Alport Syndrome

I recently saw a patient in clinic with long-standing hematuria with numerous family members on her mother’s side with hematuria.  She now presented with proteinuria but stable renal function.  Collagen IVa disease was highly suspected and genetic sequencing identified a heterozygous carrier for a previously characterized pathogenic mutation in Col4a5.

In the process of taking care of this patient who was heterozygous for X-linked Alport’s syndrome, I wondered, “Who is Dr. Alport?”.

Dr. Arthur Cecil Alport was a physician originally from South Africa who attained his medical training in Edinburgh, Scotland. He had many different interests initially studying malaria abroad and then practicing medicine in London before becoming a Professor in Egypt where he fought for the care of poor patients.  He showed that with careful observation one can provide valuable insights into a specific disease. 

Dr. Alport was not the first to identify the entity of hereditary hemorrhagic nephritis.  Initially, William Howship Dickinson described a family with 11 out of 16 members with albuminuria in 1875.  Subsequent studies by Guthrie and Hurst identified families with hematuria and kidney disease of varying severity.  Dr. Alport saw a patient from the Guthrie/Hurst cohort which he further studied and published with the title, “Hereditary Familial Congenital Haemorrhagic Nephritis”, in the British Medical Journal in 1927 which led to the identification of the disease as Alport’s syndrome. 

In this paper, he found a number of female members of the family had hematuria but did not develop edema, heart failure, and kidney failure, a fate reserved for a selected few male members of the family.  He also noted numerous female members with profound deafness that at time was not associated with hematuria.  Though he acknowledged the hereditary nature of this disease, he also found hematuria and albuminuria were exacerbated by streptococcal infection which he had limited success in recreating in rabbits. 

The history of medicine often provides an interesting context for our current understanding of human disease.  By observing the association of deafness in families with hereditary hematuria, Dr. Alport brought to light a key identifier of the disease entity.  This identification ultimately led to the disease to be associated with his name though the renal phenotype of familial hematuria was discovered by prior investigators.

Posted by Ankit Patel, Nephrology Fellow, Joint BWH/MGH Fellowship Program

Precision Nephrology

One of our attendings, Dr. Sylvia Betcher, PhD, MD gave an excellent presentation at our renal conference about genetic testing in renal diseases that she learned about at #KidneyWeek2015. There were so many good things I liked about her talk, that I want to share what I learned. On January 30th 2015, President Obama announced in his State of the Union address a Precision Medicine initiative. This will provide researchers in the biomedical field with the necessary tools to define preventive measures and treatment of disease by examining variability in genes, environment, and lifestyle of each patient. Precision Medicine relies on specific molecular and genetic information to classify a certain disease into subsets that allow consideration of focused therapies, which is currently being accomplished through GWAS (Check the #NephMadness genetic nephrology region bracket on GWAS here), whole gene sequence analysis via next generation sequencing (NGS) and VAAST (Variant Annotation, Analysis and Search Tool) which is used to identify damaged genes and their disease-causing variants in genome sequences. The president’s 2016 budget will provide $215 million to the various agencies including the NIH and FDA to accomplish his goals. The objectives of such initiative can be found here.

Most of the budget will go to cancer research and there is no mention of rare diseases or any particular hereditary or genetic disease. In the Nephrology world, are there any diseases in particular that need to be addressed? Yes, for instance Steroid Resistance Nephrotic Syndrome (SRNS), among many others. In this paper, a single-gene cause of SRNS was detected in 526 out of 1,783 families (29.5%), by examining 21 genes. The authors mentioned that screening of these genes is cost-effective and may avoid the undesirable side effects of steroids when a mutation is detected and potentially offer targeted therapy (for example with Coenzyme Q10 in cases of COQ2 nephropathy)

According to the NCBI Genetic Testing Registry as of August 2014, there were approximately 4,500 conditions for which genetic testing is available, many of which will have renal manifestations. Advantages to testing include providing specific therapies, allowing family counseling and to evaluate kidney donors in family members. Diseases that are being considered in Nephrology for genetic testing include: rare autosomal dominant interstitial nephropathies (UMOD, MUC1, REN), Syndromic and Polycystic Kidney Disease, Alport Syndrome and Congenital Anomalities of the Kidney and Urinary Tract (CAKUT). Additionally, I want to emphasize the fact that Genomics England (a company owned by the UK Department of Health) and Illumina (an American biotechnology company based in San Diego, California) have launched a $524M project to create a large genome database. Their plan is to sequence 100,000 whole genomes by 2017 focusing on rare diseases, cancer and infectious diseases. A nephrology consortium has been set up to provide renal patients for this ambitious project.

