Alport Syndrome Family Screening and Management: Experience of a Tertiary Center

Abstract

Rationale & Objective

Alport syndrome (AS) is one of the most common causes of inherited chronic kidney disease. Timely diagnosis and treatment of this condition can significantly influence its natural course. The evaluation of at-risk family members allows for the identification of new patients and the initiation of renoprotective measures that help prevent the progression of kidney disease. The aim of this study was to describe the implementation and results of cascade screening among at-risk relatives of a cohort of patients with AS followed at our unit.

Study Design

This is a prospective, single-center study conducted at Nephrology Department, Health Local Unit Gaia/Espinho. We provided patients with letters intended for their first-degree relatives, highlighting the benefits of a referral for renal impairment assessment and genetic counseling. A total of 93 at-risk relatives underwent evaluation through biochemical testing (kidney function and urinalysis abnormalities) and were offered molecular screening for the familial COL4 variant following genetic counseling. Clinical, genetic, and laboratory data were systematically collected.

Observations

Seventy-six (81.7%) at-risk relatives underwent molecular evaluation. A positive molecular test was achieved in 52 (68.4%) relatives, whereas the familial variant was excluded in 24 (31.6%) individuals. 9 (9.6%) individuals declined to proceed with screening and 8 (8.6%) experienced delay in obtaining their results. Among those with a positive molecular screening, 36.5% (n = 19) had urinary protein-creatinine ratio > 0.1 g/g creatinine and 13.5% (n = 7) had glomerular filtration rate (by the CKD-EPI [Chronic Kidney Disease Epidemiology Collaboration] 2021 equation) < 60 mL/min/1.73 m². 30 (57.7%) relatives initiated treatment with a renin-angiotensin-aldosterone system inhibitor. These individuals were older, had higher levels of proteinuria, and had a lower glomerular filtration rate at baseline.

Limitations

The relatively small size of this series from a single unit. The cascade screening based on a patient-led approach may not extent to all the at-risk relatives.

Conclusions

Cascade screening of relatives of patients with AS is an effective strategy for identifying individuals with ongoing kidney disease or those at risk of future renal impairment. This approach enables the early initiation of nephroprotective measures and ensures timely access to appropriate genetic counseling.

Plain-Language Summary

Alport syndrome (AS) is a leading cause of inherited chronic kidney disease. Timely diagnosis and treatment of this condition can significantly influence its natural course. The evaluation of at-risk family members enables the identification of new patients and the early initiation of renoprotective measures to prevent the progression of kidney disease. We implemented a patient-led cascade screening of at-risk relatives of patients with AS. More than half of the evaluated relatives were diagnosed with AS, and most of them started pharmacologic interventions to delay progression of the disease. These findings underscore the importance of cascade screening in identifying individuals with AS and enabling early therapeutic intervention to slow the progression of kidney impairment.

Alport syndrome (AS) is one of the most common causes of inherited chronic kidney disease and the second most common genetic cause of kidney failure.¹ This disorder is caused by deleterious variants on COL4A3, COL4A4, and COL4A5 genes. These genes codify the proteins that form type IV collagen, a key structural component of the glomerular basement membrane, accounting for more than 50% of its composition and essential for normal glomerular filtration barrier function.² The spectrum of kidney damage manifestations is broad, ranging from microscopic hematuria to proteinuria and progressive decline in glomerular filtration rate (GFR), which may ultimately result in kidney failure.^2,3 As type IV collagen is also present in the lens, retinal pigment epithelium, and cochlea, extrarenal manifestations, such as sensorineural deafness and ocular anomalies, can also be observed.⁴ Clinical manifestations depend on the genetic inheritance pattern, which can be X linked, autosomal recessive, autosomal dominant, or digenic.² Today, genetic testing has been recommended to confirm the diagnosis of AS.^5,6

