This lecture was conducted during the Nephrology Unit Grand Ground by Medical Student rotated under Nephrology Division under the supervision and administration of Prof. Jamal Al Wakeel, Head of Nephrology Unit, Department of Medicine and Dr. Abdulkareem Al Suwaida, Chairman of the Department of Medicine. Nephrology Division is not responsible for the content of the presentation for it is intended for learning and /or education purpose only.

MYASTHENIA GRAVIS Presented by: Fayez Al Rogi Medical Student February 2009

DEFINITION Chronic autoimmune neuromuscular disease. It is a disorder of neuromuscular function thought to be due to the presence of antibodies to acetylcholine receptors at the neuromuscular junction.

PREVALENCE Prevalence of 50,000 cases in US. All ethnic groups and both genders. Female to male ratio – 20 to 40 years (females 1.5:1) – 50 to 70 years (males 1.5:1)

IMMUNOPATHOLOGY Autoantibody (antagonistic) for acetylcholine receptor at post-synaptic neuromuscular junction. The nerve cell conveys its message to tell the muscle to contract. The antibodies interfere with the message and the muscle contracts less efficiently. Resulting in the weakness of the arms or legs or of the muscles of the head.

Acetylcholine receptors are – Blocked – Altered – Destroyed

75% of patients have thymus abnormality: – 85% thymic hyperplasia – 15% thyroma – Disease usually more severe with thymus abnormality.

ETIOLOGY The cause is unkown.

CLINICAL FEATURES Drooping of the eyelids ( Drooping of the eyelids (Ptosis). Double vision. Double vision. Facial muscles weakness. Difficulty in swallowing (dysphagia). Difficulty in swallowing (dysphagia). Weakness of arms, hands, fingers, legs. Difficulty breathing if chest muscle are affected. Difficulty breathing if chest muscle are affected.

DiplopiaPtosis

Exacerbation of MG Emotional stress Pregnancy Menses Secondary illness Trauma Temperature extremes Hypokalemia Drugs – aminoglycosides antibiotics, beta blockers, procainamide, quinidine, phentoin, and some psychotropic drugs

DIAGNOSIS OF MG History. Physical examinations for muscle fatigue. Edrophonium Test. EMG. Lab Dx. CT of thymus gland.

 Edrophonium Test (Tensilon) – IV administration of Edrophonium chloride – Blocks degradation of acetylcholine – Brief relief of eye weakness

Laboratory Dx  Acetylcholine receptor antibody (Anti-AChR) Acetylcholine receptor antibody, binding – 90% generalized – 70% ocular Acetylcholine receptor antibody, blocking – 50% generalized – 20% ocular Acetylcholine receptor antibody, modulating – 90% generalized – 70% ocular

 Muscle-specific tyrosine kinase antibody – Anti-MuSK – 45% of seronegative MG

TREATMENT Anticholinesterase agents – Neostigmine (Prostigmin) – Pyridostigmine (Mestinon) Corticosteroids / Immunosuppressive agents – Prednisone – Azathioprine Intravenous Immunoglobulin (IVIG) Thymectomy Plasmapheresis (plasma exchange)

LIFESTYLES A person with Myasthenia Gravis can lead a normal life if the medications are taken in the correct dosages and at the right time of the day.

THANK YOU