Xp21 deletion in female patients with intellectual disability: Two new cases and a review of the literature

Clinical and Molecular Genetic Analyses of a Girl With Isolated Nephrogenic Diabetes Insipidus due to Contiguous Gene Deletion Involving AVPR2 and L1CAM

Loss-of-function mutations of AVPR2 and L1CAM result in nephrogenic diabetes insipidus (NDI) and L1 syndrome. These diseases are inherited in an X-linked recessive manner. Females with heterozygous variants can be affected owing to skewed X-chromosome inactivation (XCI). A 3-year-old girl with normal development was presented with polydipsia and polyuria, and diagnosed of NDI through an improper response to water restriction and desmopressin administration. A targeted genome capture sequencing for X chromosome confirmed Xq28 microdeletion involving AVPR2 and L1CAM, derived from mother with mosaicism of the deletion. No pathogenic variants were identified in the paternal X allele nor in AQP2, another causative gene of NDI. XCI was exclusively skewed toward the maternal X chromosome in hair, oral mucosa, and blood, while it was random in nails and renal tubular epithelial cells (RTECs). Both AVPR2 and L1CAM mRNA expression in the patient's RTECs were significantly reduced compared to those of controls, with AVPR2 showing a more pronounced decrease. Thus, we demonstrated for the first time that NDI can develop in a female with a AVPR2 deletion despite of random XCI. Moreover, the absence of L1 syndrome in the female patient was caused most probably through organ-dependent skewed XCI in the deletion allele.

Genetic and Clinical Characterization of Complex Glycerol Kinase Deficiency in Two Male Siblings: A Case Report

Complex glycerol kinase deficiency (CGKD), also known as Xp21 contiguous gene deletion syndrome, is a rare X-linked recessive disorder resulting from partial deletion of the Xp21.3 chromosomal region. CGKD encompasses several loci, including glycerol kinase (GK), Duchenne muscular dystrophy (DMD), X-linked adrenal hypoplasia congenita (NR0B1), and intellectual developmental disorder (IL1RAPL1). We present the cases of two male siblings diagnosed with CGKD. The elder sibling was initially suspected of having congenital adrenal hypoplasia (CAH). Whole exome sequencing (WES) revealed an interstitial deletion of 6.6 Mb on Xp21.3p21.1, encompassing critical genes including GK, DMD, NR0B1, and IL1RAPL1. The younger sibling was diagnosed shortly after birth based on family history, clinical and biochemical findings. The presented report highlights the diagnostic challenges associated with CGKD and the important role of genetic testing in confirming the diagnosis. A multidisciplinary team approach is necessary.

[Xp21 contiguous gene deletion syndrome]

Contiguous gene syndromes (CGS) arise from microdeletions and other aberrations of a chromosome region containing several gene loci. One of the CGSs is Xp21 contiguous gene deletion syndrome (Xp21.3-p21.2) (Xp21 deletion syndrome). Slightly more than 100 male patients suffering from Xp21 contiguous gene deletion have been described in the world literature. This article describes a clinical case of a boy with Xp21 deletion syndrome. Chromosomal microarray analysis revealed a microdeletion of the X chromosome region from position 28085320 to position 33391678 with a size of 5306358 bp, including 11 genes in the imbalance region. The illness declared itself in the neonatal period and manifested early and rapidly as primary adrenal insufficiency (PAI) on the first and second days after birth, with severe metabolic disorders. At 2 years and 7 months, an increase in transaminases was detected for the first time due to metabolic disorders caused by PAI, which led to a misdiagnosis of autoimmune hepatitis. At 2 years and 10 months, the signs of myopathic syndrome were noted, and primary muscular dystrophy was diagnosed. The patient had a pronounced psychomotor development delay from an early age. The child's mother was diagnosed with the same mutation, including 11 genes in the imbalance region. The hereditary history showed the death of the first boy in the family due to PAI at the age of 6 weeks, which should have been the reason for a comprehensive assessment of the clinical situation and timely medical and genetic counseling to prevent the birth of a sick child from subsequent pregnancies.