In AS disorders, the risk of developing progressive kidney disease can be delayed or prevented through early initiation of treatment^2,7 with renin-angiotensin-aldosterone system inhibitors (RAASi), especially if initiated before there is any reduction in GFR.^3,8 Currently, treatment is recommended to begin at the time of molecular diagnosis for male patients with X-linked AS, and for men and women with autosomal recessive AS. For women with X-linked AS and for men and women with autosomal dominant AS, RAASi therapy should start at the onset of microalbuminuria (urinary albumin-creatinine ratio > 30 mg/g).^5,9 These facts highlight the importance of identifying at-risk individuals frequently not diagnosed in routine clinical practice, who could benefit from closer monitoring and early intervention. Given that AS is a hereditary disorder, a family-orientated approach for risk assessment of relatives is important.⁶

Index patients and first-degree family members of individuals with AS should receive genetic counseling, independently of inheritance mode.⁵ If a relative has the variant, the process is repeated with their first-degree relatives, and so on. If the variant is not detected, no further subsequent relatives are screened.¹⁰ When screening for a potential at-risk relative is unapproachable, the offspring or subsequent generations of that individual could still be offered screening.¹¹ This process is known as cascade screening.12, 13, 14

Cascade screening in families with monogenic diseases has become standard practice in clinical genetics and genetic counseling for early diagnosis and prevention,¹⁵ especially in early detection of hereditary cancer^12,13 and familial hypercholesterolemia.¹² Nevertheless, cascade screening has recently been described in other hereditary conditions.^10,11

In this study, we described the implementation and the results of a cascade screening of at-risk relatives of a cohort of patients with AS followed at our unit.

Methods

Study Design and Patient Recruitment

We conducted a prospective study from April 2018 to October 2024 at Health Local Unit of Vila Nova de Gaia/Espinho, a tertiary referral hospital in the north of Portugal. This unit provides renal care for a population of ∼600,000 inhabitants. All at-risk relatives provided written informed consent for genetic testing and data collection. This study was conducted with the Ethics Committee of the Health Local Unit of Vila Nova de Gaia/Espinho (CES 152/2021-1).

During the study period, 93 at-risk relatives (from 37 families) were evaluated at our Hereditary Nephropathy Outpatient Clinic. Relatives receiving dialysis or kidney transplantation were not included in this study, because they were not referred to our outpatient clinic. In addition, individuals with insufficient clinical or genetic data were not included in the analysis.

A total of 37 families were evaluated, beginning with index cases with molecularly confirmed AS under follow-up at our unit. Molecular testing was performed using either Sanger sequencing or a next-generation sequencing panel, targeting genes associated with AS. In the study population, 8 distinct deleterious variants were found in the COL4A genes, classified as likely pathogenic or pathogenic according to the American College of Medical Genetics and Genomics guidelines. Regarding COL4A3, the following 3 missense variants were identified: (1) NM_000091.5(COL4A3):c.1219G>C(p.Gly407Arg); (2) NM_000091.5(COL4A3):c.2954G>T(p.Gly985Val); and (3) NM_000091.5(COL4A3):c.898G>A(p.Gly300Arg), along with 1 splice-site variant, NM_000091.5(COL4A3):c.2657-1G>C. For COL4A4, the following 2 variants were found: (1) a missense variant (NM_000092.5(COL4A4):c.3577G>T (p.Gly1193Cys)) and (2) a frameshift variant (c.386delinsCTC p.(Arg1288Serfs∗101)). Regarding COL4A5, 1 missense variant (NM_033380.3(COL4A5):c.3346G>C(p.Gly1116Arg)) and 1 splice-site variant ((NM_033380.3(COL4A5):c.4315+1G>A) were identified. A comprehensive pedigree was performed for each family, and all at-risk relatives were identified and invited to be evaluated through a patient-led approach. Index patients were provided with letters to share with their first-degree relatives, emphasizing the benefits of a referral to our Hereditary Nephropathy Outpatient Clinic for renal impairment assessment and genetic counseling. This approach was selected to uphold the autonomy of patients and their relatives. The screening was initially offered to first-degree relatives. If screening was not feasible or declined, it was subsequently offered to offspring. This procedure was repeated as additional individuals at risk were identified.

