What is thin membrane nephropathy?
Thin basement membrane nephropathy (TMN; or thin basement membrane nephropathy, TBMN) is an inherited glomerular due to diffuse thinning of the glomerular basement membrane (GBM) from a width of 300 to 400 nm in normal subjects to 150 to 225 nm. It was previously called ‘benign familial haematuria’.
Electron microgram showing comparative thickness of glomerular basement membrane in (a) thin membrane nephropathy; (b) normal kidney; (c) proteinuria due to a chronic glomerulonephritis.
Thin membrane nephropathy is hereditary, and usually transmitted in autosomal dominant fashion. Not all genetic mutations have been characterised. But in some families there is a mutation in the type IV collagen alpha-4 gene.
Who gets it?
It is surprisingly common with a prevalence estimated to be 5-10%. As 10% of the healthy population have asymptomatic microscopic haematuria, this may be in part due to thin membrane nephropathy. It is the cause of microscopic haematuria in 20-25% of patients referred to a nephrologist.
Symptoms
Most patients are asymptomatic and are incidentally noted to have microscopic haematuria on routine urinalysis. Mild proteinuria occasionally occurs, and gross haematuria in 20% of patients.
Kidney function is typically normal, but a few patients develop CKD for unknown reasons. Recurrent flank pain, similar to that in IgA nephropathy, occurs in 30% of patients.
Diagnosis
Diagnosis is based on family history and findings of haematuria without other symptoms or pathology; particularly if asymptomatic family members also have microscopic haematuria. Kidney biopsy is not necessary if there is a family history; but if not, it is often done as part of investigation of haematuria. In other words it is better if at least one family member has a kidney biopsy. After that, unless the case is unusual, not all do need one.
Similarity to Alport Syndrome
Early on, thin basement membrane disease may be difficult to differentiate from Alport syndrome because of histological similarities. This is likely due to the fact that both are caused by abnormalities in Type IV collagen. Genetic analysis can help differentiate these 2 diseases.
Differential diagnosis
Includes Alport Syndome, and IgA Nephropathy.
Treatment
Most patients do not need treatment. And there is no specific treatment for the disease. Patients with frequent gross haematuria, flank pain, or proteinuria may benefit from ACE inhibitors or ARBs, which may lower intraglomerular pressure.
Follow-up and outlook (prognosis)
Because of the small risk of CKD, yearly assessment is advised (U+E, urinary ACR and blood pressure). Long-term prognosis is excellent, and no treatment is necessary in most cases.
Summary
We have described thin membrane nephropathy. We hope it has been useful.
Other resource
Here is more information on thin membrane nephropathy.
Last Reviewed on 19 December 2023