Diagnostic anténatal des reins hyperéchogènes : à propos de 17 cas

Prenatal diagnosis of cystinuria with a heterozygous pathogenic variant in SLC7A9 gene associated with isolated hyperechogenic fetal kidneys: A case report

Cystinuria is suspected antenatally by a hyperechogenic fetal colonic content. We report the first prenatal case of autosomal dominant SLC7A9-related cystinuria associated with isolated hyperechogenic kidneys as the only prenatal sonographic sign.

Fetal hyperechoic kidney cohort study and a meta-analysis

Objective: To investigate the positive rate of chromosomal and monogenic etiologies and pregnancy outcomes in fetuses with hyperechoic kidney, and to provide more information for genetic counseling and prognosis evaluation. Methods: We performed a retrospective analysis of 25 cases of hyperechoic kidney diagnosed prenatal in the Second Affiliated Hospital of Harbin Medical University and Harbin Red Cross Central Hospital (January 2017-December 2022). Furthermore, we conducted a meta-analysis of a series of hyperechoic kidneys (HEK) in the literature to assess the incidence of chromosomal and monogenic etiologies, mortality, and pooled odds ratio (OR) estimates of the association between the incidence of these outcomes and other associated ultrasound abnormalities. Results: 25 fetuses of HEK were enrolled in the cohort study, including 14 with isolated hyperechoic kidney (IHK) and 11 with non-isolated hyperechoic kidney (NIHK). Chromosomal aneuploidies were detected in 4 of 20 patients (20%). The detection rate of pathogenic or suspected pathogenic copy number variations (CNVs) was 29% (4/14) for IHK and 37% (4/11) for NIHK. Whole exome sequencing (WES) was performed in 5 fetuses, and pathogenic genes were detected in all of them. The rate of termination of pregnancy was 56% in HEK. 21 studies including 1,178 fetuses were included in the meta-analysis. No case of abnormal chromosome karyotype or (intrauterine death)IUD was reported in fetuses with IHK. In contrast, the positive rate of karyotype in NIHK was 22% and that in HEK was 20%, with the ORs of 0.28 (95% CI 0.16-0.51) and 0.25, (95% CI 0.14-0.44), respectively. The positive rate of (chromosome microarray analysis) CMA in IHK was 59% and that in NIHK was 32%, with the ORs of 1.46 (95% CI 1.33-1.62) and 0.48 (95% CI, 0.28-0.85), respectively. The positive rate of monogenic etiologies in IHK was 31%, with the OR of 0.80 (95% CI 0.25-2.63). In IHK, the termination rate was 21% and neonatal mortality was 13%, with the ORs of 0.26 (95% CI, 0.17-0.40), 1.72 (95% CI, 1.59-1.86), and that in NIHK was 63%, 0.15 (95% CI, 0.10-0.24); 11%, 0.12 (95% CI, 0.06-0.26), respectively. The intrauterine mortality in NIHK group was 2%, with the OR of 0.02 (95% CI, 0.01-0.05). HNF1B variant has the highest incidence (26%) in IHK. Conclusion: The positive rate of karyotype was 20% in HEK and 22% in NIHK. The positive rate of CMA was 32% in NIHK and 59% in IHK. The positive rate of IHK monogenic etiologies was 31%. HNF1B gene variation is the most common cause of IHK. The overall fetal mortality rate of NIHK is significantly higher than that of IHK. The amount of amniotic fluid, kidney size and the degree of corticomedullary differentiation have a great impact on the prognosis, these indicators should be taken into consideration to guide clinical consultation and decision-making.

Lethal neonatal respiratory failure due to biallelic variants in BBS1 and monoallelic variant in TTC21B

BACKGROUND

Bardet-Biedl syndrome (BBS) is a rare, autosomal recessive ciliopathy characterized by early onset retinal dystrophy, renal anomalies, postaxial polydactyly, and cognitive impairment with considerable phenotypic heterogeneity. BBS results from biallelic pathogenic variants in over 20 genes that encode key proteins required for the assembly or primary ciliary functions of the BBSome, a heterooctameric protein complex critical for homeostasis of primary cilia. While variants in BBS1 are most frequently identified in affected individuals, the renal and pulmonary phenotypes associated with BBS1 variants are reportedly less severe than those seen in affected individuals with pathogenic variants in the other BBS-associated genes.

CASE-DIAGNOSIS

We report an infant with severe renal dysplasia and lethal pulmonary hypoplasia who was homozygous for the most common BBS1 pathogenic variant (c.1169 T > G; p.M390R) and also carried a predicted pathogenic variant in TTC21B (c.1846C > T; p.R616C), a genetic modifier of disease severity of ciliopathies associated with renal dysplasia and pulmonary hypoplasia.

CONCLUSIONS

This report expands the phenotypic spectrum of BBS with the first infant with lethal neonatal respiratory failure associated with biallelic, pathogenic variants in BBS1 and a monoallelic, predicted pathogenic variant in TTC21B. BBS should be considered among the ciliopathies in the differential diagnosis of neonates with renal dysplasia and severe respiratory failure.

Etiologies and outcomes of prenatally diagnosed hyperechogenic kidneys

OBJECTIVES

To determine etiologies and outcomes of fetal hyperechogenic kidneys (HEK).

METHODS

We conducted a retrospective chart review of HEK in British Columbia (January 2013-December 2019) and literature review.

