Ftl. Van Der Loop et al., Identification of COL4A5 defects in Alport's syndrome by immunohistochemistry of skin, KIDNEY INT, 55(4), 1999, pp. 1217-1224
Backgronnd. The COL4A3-COL4A4-COL4A5 network in the glomerular basement mem
brane is affected in the inherited renal disorder Alport's syndrome (AS). A
pproximately 85% of the AS patients are expected to carry a mutation in the
X-chromosomal COL4A5 gene and 15% in the autosomal COL4A3 and COL4A4 genes
. The COL4A5 chain is also present in the epidermal basement membrane (EBM)
. It is predicted that approximately 70% of the COL4A5 mutations prevent in
corporation of this chain in basement membranes.
Methods. We investigated whether or not COL4A5 defects could be detected by
immunohistochemical analysis of the EBM. Punch skin biopsies were obtained
from 22 patients out of 17 families and two biopsy specimens from healthy
males were used as controls.
Results. In four cases with the COL4A5 frameshift or missense mutations, th
e COL4A5 chain was either lacking from the EBM (male) or showed a focally n
egative pattern (female). In three other patients with a COL4A5 missense mu
tation, a COL4A3 and a COL4A4 mutation, respectively, the COL4A5 staining w
as normal. A (focally) negative EBM-COL4A5 staining was found in three pati
ents of six families with a diagnosis of AS and in one family of a group of
four families with possible AS. Conclusions. The (focal) absence of COL4A5
in the EBM of skin biopsy specimens can be used for fast identification of
COL4A5 defects. Combined with polymorphic COL4A5 markers, both postnatal a
nd prenatal DNA diagnosis are possible in the family of the patient.