Cost-effective genotyping for classical congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) in resource-poor settings: multiplex ligation probe amplification (MLPA) with/without sequential next-generation sequencing (NGS)

PURPOSE

Genotyping of classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is becoming increasingly significant beyond prenatal counseling in the current era of emerging gene therapy/editing technologies. While the knowledge of common variants helps in designing cost-effective genotyping strategies, limited data are currently available from the Indian subcontinent, especially South India, mainly due to financial constraints. The aim of this study is to assess the genotype of individuals with classic CAH from a South Indian cohort in a cost-effective manner.

METHODS

The genotypes of 46 unrelated subjects with classic CAH were studied through initial multiplex ligation-dependent probe amplification (MLPA) using the SALSA MLPA Probe-mix P050 CAH (MRC Holland). Next-generation sequencing (NGS) was done in 10 subjects, as their MLPA was either negative or showed heterozygous variants.

RESULTS

The common variants observed in our study population of 46 subjects were large deletions (35.8%), intron 2 variant [c.293-13A/C > G] (35.8%), 8 bp del [c.332_339del p.(Gly111Valfs*21)] (7.7%), and R356W [c.1069 C > T p.(Arg357Trp)] (6.6%). MLPA alone detected pathogenic variants in 78.2% of the initial study samples (36/46). Sequential NGS resulted in a 100% detection rate in our study population.

CONCLUSION

MLPA appears to be an effective first genotyping modality for this South Indian cohort due to the high prevalence of large deletions and common variants. MLPA as a first initial screening genotyping test with sequential NGS when required may be a cost-effective and highly sensitive approach to CYP21A2 genotyping in our part of the world and in resource-poor settings.

3β-Hydroxysteroid Dehydrogenase Type 2 (3βHSD2) Deficiency due to a Novel Compound Heterozygosity of a Missense Mutation (p.Thr259Met) and Frameshift Deletion (p.Lys273ArgFs*7) in an Undervirilized Infant Male with Salt Wasting

Deficiency of 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2) is a rare type of congenital adrenal hyperplasia (CAH), causing impaired steroid hormone production in both adrenals and gonads. Phenotype ranges, according to the genetic defect, from the salt-wasting form in both sexes to undervirilization in males and virilization in females. We present a 13-month-old male infant who was admitted to the hospital with signs of adrenocortical insufficiency and genital ambiguity. Clinical presentation, hormonal profile, laboratory evaluation, and karyotype were suggestive of the salt-wasting form of CAH due to 3βHSD2 deficiency. Mutational analysis revealed a missense mutation c.776C>T (p.Thr259Met), inherited by the mother, and a frameshift deletion c.818-819delAA (p.Lys273ArgFs*7), inherited by the father. Both mutations are considered pathogenic. To our knowledge this is the first case of an undervirilized male infant with salt wasting bearing this pathogenic frameshift deletion p.Lys273ArgFs*7 in compound heterozygosity with the missense mutation p.Thr259Met.

Aldosterone signaling defect in young infants: single-center report and review

BACKGROUND

Aldosterone (Ald) is a crucial factor in maintaining electrolyte and water homeostasis. Defect in either its synthesis or function causes salt wasting (SW) manifestation. This disease group is rare, while most reported cases are sporadic. This study aimed to obtain an overview of the etiology and clinical picture of patients with the above condition and report our rare cases.

METHODS

A combination of retrospective review and case studies was conducted at the Pediatric Endocrine unit of The First Affiliated Hospital Sun Yat Sen University from September 1989 to June 2020.

RESULTS

A total of 187 patients with SW were enrolled, of which 90.4% (n = 169) were diagnosed with congenital adrenal hyperplasia (CAH). SW type 21-hydroxylase deficiency accounted for 98.8% (n = 167) of CAH diagnosis, while 1.2% (n = 2) was of lipoid CAH. Non-CAH comprised 9.6% (n = 18) of the total patients whose etiologies included SF-1 gene mutation (n = 1), X-linked adrenal hypoplasia congenita (n = 9), aldosterone synthase deficiency (ASD, n = 4), and pseudo-hypoaldosteronism type 1 (PHA1, n = 1). Etiologies were not identified in three patients. All of patients with ASD and PHA1 exhibited SW syndrome in their early neonatal period. DNA sequencing showed mutations of CYP11B2 for P1-P4 and NR3C2 for P5. P1 and P2 were sibling brothers affected by compound heterozygous mutations of c.1121G > A (p.R374Q) and c.1486delC p.(L496fs); likewise, P4 was identified with compound heterozygous mutations of c.1200 + 1G > A and c.240-1 G > T; meanwhile P3 demonstrated c.1303G > A p.(G435S) homozygous mutation in CYP11B2 gene. Lastly, P5 showed c.1768 C > T p.(R590*) heterozygous mutation in the NR3C2 gene.

CONCLUSION

Etiology of infant with aldosterone defect was mostly congenital. Renal and adrenal imaging are recommended to exclude renal causes. If clinical picture is suggestive, normal plasma Ald in early infancy cannot rule out aldosterone insufficiency.

