Widespread splitting or lamellation of the GBM is not present, although very localized splitting or lamellation (Figure 3, C) does not rule out TBMN.
44,45) If a biopsy with IgA nephropathy shows true GBM splitting/ lamellation that is not clearly associated with subepithelial and/or subendothelial deposits, we will perform imunofluorescence studies for [[alpha].
The rationale for performing such staining on all cases of suspected TBMN is that heterozygous carriers of X-linked Alport syndrome (Figure 4, B), individuals with autosomal recessive Alport syndrome (Figure 4, C), and even some children with X-linked Alport syndrome (Figure 4, D) may show predominantly thin GBMs with little or no splitting or lamellation by EM.
Ultrastructurally, the GBM presents alternating areas of thinning and thickening, splitting, lamellation, and granular inclusions in the lamina densa.
The GBM of the male patient with AS measured 324 nm and presented typical changes of AS (namely, alternating areas of thin and thick GBM with splitting, lamellation, and granular inclusions).
Any degree of GBM splitting or lamellation is compatible with AS, even if the GBM changes are mild and present over short segments only.