49 Myasthenia Gravis

Question 1

Thymic tumors occur in what percentage?

Answer 1

10-15%

Question 2

Usual sites of metastasis of thymomas

Answer 2

Lungs and Liver

Question 3

Histologic characteristic of thymoma

Answer 3

Hyperplasia of the medulla characterized by lymphoid follicles with active germinal centers (p1475)

Question 4

A second period of danger in progressive caes is from what year of onset?

Answer 4

4-7yrs of onset

Question 5

Grading Classification of MG

Answer 5

Osserman

Question 6

Most frequently affected trunk muscle in MG

Answer 6

Erector spinae

Question 7

Prevalence of MG

Answer 7

43-84 per million persons (Epidemiology p.1473)

Question 8

Peak age of first symptoms

Answer 8

20-30 women, 50-60 men

Question 9

The main ultrastrucrural alterations occur in the?

Answer 9

Motor endplate

Question 10

Changes in the motor endplate

Answer 10

Simplification in the surface area of the postsynaptic membrane (sparse,shallow, abnormally wide or absent synaptic cleft) and a widening of the synaptic cleft

Question 11

Defect in myasthenia gravis?

Answer 11

Marked reduction in the number of ACh receptors of the postsyanptic membrane of the NMJ

Question 12

Rapid reduction in the amplitude of compound muscle action potentials during a series of repetitive stimulation of a peripheral nerve at a rate of 3 per second

Answer 12

Decrementing response

Question 13

Technique that demonstrated an inconstancy of the normally invariant interval between the firing of muscle fibers connected to the same motor unit

Answer 13

Single fiber EMG

Question 14

A nonneoplastic lymphofollicular hyperplasia of the thymic medulla occurs in

Answer 14

65%

Question 15

anticholinesterase inhibitors

Answer 15

Neostigmine

Endrophonium

Question 16

This enzyme plays a role in supporting the normal structure of the postsynaptic membrane and in the arrangement of AChR but its main function may be in developmental synaptic differentiation.

Answer 16

IgG antibodies against intracellular muscle specific kinase (MuSK)

Question 17

There is an increased representation of these Haplotypes in MG

Answer 17

HLA-B8 and DR3 (p1474)

Question 18

Onset before age 40,no thymoma-female.

which antigens are involved?

Answer 18

HLA A1, B8, DRW3 Antigens (p1464)

Question 19

onset after 40, no thymoma- male preponderance

which antigens are involved?

Answer 19

HLA A3, B7, DRW2, Low AChR ani body titer