From the Guidelines
Thin Basement Membrane Nephropathy (TBMD) is a benign familial hematuria condition, also known as benign familial hematuria, characterized by autosomal dominant inheritance and typically negative family history of renal failure.
Key Characteristics
- Usually autosomal dominant inheritance 1
- Gross hematuria in less than 10% of patients 1
- Positive family history of hematuria 1
- Typically negative family history of renal failure 1
Diagnosis and Differentiation
TBMD must be distinguished from IgA nephropathy and Alport syndrome 1. Renal biopsy may be difficult to differentiate histologically from early Alport syndrome 1.
Clinical Implications
Individuals with TBMD may proceed with kidney donation if IgA nephropathy or Alport syndrome is excluded, and they are older than 40 years 1. However, prospective donors must be counseled that slowly progressive renal insufficiency may occur, and long-term donor risk remains unknown 1.
Screening and Evaluation
Screening family members' urine may be useful in the setting of persistent unexplained microhematuria, as TBMD has been described as an autosomal dominant condition 1. Renal biopsy diagnosis requires light microscopy, immunofluorescence, and electron microscopy to diagnose TBMD and other glomerular diseases 1.
From the Research
Definition and Characteristics of Thin Basement Membrane Nephropathy (TBMD)
- Thin Basement Membrane Nephropathy (TBMD) is a nephropathy defined by diffuse thinning of the glomerular basement membrane (GBM) at electron microscopy examination, without the alterations of Alport's syndrome (ATS) 2.
- It is characterized by isolated hematuria, with or without minimal proteinuria, and is usually regarded as a benign cause of hematuria with no significant effect on renal function 3, 4.
- However, some studies suggest that TBMD may not always be benign, and in some cases, progressive renal insufficiency may develop, especially in patients with associated proteinuria 3, 2.
Clinical Features and Prognosis
- The clinical course of TBMD is usually benign, with most affected individuals having minimal proteinuria, normal renal function, and a uniformly thinned GBM 5.
- However, some adults with TBMD may have proteinuria >500 mg/day or renal impairment, which may be due to secondary focal segmental glomerulosclerosis (FSGS) or immunoglobulin A (IgA) glomerulonephritis 5.
- The prognosis of TBMD is generally good, but patients with associated glomerulopathies, such as FSGS or IgA nephropathy, may have a poorer outcome 4, 6.
Diagnosis and Differentiation from Other Conditions
- TBMD is diagnosed by electron microscopic examination of renal biopsy tissue, which shows diffuse thinning of the GBM 3, 2.
- Differentiation between TBMD and other conditions, such as IgA glomerulonephritis, can be challenging and may require renal biopsy 6.
- However, in patients with isolated microscopic hematuria and a positive family history of TBMD, renal biopsy may not be necessary 6.