Renin-aldosterone system evaluation over four decades in an extended family with autosomal dominant pseudohypoaldosteronism due to a deletion in the NR3C2 gene

Renal pseudohypoaldosteronism (PHA1) is a mild form of an aldosterone-resistance syndrome caused by mutations in the NR3C2 gene that codes for the mineralocorticoid receptor (MR). The disease is inherited as an autosomal dominant trait characterized by signs and symptoms of salt-losing in infancy. Disease manifestations could be severe in infancy but improve after the age of 1-3 years. Some affected members are asymptomatic and remain so life-long. In this study, we report the identification of a large deletion in the NR3C2 gene (c.1897+1_1898-1)_(c.*2955+?)del in renal PHA1 patients from an extended family spanning four generations. We prospectively evaluated the plasma renin activity and serum aldosterone profiles over four decades in symptomatic and asymptomatic affected family members. The benefits of early diagnosis on the clinical outcome were assessed as well. The long-term follow-up showed an age-dependent decrease in both plasma renin activity and serum aldosterone levels over the years. However, aldosterone levels remain high life-long. Thus, levels of aldosterone are a reliable marker to detect asymptomatic family members. The diagnosis of the proposita led to early diagnosis and therapy in other affected family members, significantly mitigating the clinical course. Despite the extremely elevated serum aldosterone levels during pregnancy, affected pregnant women did not experience any ill effects. However, this should be verified by observations in other adult patients.

Detection of a novel severe mutation affecting the CYP21A2 gene in a Chilean male with salt wasting congenital adrenal hyperplasia

PURPOSE

21-hydroxylase deficiency (21-OHD) is a congenital adrenal disease with more than 200 mutations published to date. The aim of this report is to describe a severe novel mutation of the CYP21A2 gene.

METHOD

We describe a case of a 39-year-old male diagnosed with a salt wasting congenital adrenal hyperplasia (SWCAH) due to 21-OHD. The genetic testing was done using a combination of three methods (PCR XL, SALSA-MLPA, and bidirectional sequencing) and finally an in silico analysis.

RESULTS

The genetic testing demonstrated three severe mutations of the CYP21A2 gene (p.Gln318*; c.290-13C>G; and p.Trp86*), being the last one a novel mutation not previously reported. The in silico modeling of the p.Trp86* (c.258G>A) showed a truncated CYP21A2 protein that loses all the main structural features required for activity, such as the HEM binding domain and the hormone binding site.

CONCLUSION

We present an adult man with an SWCAH due to 21-OHD who carried three severe mutations of the CYP21A2 gene, one of them, p.Trp86* (c.258G>A) has not been previously described.

Data on the 21-Hydroxylase deficient CAH patients and the identification of known/novel mutations in CYP21A2 gene

This article presents the dataset regarding spectrum of mutations in 21-Hydroxylase deficient CAH patients as described in “The spectrum of CYP21A2 mutations in Congenital Adrenal Hyperplasia in an Indian cohort” (R. Khajuria, R. Walia, A. Bhansali, R. Prasad, 2017) [1]. This dataset features about the CAH patients in the cohort, their classification into subtypes and finally screening the exon–intron boundaries of 21-Hydroxylase gene (CYP21A2) to detect common mutations, novel mutations along polymorphisms in the CYP21A2 gene. The specified large set of primers and the parameters for the mutation detection allow the identification and molecular characterization of CYP21A2 gene in the CAH patients.

Identifying Different Causes of Hyponatremia With Fractional Excretion of Uric Acid

BACKGROUND

There is controversy over the prevalence of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral or renal salt wasting (RSW), 2 syndromes with identical common clinical and laboratory parameters but different therapies. The traditional approach to the hyponatremic patient relies on volume assessment, but there are limitations to this method.

METHODS

We used an algorithm that relies on fractional excretion of urate (FEurate) to evaluate patients with hyponatremia and present 4 illustrative cases.

RESULTS

Overall, 2 patients had increased FEurate [normal: 4-11%], as is seen in SIADH and RSW. A diagnosis of SIADH was made in 1 patient by correcting the hyponatremia with 1.5% saline and observing a characteristic normalization of an elevated FEurate that is characteristic of SIADH as compared to FEurate being persistently increased in RSW. A patient with T-cell lymphoma had symmetrical leg edema due to lymphomatous obstruction of the inferior vena cava, postural hypotension, pleural effusion, ascites, decreased cardiac output and urine sodium level of 10mmol/L. Saline-induced excretion of dilute urines and undetectable plasma antidiuretic hormone were consistent with RSW. Furosemide, given for presumed heart failure, induced a profound diuresis that required large volumes of fluid resuscitation. A normal FEurate identified a reset osmostat in a transplant patient with a slowly developing pneumocystis carinii pneumonia. A volume-depleted hyponatremic patient with Addison׳s disease had a low FEurate of 1.4%.

CONCLUSIONS

These illustrative cases suggest that an approach to hyponatremia using FEurate may be a useful alternative to traditional volume-based approaches.