Beyond the adrenals: Organ manifestations in inherited primary adrenal insufficiency in children

Can Digenic, Tri-Allelic Inheritance of Variants in STAR and CYP11A1 Give Rise to Primary Adrenal Insufficiency? A Case Report

An eight-year old South Asian boy presenting with progressive hyperpigmentation was found to have primary adrenal insufficiency (PAI) in the form of isolated glucocorticoid deficiency. Follow up of this boy for nine years, until the age of 17 years showed normal pubertal onset and progression. Molecular evaluation, by targeted next generation sequencing of candidate genes linked to PAI revealed changes in two genes that are intricately linked in the early stages of steroid biosynthesis: compound heterozygous variants in STAR, c.465+1G>A and p.(E99K), plus a heterozygous rs6161 change in CYP11A1. No variants in other known causal genes were detected. The proband's mother was heterozygous for the c.465+1G>A STAR and rs6161 CYP11A1 variants, while the father was homozygous for the p.(E99K) alteration in STAR but wild-type for CYP11A1. Both parents had normal adrenal cortical function as revealed by short Synacthen tests. The STAR variant c.465+1G>A will lead to abnormal splicing of exon 4 in mRNA and the addition of the p.(E99K) variant, predicted damaging by SIFT and CADD, may be sufficient to cause PAI but this is by no means certain given that the unaffected father is homozygous for the latter change. The rs6161 CYP11A1 variant [c.940G>A, p.(E314K)] has recently been demonstrated to cause PAI in conjunction with a severe rare disruptive change on the other allele, however sequencing of the coding region of CYP11A1 revealed no further changes in this subject. We wondered whether the phenotype of isolated glucocorticoid deficiency had arisen in this child due to tri-allelic inheritance of a heterozygous CYP11A1 change along with the two STAR variants each of which contribute a partial loss-of-function burden that, when combined, is sufficient to cause PAI or if the loss-of-function c.465+1G>A combined with the presumed partial loss-of-function p.(E99K) in STAR could be causative.

A rare and preventable aetiology of neurodevelopmental delay and epilepsy: familial glucocorticoid deficiency

OBJECTIVES

Familial glucocorticoid deficiency (FGD) is a rare autosomal recessive disorder characterised by isolated glucocorticoid deficiency. Melanocortin receptor 2 (MC2R) mediates the functions of adrenocorticotropic hormone (ACTH) in the adrenal cortex. MC2R accessory protein (MRAP) is a transmembrane protein involved in the trafficking of MC2R to the cell surface. Mutations in MC2R and MRAP genes cause FGD type 1 and 2. In the present case series, we evaluate the clinical characteristics and long-term follow-up of six cases with FGD due to mutations in MC2R and MRAP.

CASE PRESENTATION

Data of six cases with FGD (five with mutations in MC2R and one with a mutation in MRAP) who were being followed at our paediatric endocrine centre was evaluated. Diagnosis of FGD was considered in case of elevated ACTH and inappropriately low cortisol level, and exclusion of other aetiologies. The main presenting complaints were hyperpigmentation and hypoglycaemic convulsion in all cases. During a follow-up period of 26-115 months, one patient with homozygous 560delT mutation in MC2R, one female with G226R mutation in MC2R and one female with IVS3ds+1delG mutation in MRAP had a neurodevelopmental delay (NDD), while the other three patients had normal neurodevelopment.

CONCLUSIONS

FGD patients due to MC2R and MRAP mutations with early diagnosis and compliance to the hydrocortisone therapy had normal neurodevelopment, while delay in diagnosis and poor compliance was associated with severe hypoglycaemic convulsions and subsequent complications NDD.