Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (555 page)

   Imaging and genetic studies establish the diagnosis.

THIN BASEMENT MEMBRANE NEPHROPATHY (BENIGN FAMILIAL HEMATURIA)

   Definition

   This relatively common familial disorder affects approximately 1% of the general population and is considered, along with IgA nephropathy and Alport syndrome, a common cause of hematuria in children and adults.

   In addition to hematuria, patients with thin basement membrane nephropathy (TBMN) have uniformly thinned glomerular basement membrane as determined be electron microscopy.

   The genetic defect is similar to that of hereditary nephritis (Alport syndrome). Approximately 40% of patients with TBMN have heterozygous mutations at the
COL4A3/COL4A4
locus and thus can be considered carriers of autosomal recessive Alport syndrome.

   Prognosis is benign and hematuria clears spontaneously with time.

   Who Should Be Suspected?

Possible candidates are patients with a family history of hematuria (noted in 30–50% of patients). Macroscopic hematuria can happen and may be associated with flank pain but without evidence of renal disease.

   Laboratory Findings

   Laboratory diagnosis is directed to exclude other glomerular disorders that may cause isolated hematuria, such as IgA nephropathy and Alport syndrome.

   Urinalysis: microscopic hematuria can be persistent or intermittent and is usually asymptomatic. Urinary dysmorphic RBCs and RBC casts may present.

   Renal function and urinary protein excretion are frequently normal.

   Diagnosis requires the demonstration of diffusely thin GBMs by electron microscopy. If these are found, it is necessary to rule out Alport syndrome by immunohistologic and genetic studies.

Suggested Reading

Haas M. Alport syndrome and thin glomerular basement membrane nephropathy: a practical approach to diagnosis.
Arch Pathol Lab Med.
2009;133(2):224–232.