Clinical Pearls:

• Purpura = red-purple lesions that indicate extravasation of blood into the skin, they do not blanch
  • Purpura can be palpable or non-palpable
  • Purpura can result from abnormalities in 1) Platelets 2) Plasma Coagulation Factors 3) Blood Vessels
  • Non-palpable purpura:  described as petechiae (<3mm) or ecchymoses (>5mm), this is usually non-inflammatory. Causes include abnormal platelet function, DIC, infection, thrombocyptopenia, skin weakness, high intravscular pressure (blood pressure cuffs)
  • Palpable purpura: hallmark sign of leukocytoclastic vasculitis (small vessel vasculitis), occurs due to immune complex deposits in vessel walls, can also be caused by septic emboli
• Cerebral edema is the most common cause of death in fulminant hepatic failure and is related to hyperammonemia
• Dr. Young pointed out that Staphylococcus associated GN is not a classic type of post-infectious GN. As opposed to Strep associated GN which manifests classically manifests weeks after your infection, Staph associated GN often occurs at the same time as your infection. Also it is very important to distinguish HSP from the IgA dominant GN of MRSA infection as the treatments are very different but presentation can be similar. Absolutely don’t treat infection related GN with steroids (See references Below)!
• HCV associated glomerulonephritis can be caused by Type 2 mixed cryoglobulinemia, which is a small vessel vasculitis mediated by antigen-antibody complexes depositing in small blood vessels

References:

• Glassock RJ1 et al. Staphylococcus-related glomerulonephritis and poststreptococcal glomerulonephritis: why defining “post” is important in understanding and treating infection-related glomerulonephritis. Am J Kidney Dis. 2015 Jun;65(6):826-32. doi: 10.1053/j.ajkd.2015.01.023. Epub 2015 Apr 15.
• Satoskar AA et al. Henoch-Schönlein purpura-like presentation in IgA-dominant Staphylococcus infection – associated glomerulonephritis – a diagnostic pitfall. Clin Nephrol. 2013 Apr;79(4):302-12. doi: 10.5414/CN107756.