IgA Vasculitis (Henoch-Schönlein purpura) : Pathogenesis and clinical findings
Authors: Mia Koegler Nela Cosic Reviewers: Crystal Liu Yan Yu* Martin Atkinson* * MD at time of publication
Infectious Agents
50% have preceding upper respiratory tract infections, i.e., influenza virus or Group A Strep
Drugs
I.e., antibiotics (penicillin, erythromycin), NSAIDs and biologics (tumor necrosis factor α inhibitors)
Immunogenetic and cellular predisposition
Various genetic polymorphisms alter cell- mediated immune response, IgA levels elevated in 50% of people
↑ Circulating galactose-deficient IgA1 (GD-IgA1). Deficiency in galactosylation of IgAà↓ IgA serum clearanceàadhesion of IgA complexes, which then deposit into the endothelial lining of blood vesselsàattraction of various inflammatory cells to the area:
Formation of Secretion of Interleukin 8 (IL8) – cytokine that induces Neutrophils infiltrate Activation of complement immune complexes neutrophilic chemotaxis and macrophage phagocytosis the tissue site factors (C3, C4)
Leukocytoclastic vasculitis (histopathologic term for small vessels inflamed by neutrophilic autoimmune response)
Inflamed cutaneous vessels become enlarged in clusters
Symmetrical palpable purpura (red/purple, non- blanchable papules) distributed on lower limbs and buttocks areas
Cutaneous small vessel vasculitis (100%)
Inflamed gastric vessels – hemorrhage and edema within bowel wall
Gastrointestinal (85%)
Colicky abdominal pain (commonly in the periumbilical region), nausea, vomiting
Gastrointestinal
GI bleeding (hematemesis, melena), Intussusception
Glomerular mesangial proliferation and inflammation
↑ mast cell deposition in joints
Joints (60-85%)
Arthralgia’s (common), arthritis (especially knees and ankles)
Arthralgia often transient. No permanent sequelae
Sympathetic nervous system activation
Glomerulosclerosis, tubulointerstitial and podocyte damage
Renal tissue ischemia
↑ Na sensitivity in renal tubules (↑ Na and water retention)
Renal (10-50%)
Increased renin secretion
HTN, nephrotic/nephritic syndrome, renal insufficiency
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published September 1, 2019 on www.thecalgaryguide.com