Describe the epidemiology.
IgA nephropathy is the most common primary glomerulonephritis in adults.
Peak incidence: second to third decades of life
Sex: ♂ > ♀ (2:1)
Ethnicity: more common in the Asian population (worldwide)
Describe the pathophysiology.
The cause is still not entirely understood.
Most likely mechanism: an increased number of defective, circulating IgA antibodies are synthesized (often triggered by mucosal infections, i.e., upper respiratory tract and gastrointestinal infections) → IgA antibodies form immune complexes that deposit in the kidney → glomerulonephritis (type III hypersensitivity reaction)
List clinical features.
The course of the disease is highly variable and can manifest in the following forms:
Recurring episodes of:
Gross or microscopic hematuria
And/or nephritic syndrome (including hypertension)
Usually during or immediately following a respiratory or gastrointestinal infection 
Can progress to RPGN and/or nephrotic syndrome (< 10% of patients)
Up to 50% of patients progress to end-stage renal disease within 20–25 years.
IgA nephropathy and IgA vasculitis are both IgA-mediated vasculitides triggered by a mucosal infection. IgA vasculitis most commonly occurs in children < 10 years of age and affects multiple organ systems (palpable purpura, abdominal pain, arthralgia). IgA nephropathy is limited to the kidneys and typically affects adults.