Patient demographics, encompassing age and sex, were obtained through interviews and from clinical records, along with relevant laboratory data and medication use. Clinical genetics consultations encompassing genetic counseling were offered to all patients. The genetic tests were ordered to a certified genetics laboratory.

Kidney function was assessed using the estimated GFR, calculated with the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula. In patients younger than 18 years, GFR was estimated using the Swartz formula. Proteinuria was evaluated through the urinary protein-creatinine ratio in the first morning void urine. Proteinuria was considered present when the urinary protein-creatinine ratio exceeded 0.15 g/g. Hematuria was defined as the presence of >3 erythrocytes/high-power field in the urinary sediment.

This study involving human participants was conducted in accordance with the Declaration of Helsinki. Ethics approval was granted by the local Research Ethics Committee. Written informed consent was provided to all participants before genetic testing and data collection.

Aims

The aim of this study was to evaluate the effectiveness of cascade screening in identifying at-risk relatives of patients with AS. In addition, we wanted to assess the impact of this approach on the initiation of renoprotective treatment among relatives diagnosed with AS.

Statistical Analysis

Descriptive statistics were used to summarize categorical variables (expressed as frequencies) and continuous variables (reported as mean, standard deviation, and minimum-maximum values).

To compare clinical and pharmacological characteristics between at-risk relatives diagnosed with AS and those in whom AS was excluded, the χ² test was used to compare categorical variables, whereas for continuous variables, the Mann-Whitney test was used. A P value of <0.05 was considered statistically significant. All statistical analyses were carried out using the IBM SPSS Statistics version 29 software.

Results

A total of 93 at-risk relatives from 37 families were assessed. The mean age was 36.2 years (interquartile range [IQR]: 21.7-50.7; minimum 2 years and maximum 77.2 years) and 56 (60.2%) individuals were women.

In this cohort, a molecular diagnosis was established in 76 (81.7%) relatives. Eight (8.6%) individuals had ongoing biochemical or molecular analyses, as this study was conducted within the framework of clinical practice, in which follow-up appointments may occur at extended intervals. Nine (9.6%) individuals chose not to enroll in the screening, which was as follows: 4 patients declined molecular testing at that time and remain under follow-up, and 5 patients were minors, whose parents chose to postpone testing until they reached adulthood, with continued follow-up in the clinic (Fig 1).

Figure 1.

Flowchart of at-risk relatives identified, tested, and followed up in the study. Abbreviation: AS, Alport syndrome.

The demographic and clinical characteristics of relatives at risk in which a molecular diagnosis of AS was established or excluded (n = 76) are shown in Table 1.

Table 1.

Relatives at Risk Diagnosed With Alport Syndrome and Excluded Alport Syndrome

	Excluded Alport Syndrome (n = 24; 31.6%)	Diagnose Alport Syndrome (n = 52; 68.4%)	P Value
Mean age (y); SD (minimum-maximum)	43.5; 17.9 (2-77)	37.9; 21.2 (4-75)
Median age (y) (IQR)	46.0 (35.5-56.5)	39.5 (18.5-60.5)	0.37
Female, n (%)	14 (58.3)	34 (65.4)	0.74
Median creatinine (IQR)	0.78 (0.64-0.92)	0.81 (0.55-1.03)	0.47
Median eGFR (CKD-EPI) (IQR)	111 (104.1-117.9)	101 (81.5-120.5)	0.08
Median UPCR (IQR)	0.055 (0.04-0.07)	0.16 (0.08-0.40)	<0.001
Signs of renal impairment, n (%)	5 (20.8)	51 (98)	<0.001
Hematuria, n (%)	1 (4.2)	25 (48.1)
Intermittent hematuria, n (%)	3 (12.5)	0 (0)
UPCR > 0.15 < 0.3, n (%)	0 (0)	9 (17.3)
UPCR $\ge$ 0.3 < 1, n (%)	0 (0)	6 (11.5)
UPCR $\ge$ 1, n (%)	0 (0)	4 (7.7)
eGFR < 60 mL/min/1.73 m2, n (%)	1 (4.2)	7 (13.5)
No features, n (%)	19 (79.1)	1 (1.9)
Type inheritance, n (%)
Autosomal dominant	NA	42 (80.8)
Autosomal recessive	NA	0 (0)
X linked	NA	10 (19.2)
Male	NA	2 (3.8)
Female	NA	8 (15.4)

