NMJ diseases

Question 1

myasthenia gravis

Answer 1

Path: antibodies against muscle nicotinic ach receptor, muscle specific kinase or Lrp4
Sx: fatigable proximal muscle weakness
-involves ocular and bulbar muscles
Dx: tensilon test, antibodies against nAChR, single fiber EMG
Tx: pyridostigmine, steroids, immunosuppressive therapy

Question 2

lambert-eaten myasthenic syndrome

Answer 2

Associated with small cell lung carcinoma
Path: antibodies against the P/Q type voltage gated calcium channel
Sx: fatigable proximal muscles, ocular and bulbar involvement rare, autonomic symptoms

Question 3

duchenne and becker muscular dystrophy

Answer 3

Path: dystrophin gene mutation, xlinked
Sx: childhood onset of proximal muscle weakness including neck flexors; no ocular or bulbar involvement
Dx: CK level elevated
Tx: glucocorticoids

Question 4

Limb-girdle muscular dystrophy

Answer 4

Path: sarcoglycan defects or other proteins
Sx: proximal muscle weakness, no ocular or bulbar weakness
Dx: CK elevated, EMG myopathic

Question 5

myotonic dystrophy

Answer 5

Path: intronic tri/tetra nucleotide repeat expansion
Sx: distal muscle weakness and stiffness, myotonia, systemic features (ptosis, balding)

Question 6

facioscapulohumeral muscular dystrophy

Answer 6

Path: activation of DUX4 gene as a result of contracture
Sx:asymmetric weakness predominantly affecting face, shoulder girdle, upper arms

Question 7

emery dreifuss muscular dystrophy

Answer 7

Path: emerin and lamin A/C gene mutation
Sx: early onset joint contractures; humeroperoneal pattern of muscle food

Question 8

hypokalemic periodic paralysis

Answer 8

Path: skeletal muscle channelopathy (L type)
Sx: generalized weakness lasting hours to days

Question 9

hyperkalemic periodic paralysis

Answer 9

Path: skeletal muscle channelopathy
Sx: episodes of generalized weakness lasting minutes to hours

Question 10

polymyositis and dermatomyositis

Answer 10

Sx: proximal symmetric muscular weakness
DM has purplish discoloration of eyelids (heliotrope) and papular erythematous scaly lesions over knuckles (Gottron patches)
Dx: CK elevated, EMG
Tx: corticosteroids, IVIg for DM

Question 11

inclusion body myositis

Answer 11

weakness asymmetric, prox and distal muscules ie forearm and finger flexors, knee extensors and ankle extensors
Tx: not responsive to steroids