Epidemiology

Mainly children < 5 years of age

Etiology

Bacterial exotoxins
- Shiga-like toxin (verotoxin)
  - From enterohemorrhagic E. coli (EHEC) strain O157:H7
  - Usually transmitted via contaminated foods (e.g., undercooked beef or raw leafy vegetables)
- Shiga toxin produced by Shigella dysenteriae
Streptococcus pneumoniae infection

HUS is a thrombotic microangiopathy, a condition characterized by the formation of microthrombi occluding the microvasculature.

Infection with enterohemorrhagic E. coli (EHEC) or another causative organism
Mucosal inflammation facilitates bacterial toxins entering systemic circulation.
- Most commonly Shiga-like toxin from enterohemorrhagic E. coli (EHEC) strain O157:H7
Toxins cause endothelial cell damage (especially in the glomerulus ).
Damaged endothelial cells secrete cytokines that promote vasoconstriction and platelet microthrombus formation at the site of damage (intravascular coagulopathy) → thrombocytopenia (consumption of platelets)
RBCs are mechanically destroyed as they pass through the platelet microthrombi occluding small blood vessels (i.e., arterioles, capillaries) → hemolysis (schistocytes), and end-organ ischemia and damage, especially in the kidneys → decreased glomerular filtration rate (GFR)