Pseudo-hypertriglyceridemia in a 2-year-old male with global developmental delay, myopathy and adrenal hypoplasia

Pseudo-hypertriglyceridemia is an overestimation of serum triglyceride levels due to laboratory assays that measure free glycerol concentrations instead of triglycerides directly. Consequently, conditions presenting with elevated levels of endogenous or exogenous free glycerol, such as glycerol kinase deficiency, result in an overestimation of serum triglycerides. Glycerol kinase deficiency (GKD) is caused by pathogenic variants of the GK gene on chromosome Xp21. GKD is characterized biochemically by hyperglycerolaemia and glyceroluria. We herein report a 2-year-old male presented with a history of global developmental delay, axial hypotonia, poor head control and inability to sit unassisted or walk with elevated triglycerides at 683 (normal 44-157 mg/dL). Organic acid analysis showed abnormal accumulation of glycerol. Chromosomal microarray results showed a 4.2 Mb deletion of Xp21.3p21.1 (29296579-33551038) including complete copies of GK, DMD, and NR0B1 genes as well as multiple exons of IL1RAPL1. This confirmed his glycerol kinase deficiency (GKD) as part of the Xp21 continuous gene deletion syndrome. Elevated triglycerides were then recognized as pseudo-hypertriglyceridemia after the diagnosis. The younger sister and the mother have presented with developmental delay, and have been found to have same mutation. This family highlights the importance recognizing pseudohypertriglyceridemia and diagnostic challenges. Earlier identification through urine organic acid analysis could have been made. The combination of clinical presentations and increased glycerol should cause suspicion for GKD.

Delayed diagnosis of complex glycerol kinase deficiency in a Chinese male infant: a case report

BACKGROUND

Xp21 contiguous gene deletion syndrome is a rare genetic metabolic disorder with poor prognosis in infants, involving deletions of one or more genes in Xp21. When deletions of adrenal hypoplasia (AHC), Duchenne muscular dystrophy (DMD), and chronic granulomatosis (CGD) loci are included, complex glycerol kinase deficiency (CGKD) can be diagnosed. We present a case of CGKD that was initially misdiagnosed and died during treatment in our hospital in terms of improving our understanding of the clinical features and diagnosis of this disease, as well as highlighting the need for more precise dosing of corticosteroid replacement therapy.

CASE PRESENTATION

A 48-day-old full-term male infant was transferred to our medical center with global growth delay and persistent vomiting. Routine laboratory tests revealed hyperkalemia, hyponatremia, and a high level of creatine kinase. The initial diagnosis was adrenal cortical hyperplasia (ACH), then revised to adrenocortical insufficiency with a normal level of ACTH detected. After supplementing the routine lipid test and urinary glycerol test, CGKD was diagnosed clinically due to positive triglyceridemia and urinary glycerol, and the follow-up gene screening further confirmed the diagnosis. The boy kept thriving after corticosteroid replacement and salt supplementation. While levels of serum ACTH and cortisol decreased and remained low after corticosteroid replacement was administered. The patient died of acute type 2 respiratory failure and hypoglycemia after an acute upper respiratory tract infection, which may be the result of adrenal crisis after infection. Infants with CGKD have a poor prognosis, so physicians should administer regular follow-ups, and parents counseling during treatment to improve the survival of patients.

CONCLUSIONS

Overall, CGKD, although rare, cannot be easily excluded in children with persistent vomiting. Extensive blood tests can help to detect abnormal indicators. Adrenal crisis needs to be avoided as much as possible during corticosteroid replacement therapy.

A Multi-Disciplinary Team Approach to Genomic Testing for Drug-Resistant Epilepsy Patients—The GENIE Study