Abbreviations: eGFR (CKD-EPI), estimated glomerular filtration rate using Chronic Kidney Disease Epidemiology Collaboration formula; IQR, interquartile range; NA, not applicable; SD, standard deviation; UPCR, urinary protein-creatinine ratio.

Among the 93 at-risk relatives assessed, 52 tested positive for the familial COL4 variant associated with AS. Of these, 51 (98%) individuals presented with hematuria and 19 (36.5%) of them had concomitant proteinuria. Regarding kidney function, the median estimated GFR was 101 mL/min/1.73 m² (IQR: 81.5-120.5), with 13.5% (n = 7) showing values below 60 mL/min/1.73 m². To better understand the impact of cascade screening on kidney disease progression, it is noteworthy that 30 of the 52 (57.7%) affected relatives started pharmacological renoprotection, with a RAASi, to control proteinuria and/or blood pressure (goal of systolic blood pressure < 120 mm Hg) after nephrological evaluation (Table 2). The patients who started pharmacological renoprotection were older (48.5 years [IQR: 36.5-60.5] vs 20 years [IQR: 7-33]; P < 0.001), had higher levels of proteinuria (median urinary protein-creatinine ratio = 0.39 g/g [IQR: 0.005-0.775] vs 0.10 g/g [IQR: 0.065-0.135]; P < 0.001), and had worse kidney function (median estimated GFR = 90.8 mL/min/1.73 m² [IQR: 71.2-110.5] vs 110.5 mL/min/1.73 m² [IQR: 77.9-110.5]; P = 0.01). Three at-risk relatives were already under renoprotection at the time of their first nephrology consultation.

Table 2.

Impact of Pharmacological Renoprotector Treatment on Relatives at Risk Diagnosed With Alport Syndrome

	Started Pharmocological Renoprotection (n = 30)	Not Started Pharmocological Renoprotection (n = 19)	P Value
Mean age (y); SD (minimum-maximum)	46.2; 17.0 (13-75)	23.47; 17.7 (4-69)	<0.001
Median age (y) (IQR)	48.5 (36.5-60.5)	20 (7-33)	<0.001
Female, n (%)	19 (63.3)	13 (68.4)	0.95
Median creatinine (IQR)	0.95 (0.67-1.23)	0.76 (0.65-0.87)	0.07
Median eGFR (CKD-EPI) (IQR)	90.8 (71.2-110.5)	110.5 (94.2-126.8)	0.01
Median UPCR (IQR)	0.39 (0.005-0.775)	0.10 (0.065-0.135)	<0.001
Signs of renal impairment, n (%)	30 (100)	18 (94.7)	<0.001
Hematuria, n (%)	5 (16.7)	17 (89.5)
Intermittent hematuria, n (%)	0 (0)	1 (5.25)
UPCR > 0.15 < 0.3, n (%)	8 (26.7)	0 (0)
UPCR $\ge$ 0.3 < 1, n (%)	6 (20.0)	0 (0)
UPCR $\ge$ 1, n (%)	4 (13.3)	0 (0)
eGFR (CKD-EPI) < 60 mL/min/1.73 m2, n (%)	7 (23.3)	0 (0)
No features, n (%)	0 (0)	1 (5.25)
ADAS, n (%)	26 (86.7)	14 (73.7)
Female X linked, n (%)	2 (6.65)	5 (26.3)
Male X linked, n (%)	2 (6.65)	0 (0)

Note: n = 52; 3 were already on RAASi.

