseases 2

Allergic Diseases

Allergic diseases arise when the immune system overreacts to harmless substances like pollen, food, or pet dander. These substances, known as allergens, trigger an exaggerated immune response, leading to a range of symptoms depending on the system affected.

Common Allergic Diseases

  1. Allergic Rhinitis (Hay Fever): Caused by allergens such as pollen or dust mites, allergic rhinitis is characterized by sneezing, nasal congestion, and itchy, watery eyes.
  2. Asthma: A chronic inflammatory disease of the airways, asthma is triggered by allergens, irritants, or exercise. Symptoms include wheezing, breathlessness, and coughing.
  3. Atopic Dermatitis (Eczema): A chronic skin condition where the skin becomes inflamed, red, and itchy, often triggered by allergens or irritants.
  4. Food Allergies: Certain foods (e.g., peanuts, shellfish) can trigger an immune response that may lead to symptoms ranging from mild hives to severe anaphylaxis, which is a life-threatening condition.

Etiology and Risk Factors

  • Genetics: A family history of allergies significantly increases the risk.
  • Environmental Triggers: Exposure to allergens like pollen, dust, or pollution can increase susceptibility.
  • Immune System Imbalance: Allergies often arise from an overproduction of immunoglobulin E (IgE), which activates mast cells and basophils.

Pathophysiology

Allergic diseases are driven by type I hypersensitivity. When an allergen enters the body, IgE antibodies bind to it and trigger mast cells to release histamine and other inflammatory mediators. This process leads to the hallmark symptoms of allergy, such as swelling, itching, and bronchoconstriction.

Clinical Manifestations

  • Allergic Rhinitis: Sneezing, nasal congestion, runny nose, itchy eyes.
  • Asthma: Difficulty breathing, chest tightness, wheezing, coughing.
  • Atopic Dermatitis: Red, inflamed skin, intense itching, dry patches.
  • Food Allergies: Hives, swelling, gastrointestinal discomfort, and in severe cases, anaphylaxis (rapid-onset respiratory distress and shock).

Diagnostic Approach

  • Skin Prick Test: Used to identify specific allergens by introducing small amounts of allergens into the skin and observing for a reaction.
  • Serum IgE Levels: Elevated IgE levels suggest an allergic response.
  • Pulmonary Function Tests (for Asthma): Used to assess lung function and airflow limitation.

Treatment

  • Antihistamines: Block the effects of histamine, reducing symptoms like sneezing and itching.
  • Corticosteroids: Used to reduce inflammation, especially in asthma and severe allergic rhinitis.
  • Immunotherapy (Allergy Shots): Gradual exposure to allergens to desensitize the immune system over time.
  • Epinephrine (for Anaphylaxis): Administered during severe allergic reactions to counteract life-threatening symptoms.

Immunodeficiency Disorders

Immunodeficiency disorders occur when the immune system is unable to mount an adequate response to infections. These disorders can be primary (genetic and present from birth) or secondary (acquired later in life due to other factors like infections or medications).


Primary Immunodeficiency Disorders

Primary immunodeficiencies are usually genetic and result in either a lack or malfunction of immune cells. These disorders can affect B cells, T cells, or both, making the individual susceptible to frequent and severe infections.

Severe Combined Immunodeficiency (SCID)

SCID is a rare but serious disorder where both T cells and B cells are defective or absent, leading to severe immunodeficiency. Children with SCID often suffer from life-threatening infections within the first few months of life.

  • Etiology: Genetic mutations affecting T cell and B cell development.
  • Clinical Manifestations: Recurrent infections (e.g., pneumonia, meningitis), chronic diarrhea, failure to thrive.
  • Diagnostic Approach: Newborn screening for T-cell receptor excision circles (TREC), flow cytometry to assess T and B cell function.
  • Treatment: Bone marrow transplantation is the most effective treatment for restoring immune function.

Common Variable Immunodeficiency (CVID)

CVID is the most common symptomatic primary immunodeficiency, characterized by low levels of immunoglobulins, leading to recurrent bacterial infections, particularly of the respiratory and gastrointestinal tracts.

  • Etiology: Genetic and environmental factors that affect B cell differentiation and immunoglobulin production.
  • Clinical Manifestations: Frequent sinus infections, pneumonia, gastrointestinal infections, and a higher risk of autoimmune diseases.
  • Diagnostic Approach: Measurement of serum immunoglobulin levels (IgG, IgA, IgM) and testing B cell function.
  • Treatment: Immunoglobulin replacement therapy is the standard treatment, alongside antibiotics to prevent or treat infections.

Secondary Immunodeficiency Disorders

Secondary immunodeficiencies arise due to external factors that suppress or weaken the immune system.

Acquired Immunodeficiency Syndrome (AIDS)

AIDS is caused by the human immunodeficiency virus (HIV), which primarily attacks CD4+ T cells, a vital component of the immune system. As the virus destroys these cells, the body becomes more susceptible to infections and certain cancers.

  • Etiology: Infection with HIV, a retrovirus transmitted through blood, sexual contact, or from mother to child during childbirth.
  • Clinical Manifestations: Early HIV infection may present with flu-like symptoms. As the infection progresses to AIDS, patients develop opportunistic infections (e.g., Pneumocystis pneumonia, tuberculosis) and certain cancers (e.g., Kaposi’s sarcoma).
  • Diagnostic Approach: HIV antibody tests, CD4+ T-cell count, viral load testing to measure the amount of HIV in the blood.
  • Treatment: Antiretroviral therapy (ART) is the mainstay of treatment, helping to suppress the virus and restore immune function.

Iatrogenic Immunodeficiency

This type of immunodeficiency occurs when the immune system is weakened by medications such as corticosteroids, chemotherapy, or immunosuppressants (often used in organ transplantation or autoimmune diseases).

  • Etiology: The use of drugs that intentionally suppress the immune system to prevent organ rejection or control autoimmune diseases.
  • Clinical Manifestations: Increased susceptibility to infections, such as fungal, viral, or bacterial infections.
  • Diagnostic Approach: Blood tests to monitor immune cell counts, including T and B cells, and regular screening for infections.
  • Treatment: Adjusting or discontinuing immunosuppressive therapy when appropriate, alongside prophylactic antibiotics to prevent infections.