1. A mild form of Alport syndrome: Hereditary nephropathy in the absence of extra-renal features
Yoon H-S, Wilson JC & Eccles MR Pathology, University of Otago, Dunedin, New Zealand

2. Alport syndrome (AS)
A hereditary disorder resulting from abnormal type IV collagen
Nephropathy with considerable genetic and clinical heterogeneity characterized by haematuria, proteinuria and progressive renal failure, first reported by Alport in 1927
Frequently associated with:
Eye abnormalities
High tone sensorineural deafness
Rarely associated with:
Mental retardation
Leiomyomatois

3. Alport syndrome: genetics
85% of AS patients: X-linked inheritance of mutations in the COL4A5 gene on Xq22 encoding the a5(IV) collagen chain
COL4A5 is a large gene comprising 51 exons
As many as 609 mutations have been described to date and are spread throughout the gene without any hot spots (Arup Laboratory 2011)
15%: Autosomal inheritance of mutations of the COL4A3 or COL4A4 gene encoding the a3(IV) or a4(IV) on 2q36-37:
14%: autosomal recessive
1%: autosomal dominant

4. Type IV collagen formation7S
Collagenous
NC1 a1
a1a1a2 a2 a3
a3a4a5 a4 a5
a5a5a6 a6
a(VI) chain
Protomer
Meshwork formation
Hudson et al, NEJM 348:2543, 2003

5. Type IV collagen distribution
a1.a1.a2(IV): Ubiquitously present in basement membrane (BM) in many tissue
a3.a4.a5(IV) and a5.a5.a6(IV): Restricted tissue distribution
In the kidney a1.a1.a2(IV) network predominates during early nephrogenesis in GBM.
During the 2nd trimester of foetal development, a3.a4.a5(IV) network gradually becomes dominant
a3.a4.a5(IV) is also expressed in the eye, cochlea, lung and testis while a5.a5.a6(IV) network is present in skin, oesophagus and smooth muscle.

6. Initial presentation of the NZ family
Two sisters (IV6:58 yo and IV8:54 yo) presented to the clinic to be considered as potential live kidney donors for their sons (V29:27 yo and V35:33 yo, respectively) who had ESRF.
Both women were found to have significant proteinuria (1.8, 1.4g/d, respectively) and hypertension and they proceeded to a renal biopsy (mild mesangial proliferation and hypertensive arteriosclerosis).
Routine questioning revealed a strong familial history of hypertension and the possibility of a familial form of renal disease.
Subsequent clinical review of the family identified a number of additional family members with renal disease.
Negative for hearing loss or eye abnormalities in all individuals tested.

7. 1. Subjects with renal disease identified before DNA tests
Identif-ication number
Age (yrs old) Gender
Presentation
Renal Function and Blood Pressure
Biopsy
Inheritance
III2 F
Died on dialysis
Not done
Affected/ Carrier
IV3
57 M
ESRF. Dialysis
Renal
Transplant at 41
Affected
IV5 46 M
Proteinuria
Hypertension
Chronic kidney disease
V24 39
Haematuria
Normal renal function
Mild mesangial matrix expansion
V29 27
Acute nephritic syndrome
2nd renal transplant at 26
Chronic glomerulo-nephritis
V31 36
BP 136/86
Mesangial cell proliferation
V35 33
ESRF and renal transplant at 28
IV39 72
Proteinuria 1.6g/24 hr
No haematuria
Mild chronic kidney disease
BP 144/76
V42
Proteinuria 1.1g/24 hr
BP 126/80
Identif-ication number
Age(yrs old) Gender
Presentation
Renal Function and Blood Pressure
Biopsy
Inheritance
IV26 58 F
Proteinuria 1.8g/24 hr Hypertension
BP 152/76
Mesangial cell proliferation
Hypertensive arteriosclerosis
Carrier
IV28 54
Proteinuria
1.4g/24 hr Hypertension
Normal renal function
Mesangial cell proliferation Hypertensive arteriosclerosis
Dead:1, ESRF:3, Chronic disease:3

8. Histology of V42

10. IHC for a3, a4 and a5(IV) a3 a4 a5
Abs gift from Dr Sado

11. Diagnostic dilemma Is this Alport syndrome?
No hearing or eye abnormalities
Mild form of kidney disease and late onset
11 Glomerulonephritis
4 ESRF (3 males and 1 female)
Low penetrance!!
A new entity of hereditary kidney disease?

