Type IV collagen immunostaining patterns in Alport syndrome and thin basement membrane nephropathy

Disease	Alpha-3 chain	Alpha-4 chain	Alpha-5 chain
Alport syndrome
X-linked inheritance – males	Absent*	Absent*	Absent*
X-linked inheritance – females	Patchy*	Patchy*	Patchy*
Autosomal recessive inheritance	Absent*	Absent*	Absent in GBM, present in basement membranes of Bowman's capsule and the distal tubule*
Autosomal dominant inheritance	Present	Present	Present
Thin basement membrane nephropathy^¶	Present	Present	Present

Type IV collagen immunostaining is a useful adjunct to routine evaluation of kidney biopsy samples from patients with isolated glomerular hematuria, particularly when a specific diagnosis is not provided by routine immunofluorescence and electron microscopy. Abnormal type IV collagen immunostaining is highly suggestive of Alport syndrome. It is important to note that thin GBMs and normal type IV collagen immunostaining may be observed in patients with hemizygous and heterozygous mutations in COL4A5, heterozygous mutations in COL4A3 and COL4A4, and mutations in both alleles of COL4A3 and COL4A4 and may be associated with progressive renal disease. Except as noted, the present/absent designation in the table refers to GBM staining only.

GBM: glomerular basement membrane.
* Up to 20% of male patients and 30 to 40% of female patients with X-linked Alport syndrome may exhibit positive staining for the alpha-3, alpha-4, and alpha-5 chains of type IV collagen. Some patients with autosomal recessive Alport syndrome have normal type IV collagen immunostaining.
¶ Some clinicians (including the authors of the associated topic) consider patients who have thin GBMs and a COL4A3 or COL4A4 mutation to have autosomal dominant Alport syndrome.

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Type IV collagen immunostaining patterns in Alport syndrome and thin basement membrane nephropathy