Background. The genomic era has led to enormous progress in clinical care and a multi-disciplinary team (MDT) approach is imperative for integration of genomics into epilepsy patient care. Methods. The MDT approach involved patient selection, genomic testing choice, variant discussions and return of results. Genomics analysis included cytogenomic testing and whole exome sequencing (WES). Neurologist surveys were undertaken at baseline and after genomic testing to determine if genomic diagnoses would alter their management, and if there was a change in confidence in genomic testing and neurologist perceptions of the MDT approach. Results. The total diagnostic yield from all genomic testing was 17% (11/66), with four diagnoses from cytogenomic analyses. All chromosomal microarray (CMA) diagnoses were in patients seen by adult neurologists. Diagnostic yield for WES was 11% (7/62). The most common gene with pathogenic variants was DCX, reported in three patients, of which two were mosaic. The genomic diagnosis impacted management in 82% (9/11). There was increased confidence with integrating genomics into clinical care (Pearson chi square = 83, p = 0.004) and qualitative comments were highly supportive of the MDT approach. Conclusions. We demonstrated diagnostic yield from genomic testing, and the impact on management in a cohort with drug-resistant epilepsy. The MDT approach increased confidence in genomic testing and neurologists valued the input from this approach. The utility of CMA was demonstrated in epilepsy patients seen by adult neurologists as was the importance of considering mosaicism for previously undiagnosed patients.

Molecular cytogenetic characterization of 16p11.2 microdeletions with diverse prenatal phenotypes: Four cases report and literature review

OBJECTIVE

Chromosome 16p11.2 deletions have been recognized as a genetic disorder with well-described postnatal phenotypes. However, the prenatal manifestations are atypical for lacking of enough evidence.

CASE REPORT

Four pregnant women underwent amniocentesis for cytogenetic analysis and chromosomal microarray analysis (CMA) because of various indications for prenatal diagnosis: prenatal ultrasound abnormalities (cases 1, 2 and 4) and the childbearing history of cerebral palsy child (case 3). No overlapping phenotypes were observed in cases 1, 2 and 4, which might indicate phenotypic diversities in prenatal phenotypes for 16p11.2 microdeletion. All four fetuses showed normal karyotypic results while CMA identified 0.303-0.916 Mb microdeletions of 16p11.2, encompassing BP2-BP3 and BP4-BP5 regions separately. According to the parental CMA verification, case 1 carried a maternal inherited duplication in the region of Xp22.33 and a de novo deletion in the region of Xp21.1. All parents opted for the termination of pregnancies based upon genetic counselling.

CONCLUSION

Our findings enriched the intrauterine phenotypic features of 16p11.2 microdeletions, which would be beneficial for genetic counselling in clinic. In addition, preimplantation genetic testing was recognized as a first-tier approach for such carriers if they intended to conceive again.

Impact of estrogen deficiency on diaphragm and leg muscle contractile function in female mdx mice

Female carriers of Duchenne muscular dystrophy (DMD) presenting with DMD symptomology similar to males with DMD, such as skeletal muscle weakness and cardiomyopathy, are termed manifesting carriers. There is phenotypic variability among manifesting carriers including the age of onset, which can range from the first to fourth decade of life. In females, estrogen levels typically begin to decline during the fourth decade of life and estrogen deficiency contributes to loss of muscle strength and recovery of strength following injury. Thus, we questioned whether the decline of estrogen impacts the development of DMD symptoms in females. To address this question, we studied 6-8 month-old homozygous mdx female mice randomly assigned to a sham or ovariectomy (OVX) surgical group. In vivo whole-body plethysmography assessed ventilatory function and diaphragm muscle strength was measured in vitro before and after fatigue. Anterior crural muscles were analyzed in vivo for contractile function, fatigue, and in response to eccentric contraction (ECC)-induced injury. For the latter, 50 maximal ECCs were performed by the anterior crural muscles to induce injury. Body mass, uterine mass, hypoxia-hypercapnia ventilatory response, and fatigue index were analyzed by a pooled unpaired t-test. A two-way ANOVA was used to analyze ventilatory measurements. Fatigue and ECC-injury recovery experiments were analyzed by a two-way repeated-measures ANOVA. Results show no differences between sham and OVX mdx mice in ventilatory function, strength, or recovery of strength after fatigue in the diaphragm muscle or anterior crural muscles (p ≥ 0.078). However, OVX mice had significantly greater eccentric torque loss and blunted recovery of strength after ECC-induced injury compared to sham mice (p ≤ 0.019). Although the results show that loss of estrogen has minimal impact on skeletal muscle contractile function in female mdx mice, a key finding suggests that estrogen is important in muscle recovery in female mdx mice after injury.

