Chapter 24 - Cutaneous Manifestations of Microvascular Occlusion Syndromes Flashcards
Antibodies to which antigen cause heparin-induced thrombocytopenia?
Antibodies to complexes of heparin and platelet factor 4
True or false: patients with heparin-induced thrombocytopenia (HIT) will always develop HIT with future heparin exposures.
False; if the patient is exposed to heparin again 100 days or more after the initial episode of HIT, the antibodies necessary to produce this reaction may not be prodcued again, and a second episode of HIT may not occur
Are the platelet plugs that form in heparin-induced thrombocytopenia (HIT) inflammatory or non-inflammatory?
Non-inflammatory
True or false: a normal platelet count excludes the diagnosis of heparin-induced thrombocytopenia (HIT).
False; there is typically a drop in the platelet count, however, sometimes if the pre-heparin platelet count isn’t known, the drop will produced a platelet count that is still within the normal range
Both unfractionated and fractionated heparin can produce heparin-induced thrombocytopenia (HIT). Which type produces HIT more often?
Unfractionated heparin
Why is starting warfarin during an episode of heparin-induced thrombocytopenia (HIT) unwise?
Because thrombosis may be potentiated by a drop in protein C levels (this always occurs when starting warfarin, hence the typical “heparin bridging” used during the first few days of warfarin therapy)
What are the two myeloproliferative disorders that typically produce platelet-induced occlusion of blood vessels?
Essential thrombocythemia and polycythemia vera
What is the name of the condition that’s characterized by burning and paroxysmal erythema of the distal extremities, frequently triggered by skin contact with a warm surface?
Erythromelalgia
*Note: erythromelagia can be primary (idiopathic) or secondary.
Is secondary erythromelalgia more closely associated with essential thrombocythemia or polycythemia vera?
Essential thrombocythemia
What comprises a “white clot” seen on histologic exam within a blood vessel?
Platelets (however, even the most experienced pathologist may have difficulty distinguishing a “white clot” from a fibrin clot)
What type of mutation do 90-95% of patients with polycythemia vera and 50-70% of patients with essential thrombocythemia have?
JAK-2 mutation
What drug can be used to effectively treat the erythromelalgia caused by thrombocythemia?
Aspirin
What’s the name of the condition in which there may be cytopenia of any, or all, blood components, and yet patients have an increased risk of thrombosis due to platelet occulsion? The patients can develop retiform purpura, and they have hemolytic anemia that is Coombs negative.
Paroxysmal nocturnal hemoglobinuria
What does the purpura look like in hemolytic uremic syndrome (HUS)?
There is no purpura; this is a finding associated with full-blown thrombotic thrombocytopenic purpura (TTP) syndrome only
What’s the difference between plasma and serum?
Plasma contains fibrinogen and clotting factors, while serum doesn’t
Will cryofibrinogens be found in serum, plasma, or both?
Cryofibrinogen will only be found in plasma, since serum doesn’t contain any fibrinogen
Will cryoglubulins (immunoglobins that precipitate when exposed to the cold) be found in serum, plasma, or both?
Both
Through what two mechanisms can cryoglubuins cause disease?
Through occlusion or immune complex vasculitis
Name this phenomenon: a clinical presentation that occurs exclusively in leprosy patients from Mexico and Central America, where recurrent crops of large ulcers form on the lower extremities.
Lucio’s phenomenon
Warfarin blue toe syndrome is also known as:
Cholesterol emboli (warfarin, or a different anti-coagulant, gradually lyses the clot overlying a plaque, leaving it subject to the shear stress of arterial flow)
What diagnosis should be considered in a patient with renal failure and a history of recurrent nephrolithiasis, who presents with acute retiform purpura?
Oxalate embolus
What is the term that describes widespread purpura in septic patients?
Purpura fulminans
What population is at greatest risk for post-infectious purpura fulminas?
Children
What two microbes most commonly cause post-infectious purpura fulminans in children (i.e. purpura fulminans two weeks after the onset of the infection)?
Group A streptococcus and VZV infections
What do antibodies bind to in the pathogenesis of heparin necrosis?
Platelet factor 4 + heparin complexes
What alternate anticoagulant agents are options in the setting of heparin necrosis?
LMWH, argatroban, danaparoid, lepirudin
What bloodwork would you order in microvascular occlusion syndromes?
CBCd, smear, PTT, cryoglobulin, LFTs, Cr, BUN, ANCA, skin biopsy
What myeloproliferative disorders are the most likely to cause platelet plugging occlusions?
Essential thrombocythemia, polycythemia vera
What are platelet plugs traditionally referred to as on histology?
“White clot”
What is the mutation in paroxysmal nocturnal hemoglobinuria?
Phosphatidyl inositol glycan class A (PIG-A)
What abN bloodwork would you find in those with TTP?
Thrombocytopenia, microangiopathic hemolytic anemia, renal disease, NORMAL PTT
Describe the 3 types of cryoglobulins.
Type I) monoclonal, IgG, IgM; type II) mixed monoclonal Ab, IgM binds to polyclonal IgG; type III) mixed polyclonal. Both types II and III have RF properties and is known as ‘essential mixed cryolobulinemia’.
What are the difference between Lucio’s phenomenon and erythema nodosum leprosum?
LP has no fever, leukocytosis or tenderness; it also responds poorly to thalidomide and is associated with diffuse lepromatous leprosy
What type of biopsies do you want for query cholesterol embolization?
1) punch bx of retiform purpura 2) elliptical incision around blanched part of livedo reticularis