RESULTS

We identified 20 cases of HEK without other anomalies (isolated) in our provincial cohort, one was lost to follow-up. Eight had testable genetic etiologies (autosomal dominant polycystic kidney disease [ADPKD], autosomal recessive polycystic kidney disease [ARPKD], Bardet-Biedl syndrome [BBS], and HNF1B-related disorder). The remaining seven did not have an identifiable genetic etiology. Of cases without a genetic etiology with postnatal follow-up (n = 6) there were no abnormalities of blood pressure, creatinine/estimated glomerular filtration rate or urinalysis identified with follow-up from 2-71 months. We report 11 cases with extrarenal anomalies (nonisolated), with outcomes and etiologies. We identified 224 reported cases of isolated HEK in the literature. A potentially testable genetic etiology was found in 128/224 (57.1%). The neonatal death rate in those with testable etiologies was 17/128 (13.3%) compared to 2/96 (2.1%) when testable etiologies were excluded.

CONCLUSIONS

Genetic etiologies (ARPKD, ADPKD, BBS, HNF1B-related disorder, Beckwith-Wiedemann syndrome, tubular dysgenesis, familial nephroblastoma, and cytogenetic abnormalities) account for approximately half of prenatally isolated HEK; once excluded there are few neonatal deaths and short-term renal outcomes may be normal. There remains a paucity of knowledge about long-term renal outcomes.

Bardet-Biedl syndrome: Antenatal presentation of forty-five fetuses with biallelic pathogenic variants in known Bardet-Biedl syndrome genes

Bardet-Biedl syndrome (BBS) is an emblematic ciliopathy associated with retinal dystrophy, obesity, postaxial polydactyly, learning disabilities, hypogonadism and renal dysfunction. Before birth, enlarged/cystic kidneys as well as polydactyly are the hallmark signs of BBS to consider in absence of familial history. However, these findings are not specific to BBS, raising the problem of differential diagnoses and prognosis. Molecular diagnosis during pregnancies remains a timely challenge for this heterogeneous disease (22 known genes). We report here the largest cohort of BBS fetuses to better characterize the antenatal presentation. Prenatal ultrasound (US) and/or autopsy data from 74 fetuses with putative BBS diagnosis were collected out of which molecular diagnosis was established in 51 cases, mainly in BBS genes (45 cases) following the classical gene distribution, but also in other ciliopathy genes (6 cases). Based on this, an updated diagnostic decision tree is proposed. No genotype/phenotype correlation could be established but postaxial polydactyly (82%) and renal cysts (78%) were the most prevalent symptoms. However, autopsy revealed polydactyly that was missed by prenatal US in 55% of the cases. Polydactyly must be carefully looked for in pregnancies with apparently isolated renal anomalies in fetuses.

Antenatal nephromegaly and propionic acidemia: a case report

BACKGROUND

Propionic acidemia (PA) is a rare but severe recessive autosomal disease, presenting with non specific signs in the first years of life. Prenatal diagnosis is invasive (amniocentesis) and limited to suspect cases. No screening test has been described, in particular no correlations between prenatal sonography and PA have been documented so far.

CASE PRESENTATION

We report the case of a boy with fetal bilateral nephromegaly and hyperechogenic kidneys, along with neonatal acute kidney injury; no etiology could be found in the first months of life. At 3 months of life, he presented with tachypnea and altered mental status, which lead to the diagnosis of PA. The renal ultrasound at 8 months of life, after a symptomatic treatment of PA had been initiated, showed a regression of the renal abnormalities.

CONCLUSION

This case describes PA as a novel cause of large and hyperechogenic kidneys in the antenatal period. It suggests that, when confronted to fetal nephromegaly, hyperechogenic kidneys and risk factors of metabolic disease such as consanguineous parents, PA should be considered, and a prenatal test should be proposed.

Prenatal ultrasound, genotype, and outcome in a large cohort of prenatally affected patients with autosomal-recessive polycystic kidney disease and other hereditary cystic kidney diseases

PURPOSE

To investigate the sonographic and clinical genotype-phenotype correlations in autosomal recessive polycystic kidney disease (ARPKD) and other cystic kidney diseases (CKD) in a large cohort of prenatally detected fetuses with hereditary CKD.

METHODS

We retrospectively studied the clinical and diagnostic data of 398 patients referred with prenatal ultrasound findings suggestive of CKD between 1994 and 2010. Cases with confirmed hereditary CKD (n = 130) were analyzed as to their prenatal ultrasound findings, genotype, and possible predictors of clinical outcome.

RESULTS

ARPKD was most common in our non-representative sample. Truncating PKHD1 mutations led to a significantly reduced neonatal prognosis, with two such mutations being invariably lethal. Sonographically visible kidney cysts occurred in only 3% of ARPKD cases. Renal abnormalities in Meckel syndrome (MKS) appeared earlier than in ADPKD (19.6 ± 3.7 vs. 29.8 ± 5.1 GW) or ARPKD (19.6 ± 3.7 vs. 30.2 ± 1.2 GW). Additional CNS malformations were not found in ARPKD, but were highly sensitive for MKS. Pulmonary hypoplasia, oligo/anhydramnios (OAH), and kidney enlargement were associated with a significantly worse neonatal prognosis.

CONCLUSION

Genotype, sonographic signs of OAH, enlarged kidney size, and pulmonary hypoplasia can be useful predictors of neonatal survival. We propose sonographic morphological criteria for ARPKD, ADPKD, MKS, and renal cyst and diabetes syndrome (RCAD). We further propose a clinical diagnostic algorithm for differentiating cystic kidney diseases.