A novel Xp11.22-22.33 deletion suggesting a possible mechanism of congenital cervical spinal muscular atrophy

BACKGROUND

Congenital cervical spinal muscular atrophy (CCSMA) is a rare, nonprogressive, neurogenic disorder characterized by symmetric arthrogryposis and motor deficits mainly confined to upper extremities. Since its first proposal by Darwish et al. 39 years ago, only few cases have ever been reported. Vascular insult to the anterior horn of cervical spinal cord during fetal development was speculated to be the cause, however, the exact pathogenesis is still not well understood.

METHODS

In this study, whole-exome sequencing (WES) and copy number variation (CNV) analysis were conducted on a definitive CCSMA patient, confirmed by the clinical manifestations and other supplementary examinations.

RESULTS

On physical examination, the patient was mainly characterized by symmetric, congenital, nonprogressive contractures, hypotonia, and muscle weakness mainly confined to the upper limbs, which were further supported by MRI and electromyography. Neuromuscular biopsy of the deltoid muscle demonstrated the type 1 myofiber predominance without any infiltration of inflammatory cells. The WES and CNV analysis unveiled a de novo Xp11.22-22.33 deletion. On further examination of the genes contained within this segment, we recognize UBA1 gene as the most likely pathogenic gene. Ubiquitin-like modifier activating enzyme 1 is encoded by UBA1 gene (MIM 314370) located in Xp11.3 and is a critical protein that plays a vital role in ubiquitin-proteasome system and autophagy. It is well documented that UBA1 gene mutation causes X-linked infantile spinal muscular atrophy (XL-SMA), which manifests phenotypes of arthrogryposis, hypotonia, and myopathic face. Type 2 XL-SMA, which follows a nonprogressive and nonlethal course is very similar to the presentations of CCSMA.

CONCLUSION

The phenotypic similarities between this CCSMA case and XL-SMA prompt us to hypothesize a possible connection between UBA1 gene deficit and the pathogenesis of CCSMA. Our study is the first to demonstrate that CCSMA might have a genetic etiology, thus, expanding our insights into the underlying cause of CCSMA.

An overview of inborn errors of metabolism manifesting with primary adrenal insufficiency

Primary adrenal insufficiency (PAI) results from an inability to produce adequate amounts of steroid hormones from the adrenal cortex. The most common causes of PAI are autoimmune adrenalitis (Addison's disease), infectious diseases, adrenalectomy, neoplasia, medications, and various rare genetic syndromes and inborn errors of metabolism that typically present in childhood although late-onset presentations are becoming increasingly recognized. The prevalence of PAI in Western countries is approximately 140 cases per million, with an incidence of 4 per 1,000,000 per year. Several pitfalls in the genetic diagnosis of patients with PAI exist. In this review, we provide an in-depth discussion and overview on the inborn errors of metabolism manifesting with PAI, including genetic diagnosis, genotype-phenotype relationships and counseling of patients and their families with a focus on various enzymatic deficiencies of steroidogenesis.

Phenotypic Variability of Dystrophinopathy Symptomatic Female Carriers

BACKGROUND

Dystrophinopathies are X-linked muscular dystrophies characterized by pathogenic mutations in the dystrophin gene. Symptomatic dystrophinopathy female carriers may present with limb-girdle weakness. The diagnosis may be challenging in the absence of affected male relatives. We aimed to describe the phenotypic variability in a series of molecular-confirmed female dystrophinopathy patients.

METHODS

This is a retrospective analysis of medical records from 1997 to 2015.

RESULTS

Ten female dystrophinopathy patients were selected, two with unusual phenotypes: one with early joint contractures muscular dystrophy and the other with very late onset myopathy. Muscle imaging studies demonstrated predominant asymmetric fat replacement. Muscle biopsy immunohistochemistry demonstrated clear mosaic pattern in two cases and only subtle reduction of dystrophin intensity in three.

CONCLUSIONS

Adequate diagnosis is fundamental for genetic counseling and cardiologic follow-up. Female patients with dystrophinopathy may present unusual phenotypes such as early contractures and very late onset myopathy.