Acetylcholine receptor (AChR) antibody: A protein found in the blood of many people with MG or gMG. The AChR antibody affects signals that are sent from nerves to muscles.

Antibody: A protein that is part of the immune system. When acting normally, antibodies protect you by attacking foreign substances that enter the body such as bacteria and viruses.

Autoimmune disease: Conditions where the immune system mistakenly attacks the body's healthy cells, tissues, and structures.

Chronic: Long-lasting, persistent, or constant. A chronic disease is one with symptoms that occur over a long period of time.

Neonatal Fc receptor (FcRn): An immune system protein that can keep antibodies—including AChR and MuSK—in your system for longer than normal.

Immune system: A system that helps protect your body from infection and disease using specialized cells and organs.

Infusion: A method of delivering medicine to the body. Infusions may be intravenous (into a vein) or subcutaneous (under the skin) and are typically administered by a healthcare professional using an infusion pump to regulate the rate at which the medicine is delivered.

Intravenous (IV): Into a vein. Some infusion treatments are given as intravenous infusions.

Muscle-specific tyrosine kinase (MuSK): A type of antibody that may disrupt communication between nerve and muscle, leading to gMG symptoms. A small number of people with gMG are anti-MuSK antibody positive.

The Myasthenia Gravis Activities of Daily Living (MG-ADL) scale: An 8-category questionnaire that measures how much gMG symptoms affect certain functional activities of daily living, including breathing, talking, chewing, swallowing, actions such as brushing teeth and rising from a chair, as well as double vision and eyelid droop. The score ranges from 0 to 24; a higher MG-ADL score means more severe MG symptoms.

Neuromuscular junction (NMJ): The space where nerves and muscles meet. When the NMJ is damaged or signals between nerve and muscle in the NMJ are interrupted, muscles can grow weaker.

Neurotransmitter: A chemical messenger that carries information from nerve cells, across a space, to other cells. Neurotransmitters help you control your muscles, feel sensations, and respond to your environment.

Receptors: Proteins inside cells, or on their surface, that receive chemical signals.