Myasthenia Gravis

Disorders of the immune system generally fall into three distinct categories based on how the system is failing:

1. Hyperse

   This problem happens because the immune system makes a mistake. Instead of defending the body from germs, it attacks the body’s own tissues.

   • Antibodies: The most common antibody targets the acetylcholine receptor (AChR).
   • MuSK Protein: Some patients have antibodies against the muscle-specific kinase (MuSK), which helps organize AChRs on the muscle cell surface.
   • LRP4: A newer discovered antibody targets lipoprotein-related protein 4.
   • Complement System: The antibodies often activate the complement system, a part of the immune system that further damages the muscle membrane.

   nsitivity (Allergy): The immune system “overreacts” to a harmless substance (allergen), such as pollen, food, or medication, causing damage to the body. This includes conditions like hay fever, asthma, food allergies, and eczema.

2. Autoimmunity: The immune system loses its ability to distinguish “self” from “non-self” and mistakenly attacks the body’s own healthy tissues. This category includes Lupus (SLE), Rheumatoid Arthritis, and Celiac Disease.
3. Immunodeficiency: The immune system is weak, missing parts, or functioning poorly (“underreacting”), leaving the patient vulnerable to severe and recurrent infections.
   • Primary Immunodeficiency (PID): Genetic defects present from birth (e.g., CVID, SCID).
   • Secondary Immunodeficiency: Acquired later in life due to medications (chemotherapy), infections (HIV), or malnutrition.