IgA NEPHROPATHY



PRIMARY IgA NEPHROPATHY (aka "Berger's disease")

I. Pathophysiology and epidemiology
  1. An idiopathic proliferative nephritis affecting the mesangial region of glomeruli
  2. More common in individuals of European or Native American descent than in those of African descent
  3. Males > females
  4. Seen in both children and adults; Peak incidence is in 2nd-3rd decades
  5. Asymptomatic IgA deposition is found on renal biopsy in 3-16% of healthy patients
  6. Risk factors for progression to renal failure (there is no established predictive algorithm, however):
    1. Persistent proteinuria > 1g/d (most predictive)
    2. Male gender
    3. Older age at onset
    4. Sustained hypertension
    5. Impaired renal function
    6. Nephrotic syndrome
II. Diagnosis and clinical features
  1. Gold standard is renal biopsy (immunofluorescence microscopy shows IgA deposition; typically no glomerulosclerosis until late in course)
  2. Clinical features:
    1. Ranges from benign to rapidly progressive renal failure
    2. Incidence of end-stage renal disease is 20-40% over 15-30y (lower with onset in childhood)
    3. Can cause flank pain
    4. About 30% of patients present with microscopic hematuria, often persisting over years without diagnosis
    5. About 40% of patients present with macroscopic hematuria (often with "tea-colored" urine) concurrently with an upper respiratory infection
    6. About 20% of patients present with azotemia
    7. < 10% of patients present with nephrotic syndrome
    8. 10-20% of cases will spontaneously remit
  3. Differential diagnosis
    1. Henoch-Schonlein purpura (a systemic form of IgA nephropathy; acute onset, self-limited, seen primarily in children; in addition to renal involvement can have mono-arthritis, abdominal pain from bowel ischemia, and palpable purpura but normal platelet count;  renal bx findings similar to IgA nephropathy; 5% develop end-stage renal disease)
    2. Thin glomerular basement membrane disease (aka "benign familiar hematuria'-benign, children are most commonly affected, causes microscopic hematuria)
III. Management of patients with suspected but unconfirmed primary IgA nephropathy (i.e. persistent, isolated microscopic hematuria)
  1. Q6-12mo checks of BP, BUN/Cr, urine protein:creatinine ratio, urinalysis
  2. Decision to do renal biopsy-Generally based on presence of an indication of progression, e.g.:
    1. Hypertension
    2. Declining renal function
    3. Proteinuria > 1g/d
IV. Management of patients with confirmed primary IgA nephropathy
  1. ACE inhibitors
    1. Reduce proteinuria and BP in patients with primary IgA nephropathy and renal insufficiency, hypertension, or proteinuria > 500mg/d
    2. Unclear benefit in other patients
  2. Corticosteroids or other immunosuppressants-Typically used with proteinuria > 1g/d despite use of ACE inhibitor
  3. Fish oil-Conflicting results from clinical trials
  4. Tonsillectomy if presents with tonsillitis (see above)-Little evidence to support as of 2012
  5. Renal transplantation if end-stage, but up to 50% of transplant recipients will develop IgA nephropathy of the transplanted kidney

Secondary IgA NEPHROPATHY

Causes include:
(Sources include Core Content Review of Family Medicine, 2012)