NMJ diseases and scleroderma Flashcards
Describe the frequency and pathophysiology of myasthenia gravis
Most common NMJ disorder
Autoantibodies to postsynaptic ACh receptor
What are the clinical features of myasthenia gravis
Fatigable muscle weakness—ptosis; diplopia; proximal weakness; respiratory muscle involvement (dyspnea); bulbar muscle involvement (dysphagia, difficulty chewing)
Spared reflexes
Worsens w muscle use
What other pathologies is MG associated with
Thymoma, thymic hyperplasia
Tx of MG
AChE inhibitor administration reverses symptoms (pyridostigmine for tx)
Describe the frequency and pathophysiology of Lambert-Eaton myasthenic syndrome
Uncommon
Autoantibodies to presynaptic Ca2+ channel = decreased ACh release
Clinical features of Lambert-Eaton
Proximal muscle weakness, autonomic symptoms (dry mouth, constipation, impotence)
Hyporeflexia
Improves w muscle use
What other pathologies is Lambert-Eaton myasthenic syndrome associated with
Small cell lung cancer
What effect does AChE administration have in Lambert-Eaton myasthenic syndrome have
Minimal
Define Raynaud’s phenomenon and where it commonly occurs
Decreased blood flow to skin due to arteriolar (small vessel) vasospasm in response to cold or stress:
colour change from white (ischemia) to blue (hypoxia) to red (reperfusion)
Most often in fingers & toes
The difference between Raynaud disease & syndrome
Raynaud disease when 1° (idiopathic)
Raynaud syndrome when 2° to a disease process such as mixed connective tissue disease, SLE, or CREST syndrome (limited form of systemic sclerosis)
Digital ulceration (critical ischemia) is seen in 2° Raynaud syndrome
Tx of Raynaud’s
Calcium channel blockers
Define scleroderma
Systemic sclerosis. Triad of autoimmunity, noninflammatory vasculopathy, and collagen deposition with fibrosis. Commonly sclerosis of skin, manifests as puffy, taut skin without wrinkles, fingertip pitting
Involvement of other systems in scleroderma
Renal (scleroderma renal crisis; treat with ACE inhibitors), pulmonary (interstitial fibrosis, pulmonary HTN), GI (decreased peristalsis & LES tone = dysphagia, heartburn), cardiovascular
Who does scleroderma commonly affect
75% females
What are the two types of scleroderma
Diffuse and limited scleroderma
Define diffuse scleroderma
Widespread skin involvement, rapid progression, early visceral involvement
Associated with anti-Scl-70 antibody (anti-DNA topoisomerase-I antibody) and anti-RNA polymerase III
Define limited scleroderma
Limited skin involvement confined to fingers and face
Also with CREST syndrome: Calcinosis cutis, anti-Centromere antibody, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia
More benign course
