CAH-X Syndrome: Genetic and Clinical Profile

Congenital Adrenal Hyperplasia

We describe congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, which is the most common primary adrenal insufficiency in children and adolescents. In this comprehensive review of CAH, we describe presentations at different life stages depending on disease severity. CAH is characterized by androgen excess secondary to impaired steroidogenesis in the adrenal glands. Diagnosis of CAH is most common during infancy with elevated 17-hydroxyprogesterone levels on the newborn screen in the United States. However, CAH can also present in childhood, with late-onset symptoms such as premature adrenarche, growth acceleration, hirsutism, and irregular menses. The growing child with CAH is treated with hydrocortisone for glucocorticoid replacement, along with increased stress doses for acute illness, trauma, and procedures. Mineralocorticoid and salt replacement may also be necessary. Although 21-hydroxylase deficiency is the most common type of CAH, there are other rare types, such as 11β-hydroxylase and 3β-hydroxysteroid dehydrogenase deficiency. In addition, classic CAH is associated with long-term comorbidities, including cardiometabolic risk factors, impaired cognitive function, adrenal rest tumors, and bone health effects. Overall, early identification and treatment of CAH is important for the pediatric patient.

Genetic Characterization of a Cohort of Italian Patients with Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

INTRODUCTION

Defects in the steroid 21-hydroxylase gene (CYP21A2) cause 21-hydroxylase deficiency (21OHD), the main cause of congenital adrenal hyperplasia (CAH). The disease shows a broad spectrum of clinical forms, ranging from severe or classical (salt wasting, SW, and simple virilizing, SV), to mild late onset or nonclassical (NC). 21OHD affects 1 in 15,000 in its severe classic form and 1 in 200-1000 in its mild NC form. There are many studies reporting the frequency of CYP21A2 pathogenic variants in different populations; however, few of them provide comprehensive information about Italian patients. Here, we present genetic results from a cohort of 245 unrelated Italian individuals with clinical diagnosis of CAH due to 21OHD.

METHODS

A specific polymerase chain reaction (PCR) protocol combined with Sanger sequencing was used for CYP21A2 analysis. The multiplex ligation-dependent probe amplification (MLPA) assay was employed for copy number variation (CNV) determination.

RESULTS

One hundred fourteen (46.5%) of the index cases had the NC form, 57 (23.3%) had the SV form, and 74 (30.2%) presented the SW form of the disease. The most prevalent variant found in NC patients was the p.Val282Leu (51.3%), while the most frequent variants in the classical form were p.Ile173Asn (8.6%) and c.293-13C>G (26.0%). In our study, the frequency of large rearrangements was 15.3%, with CAH-X alleles representing 40% of all DEL/CONV. In addition, 12 alleles carried rare variants, and 1 had a novel variant p.(Arg342Gln). We observed phenotype-genotype correlation in 94.7% of cases. A complete concordance was observed in Groups 0 (enzyme activity completely impaired) where all patients had the SW form as expected. In Group A (0-1% residual enzyme activity), 78.4% of patients had the anticipated SW form while 21.6% were diagnosed with the SV form. Within Group B (~ 2% residual enzyme activity), 93.4% of patients exhibited SV form and 6.5% SW disease. Finally, 92.6% and 7.4% of patients belonging to Group C (enzyme partially impaired to ~ 20-60% residual activity) exhibited NC and SV phenotypes, respectively.

CONCLUSION

This work, representing a comprehensive genetic study, expanded the CYP21A2 variants spectrum of Italian patients with 21OHD and could be helpful in prenatal diagnosis and genetic counseling.

Long-Term Outcomes of Congenital Adrenal Hyperplasia

A plethora of negative long-term outcomes have been associated with congenital adrenal hyperplasia (CAH). The causes are multiple and involve supra-physiological gluco- and mineralocorticoid replacement, excess adrenal androgens both intrauterine and postnatal, elevated steroid precursor and adrenocorticotropic hormone levels, living with a congenital condition as well as the proximity of the cytochrome P450 family 21 subfamily A member 2 (CYP21A2) gene to other genes. This review aims to discuss the different long-term outcomes of CAH.