Let’s say we have screened our patients for congenital kidney diseases. Now what? We have to consider whether the results will influence any change in management, or perhaps we need to screen for extra-renal manifestations. I think that providing family counseling will definitively be helpful. It will also influence the decision on safety of kidney donation. Urine could be an excellent source of genetic information through DNA fragmentation which is a normal process in apoptotic cells to eliminate mutated, damaged or infected cells and is usually highly fragmented whereas in cancer cells the DNA maintains its integrity. So in conclusion, these are exciting times in Nephrology with precise genetic testing now a diagnostic option. Do you see yourself practicing Precision Nephrology in 10-20 years? Let us know what you think!

Genetic Defects of the Glomerular Basement Membrane

The glomerular basement membrane is a thin layer of extracellular membrane proteins that is an important part of the filtration barrier, particularly glomerular permselectivity, by preventing proteins from crossing into the filtrate. The major proteins in the GBM are laminin, type IV collagen, nidogen and the heparan sulphate proteoglycan agrin. Interestingly, in the past, I was taught that the highly negative charge on agrin played the major role in mediating charge selectivity. However, recent studies have shown that mutations in the gene encoding agrin, leading to a reduction in charge along the GBM, have no effect of glomerular function in mice. Similarly, deletion of agrin has little effect on permselectivity further suggesting that the role of the proteoglycans in selective filtration is minor at best.

There are two conditions associated with genetic defects in glomerular basement membrane proteins:

Syndrome	Gene(s) affected	Protein	Phenotype
Alports Syndrome	COL4A3 COL4A4 COL4A5	Type IV Collagen, α3, α4, α5 subunits	Initial normal formation of GBM but eventually hematuria, proteinuria and eventual ESRD with characteristic splitting of the GBM. COL4A5 mutations are commonest and are X-linked. Other forms are autosomal.
Pierson Syndrome	LAMB2	Laminin β2	Autosomal recessive disorder with variable phenotype depending on the particular mutation. However, ocular abnormalities (microcoria) are present at birth and the majority of affected individuals progress to ESRD within the first few weeks/months of life. Extrarenal manifestations including hypotonia and neurodevelopmental defects have been reported.

Please see this excellent review in Nature Reviews Nephrology for further information.

Board question: Transplant-1 answer

The vast majority of people answered correctly; the best answer is D.


Approximately 3-5% of patients with Alport's syndrome develop de novo anti-glomerular basement membrane (GBM) disease in the transplanted kidney. Alport’s syndrome is a genetic disorder that results from mutations in the genes encoding the alpha-3, alpha-4, or alpha-5 chains of type IV collagen. Following transplantation, recipients can become alloimmunized and develop antibodies to the normal chains of type IV collagen in the basement membrane of the donor kidney (hence, the linear pattern of staining noted on IF). Treatment is not standardized, but generally consists of plasmapharesis, +/- cyclophosphamide and steroids. Long-term allograft survival is poor and re-transplantation carries a high risk of anti-GBM recurrence. For the boards, remember the post-transplant association between Alport’s syndrome and de novo anti-GBM disease.

Link to NEJM review which contains above picture

Michael Lattanzio DO

Board question of the week: Transplant-1

An 18-year-old white man presents to the renal transplant clinic with complaints of fatigue and nausea for the last week. He was the recipient of a deceased donor kidney transplant 12 months prior and has experienced stable allograft function (Cr 1.2 mg/dL) thereafter. His original renal disease was Alport’s syndrome. His current immunosuppressive regimen consists of tacrolimus and mycophenolate mofetil. He reports strict compliance with this regimen. The nephrologist orders bloodwork:

Bun-50 Cr-5.0 UA-3+ blood 3+ protein dysmorphic RBCs noted
Spot protein/creatinine ratio- 5g/d
C3/C4- normal, FK506 level- 10

Renal transplant ultrasound- no gross abnormality

ANCA pending

Given the worsening renal function, a transplant biopsy is immediately performed. The light microscopy and immunofluorescence appear below:

The answer and explanation will be posted on Monday June 21st

Michael Lattanzio DO

*RFN board questions are meant to help introduce concepts about nephrology related diseases and do not represent actual questions seen on the ABIM exam.

