On the methodology for measuring thickness of glomerular basement membranes
Sir,We read with interest the multicentre Italian study by Frascà et al. [1] that confirms that a proportion of patients (6/51) with thin glomerular basement membrane disease (TBMD) have an underlying type IV collagen mutation that may not always be benign.
In the ‘subjects and methods’ section they state that the measurements of glomerular basement membrane was performed by the method published by us [2]. However, our work involved a comparison between the Orthagonal Intercepts Method (OIM) and our modification of direct measurement (MDM) method, applying it on two glomeruli rather than one. Frascà et al. [1] do not state which of the two (or both) methods was used in their study. We found that although the MDM method is acceptable for diagnosing TBMD, on average the values were about 80 nm less than those obtained with OIM. As one of the patients described by Frascà was only 8 years old we would also remind readers that basement membrane thickness is age related [3].
5/18 patients with suggestive family histories or 6/51 in the overall group had collagen IV mutations suggesting that other genes involved in the production or turnover of glomerular basement membrane are likely to be equally important in the pathogenesis of this variant/disease.
It would also be interesting to know if any of the ultrastructural lesions correlated with collagen IV mutations.
Conflict of interest statement. None declared.
1 Histopathology Department Guy's and St Thomas' NHS Foundation Trust2 Department of Renal Medicine Gloucestershire Hospitals NHS Foundation Trust Email: fahim.tungekar{at}kcl.ac.uk
References
- Frascà GM, Onetti-Muda A, Mari F et al. Thin glomerular basement membrane disease: clinical significance of a morphological diagnosis—a collaborative study of the Italian Renal Immunopathology Group. Nephrol Dial Transplant 2005; 20: 545–551
[Abstract/Free Full Text] - Das AK, Pickett TM, Tungekar MF. Glomerular basement membrane thickness–a comparison of two methods of measurement in patients with unexplained haematuria. Nephrol Dial Transplant 1996; 11: 1256–1260
[Abstract/Free Full Text] - Ramage IJ, Howatson AG, McColl JH et al. Glomerular basement membrane thickness in children: a stereologic assessment. Kidney Int 2002; 62: 895–900[CrossRef][Medline]
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