Diagnosis of Immunoglobulin A (IgA) Nephropathy
Urinalysis

Sometimes renal biopsy

Diagnosis is suggested by any of the following:

Gross hematuria, particularly within 2 days of a febrile mucosal illness or with flank pain

Incidentally noted findings on urinalysis

Occasionally, rapidly progressive GN

When manifestations are moderate or severe, diagnosis is confirmed by biopsy.

Urinalysis demonstrates microscopic hematuria, usually with dysmorphic RBCs and occasionally RBC casts. Mild proteinuria (< 1 g/day) is typical and may occur without hematuria; nephrotic syndrome develops in ≤ 20%. Serum creatinine level is usually normal.

IgA Nephropathy (Mesangial IgA Deposition) IgA Nephropathy (Mesangial IgA Deposition) IgA Nephropathy (Mesangial IgA Deposition)

Image provided by Agnes Fogo, MD and the American Journal of Kidney Disease’s

Atlas of Renal Pathology (see www.ajkd.org).

IgA Nephropathy (Mesangial Expansion) IgA Nephropathy (Mesangial Expansion)

IgA Nephropathy (Mesangial Expansion)

Image provided by Agnes Fogo, MD and the American Journal of Kidney Disease’s Atlas of Renal Pathology (see www.ajkd.org).

Renal biopsy shows granular deposition of IgA and complement (C3) on immunofluorescent staining in an expanded mesangium with foci of segmental proliferative or necrotizing lesions. Importantly, mesangial IgA deposits are nonspecific and also occur in many other disorders, including immunoglobulin A–associated vasculitis, cirrhosis, inflammatory bowel disease, celiac disease, psoriasis, HIV infection, lung cancer, and several connective tissue disorders.

Glomerular IgA deposition is a primary feature of immunoglobulin A–associated vasculitis, and it may be indistinguishable from IgA nephropathy based on biopsy specimens, leading to speculation that immunoglobulin A–associated vasculitis may be a systemic form of IgA nephropathy. However, immunoglobulin A–associated vasculitis is clinically distinct from IgA nephropathy, usually manifesting as hematuria, purpuric rash, arthralgias, and abdominal pain.

Other serum immunologic tests are usually unnecessary. Complement concentrations are usually normal. Plasma IgA concentration may be elevated, and circulating IgA-fibronectin complexes are present; however, these findings are not helpful diagnostically.