Isolated microscopic hematuria

We have had a rush of patients with isolated hematuria in my clinic recently. The question that occupies so much precious time of the nephrologist reared it's head....... 'what are the indications for a renal biopsy'.

Isolated persistent glomerular hematuria (with dysmorphia) without proteinuria, hypertension or reduced GFR is one of 4 things according to several studies [Caldas et al (1990) Lab Ix; 62:15A. Tiebosch et al (1989) NEJM;320:140]. IgA nephropathy, Alport's Syndrome, Thin Basement Membrane disease or mild glomerulonephritis. Approximately 5% have other diagnoses and a number have a normal biopsy.

Most of these patients have a long term benign course. However many patients with Alport's disease develop progressive renal disease, as do a number of patients with this form of IgA nephropathy. Although thin basement membrane disease is said to be benign, it is not exclusively so and many patient have mutations in Col4a3, Col4a4 genes, similar to Alport patients.

In a pediatric study of Physicians deciding whether to biopsy children for isolated hematuria, only 5% said they would. Further in Pediatric studies where biopsies were performed, only 1 in 39 biopsies for isolated hematuria resulted in a change in management.
It is not always possible from family history to make the diagnosis. However, TBMD is frequently inherited in an AD manner, while Alports syndrome is both autosomal recessive and X-linked (rarely AD). Fewer than 10% of IgA nephropathy patients have an inherited form.

The presence of sterile pyuria might also point to a nephrotoxic cause or a component of interstitial disease and might be taken as a sign of underlying disease activity.


So for patients with isolated persistent hematuria and no clear diagnosis one can either monitor the patients regularly for changes in renal presentation or perform a biopsy.

I would favor performing a renal biopsy only if:

• patient requests for certainty/inform family members/diagnostic curiosity
• Any suggestion from H & P that this might be the early stages of a non-benign disease
• Other atypical features including pyuria.

GBM Collagens & Alport's Syndrome

Alport's Syndrome is a genetic disorder characterized by glomerulonephritis, progression to ESRD, and hearing loss. Intriguingly, it can be inherited in either an X-linked, autosomal recessive, or autosomal dominant manner. Why is the inheritance pattern so complex and what does it tell us about the biology of this interesting disease?

To answer this question we need to understand the composition of the glomerular basement membrane: in addition to being comprised of laminin, nidogen, and sulfated proteoglycans, a major component is collagen IV. There are 6 genes in humans which encode different alpha chains:

COL4A1 encodes alpha-1 collagen (Type IV).

COL4A2 encodes alpha-2 collagen (Type IV).

COL4A3 encodes alpha-3 collagen (Type IV).

COL4A4 encodes alpha-4 collagen (Type IV).

COL4A5 encodes alpha-5 collagen (Type V).

COL4A6 encodes alpha-6 collagen (Type VI).

Three different alpha-chains combine to form a triple helix called a "protomer" which is the fundamental structural unit of the collagen network. The particular collagen protomer which is the major player in the adult kidney is the alpha-3-alpha-4-alpha-5 promoter. Not surprisingly, then, mutations in any one of the three genes can cause Alport Syndrome.

The most common inheritance pattern is X-linked, which accounts for 85% of all cases of Alport Syndrome, and occurs due to mutations in the COL4A5 gene on the X-chromosome.

It is also possible to have autosomal recessive inheritance due to inherited mutations from both patients of either the COL4A3 or COL4A4 genes, both on somatic chromosomes.

Finally, there are rare cases of autosomal dominant inheritance of Alport Syndrome when dominant-negative mutations in either the COL4A3 or COL4A4 genes are inherited.

Acquired GBM Disease

An interesting scenario of "acquired" anti-GBM disease can occur when a patient with Alport's Syndrome gets a renal transplant.

Patients with Alport's Syndrome--a cause of hematuria with progressive renal failure and hearing loss--have mutations in genes encoding certain subunits of the collagen IV molecule which comprises a major structural component of the glomerular basement membrane.

When they undergo a renal transplant, their immune system may well recognize the donor collagen IV as "foreign" since it has never been exposed to this antigen previously, and this can lead to the formation of circulating anti-glomerular basement membrane antibodies and subsequent allograft dysfunction.