12. Extended family pedigree
A total of 155 family members for 6 generations examined (81M and 74F).
Black symbols: Biopsy confirmed GN (6M).
Gray symbols: Clinically GN, biopsy not done (4M & 1F).
Black dots: Obligate carriers (21F).
White symbols: No clinical disease (71M & 73F).
Cross: Confirmed by DNA testing.
Predominance of GN in males and lack of male to male transmission
consistent with X-linked inheritance

13. Family pedigree (simplified)
X-chromosome
microsatellite marker

14. Two point LOD scores between the GN locus and markers mapping to chromosome Xq21.33-23
Theta
0.01
0.05
0.1
0.2
0.3
0.4
DXS6809
-infinity
-0.31
0.88
1.21
1.25
0.99
0.57
DXS6789
3.14
3.08
2.86
2.58
1.98
1.35
0.69
DXS8096
3.59
3.53
3.28
2.96
2.28
1.56
0.8
DXS1210
DXS6749
-0.61
-0.01
0.16
0.13
The linked region encompassing COL4A5

15. Nucleotide sequence alteration in COL4A5 in affected family members
G>A substitution at nucleotide 4913 in Exon 50 (asterisk)
Resulting in Cys1638Tyr
Mae III digest of exon
50 PCR products
A allele
Present in all affected
family members and not in 192 healthy control
M NC Affected males Affected & carrier females

16. 1.Renal disease identified before DNA tests
2.Renal disease/carriers identified after DNA tests
Identif-ication number
Age (yrs old) Gender
Presentation
Renal Function and Blood Pressure
Biopsy
Inheritance
III2 F
Died on dialysis
Not done
Affected/ Carrier
IV3
57 M
ESRF. Dialysis
Renal
Transplant at 41
Affected
IV5 46 M
Proteinuria
Hypertension
Chronic kidney disease
V24 39
Haematuria
Normal renal function
Mild mesangial matrix expansion
V29 27
Acute nephritic syndrome
2nd renal transplant at 26
Chronic glomerulo-nephritis
V31 36
BP 136/86
Mesangial cell proliferation
V35 33
ESRF and renal transplant at 28
IV39 72
Proteinuria 1.6g/24 hr
No haematuria
Mild chronic kidney disease
BP 144/76
V42
Proteinuria 1.1g/24 hr
BP 126/80
Identif-ication number
Age(yrs old) Gender
Presentation
Renal Function and Blood Pressure
Biopsy
Inheritance
IV24 69 F
Trace microscopic haematuria
Normal renal function
BP 168/86
Not done
Carrier
IV26 58
Proteinuria 1.8g/24 hr Hypertension
BP 152/76
Mesangial cell proliferation
Hypertensive arteriosclerosis
IV28 54
Proteinuria
1.4g/24 hr Hypertension
Mesangial cell proliferation Hypertensive arteriosclerosis
IV31
Hypertension Negative urine
IV34 65
IV36 61
Microscopic haematuria
V40 38
Haematuria
BP 118/60
Mild mesangial cell proliferation
IV47
Negative urine
BP 148/70
V44 36
Intermittent microscopic haematuria
BP 120/76
V49 43
BP 120/70
V37 39

17. Depiction of NC1 domain showing locations of cysteine sequence alterations and clinical details of patients

18. Summary
We report a unique cysteine to tyrosine substitution in the NC1 domain of COL4A5 in a New Zealand family who presented with a phenotypically mild form of Alport syndrome, suggesting that in this family substitution of Cys1638Tyr led to late onset renal failure without hearing loss or eye abnormalities.

19. Histology of female carriers (IV26)6B

20. EM (carrier IV26)
150nm

21. EM (carriers IV26)

22. Summary
Thin basement membrane nephropathy could be seen in some carrier women containing COL4A5 mutations.