Abbreviations: ADAS, autosomal dominant Alport syndrome; eGFR (CKD-EPI), estimated glomerular filtration rate using Chronic Kidney Disease Epidemiology Collaboration formula; IQR, interquartile range; RAASi, renin-angiotensin-aldosterone system inhibitor; SD, standard deviation; UPCR, urinary protein-creatinine ratio.

In 24 (25.8%) at-risk relatives, molecular testing ruled out the presence of the familial COL4 variant. In this group, kidney function was generally preserved, with a median estimated GFR of 111 mL/min/1.73 m² (IQR: 104.1-117.9). One exception was a relative diagnosed with chronic kidney disease KDIGO (Kidney Disease: Improving Global Outcomes) G3a A1, likely related to obesity and undergoing treatment with fenofibrate. None of the individuals in this group had proteinuria. However, 4 (16.7%) individuals, all women, presented with intermittent or persistent hematuria and continue to be monitored annually at the clinic.

Discussion

In the era of precision medicine, strategies to improve population health status are prioritized, with growing emphasis on approaches that enable early diagnosis, prevention of disease progression, and personalized treatments.¹² The identification of individuals at risk for hereditary kidney disease through genetic testing represents a key component of precision medicine.¹² After diagnosis, these individuals can be effectively managed to reduce long-term morbidity and mortality.¹² Early intervention with renoprotective therapies (angiotensin-converting enzyme inhibitors and angiotensin receptor blockers) has been shown to delay kidney failure in AS. In the future, other drug classes currently under investigation, including sodium-glucose cotransporter 2 inhibitors, which have demonstrated efficacy in slowing the progression of other kidney diseases, may be incorporated into the therapeutic arsenal.^16,17

Our prospective study demonstrated that systematic familial screening at our unit resulted in a high detection rate of relatives with molecular diagnose of AS. Given the clinical benefits in an early AS diagnosis, namely in improving renal care and preventing disease progression, timely genetic and biochemical screening of at-risk relatives is advisable. In addition, providing genetic counseling to relatives at risk empowers patients regarding life choices, family planning, and living kidney donation.⁶ Moreover, familial screening seems more cost effective than continuous surveillance of all relatives in other circumstances.^18,19 This approach is likely to be especially cost effective in AS, as early RAAS blockade has been shown to significantly improve long-term kidney outcomes. Cost savings arise from delaying or preventing the need for dialysis and transplantation, as well as reduced morbidity and health care use. Although formal cost-effectiveness analyses in AS are limited, current guidelines highlight that early diagnosis and inexpensive RAAS blockade can delay kidney failure, supporting the economic rationale for cascade screening and early intervention.^5,6,20, 21, 22, 23 We recognized that implementing a cascade screening program presents several challenges. These may occur at an individual level (eg, limited understanding or awareness), a relational level (eg, complex family dynamics), or a structural level (eg, limited access to health care services). Such barriers can hinder the effective assessment and management of at-risk relatives.

To address these challenges, health care professionals can adopt strategies such as contacting family physicians to inform them of the hereditary condition and the potential benefit of referring at-risk relatives to a hereditary nephrology clinic. This can be done by written communication—either by mail or email—or by providing index patients with informative letters that they may share with their relatives if they choose to do so.

It is strongly recommended that routine clinical practice includes efforts to inform all at-risk family members and to evaluate those who are willing to undergo assessment. With this article, we aim to share our unit’s experience in identifying and managing individuals at risk of developing kidney disease in the context of a family history of AS. We highlight the importance of providing genetic counseling to relatives of patients with AS, given the relatively high prevalence in Portugal.^24,25 This model could be adopted for the management of other hereditary kidney diseases, as many at-risk relatives with a confirmed risk of developing chronic kidney disease benefited from the early implementation of renoprotective measures. Another important aspect to consider in this type of approach is the need to gather information on patient acceptance and perceived benefit—not only in terms of chronic kidney disease prevention but also regarding the value of receiving targeted genetic counseling based on their specific family situation.