D-Bifunctional Protein Deficiency Diagnosis-A Challenge in Low Resource Settings: Case Report and Review of the Literature.

D-bifunctional protein deficiency (D-BPD) is a rare, autosomal recessive peroxisomal disorder that affects the breakdown of long-chain fatty acids. Patients with D-BPD typically present during the neonatal period with hypotonia, seizures, and facial dysmorphism, followed by severe developmental delay and early mortality. While some patients have survived past two years of age, the detectable enzyme activity in these rare cases was likely a contributing factor. We report a D-BPD case and comment on challenges faced in diagnosis based on a narrative literature review. An overview of Romania's first patient diagnosed with D-BPD is provided, including clinical presentation, imaging, biochemical, molecular data, and clinical course. Establishing a diagnosis can be challenging, as the clinical picture is often incomplete or similar to many other conditions. Our patient was diagnosed with type I D-BPD based on whole-exome sequencing (WES) results revealing a pathogenic frameshift variant of the HSD17B4 gene, c788del, p(Pro263GInfs*2), previously identified in another D-BPD patient. WES also identified a variant of the SUOX gene with unclear significance. We advocate for using molecular diagnosis in critically ill newborns and infants to improve care, reduce healthcare costs, and allow for familial counseling.

Diversity of Clinical and Molecular Characteristics in Korean Patients with 16p11.2 Microdeletion Syndrome.

16p11.2 copy number variations (CNVs) are increasingly recognized as one of the most frequent genomic disorders, and the 16p11.2 microdeletion exhibits broad phenotypic variability and a diverse clinical phenotype. We describe the neurodevelopmental course and discordant clinical phenotypes observed within and between individuals with identical 16p11.2 microdeletions. An analysis with the CytoScan Dx Assay was conducted on a GeneChip System 3000Dx, and the sample signals were then compared to a reference set using the Chromosome Analysis Suite software version 3.1. Ten patients from six separate families were identified with 16p11.2 microdeletions. Nine breakpoints (BPs) 4-5 and one BP2-5 of the 16p11.2 microdeletion were identified. All patients with 16p11.2 microdeletions exhibited developmental delay and/or intellectual disability. Sixty percent of patients presented with neonatal hypotonia, but muscle weakness improved with age. Benign infantile epilepsy manifested between the ages of 7-10 months (a median of 8 months) in six patients (60%). Vertebral dysplasia was observed in two patients (20%), and mild scoliosis was noted in three patients. Sixty percent of patients were overweight. We present six unrelated Korean families, among which identical 16p11.2 microdeletions resulted in diverse developmental trajectories and discordant phenotypes. The clinical variability and incomplete penetrance observed in individuals with 16p11.2 microdeletions remain unclear, posing challenges to accurate clinical interpretation and diagnosis.

Expanding the spectrum of congenital myopathies: prenatal onset with extreme hyperextension of the neck.

We describe the case of a male newborn presenting with a prenatal diagnosis of persistent hyperextension of the fetal neck and severe hypotonia and respiratory insufficiency at birth. Facial weakness, increased serum creatine kinase levels, and abnormal feeding, together with other signs, such as severe contractures, also classically associated with congenital myopathies prompted to perform a muscle biopsy showing internal rods suggestive of a possible nemaline myopathy. These findings suggest that a careful neurological examination should be performed in infants with persistent hyperextension of the fetal neck to exclude weakness and a possible underlying muscle disorder.

Hypotonia at Birth: A Case Study of ACTA-1 Mutation, a Congenital Myopathy.

Congenital myopathy is an uncommon neonatal disorder that can manifest in the neonatal period with severe features. Presentation with signs of global hypotonia and respiratory insufficiency are among the classic findings. Rapid diagnosis is essential for medical management and family support. This case study reviews the presentation of hypotonia in the newborn, followed by a path to a diagnosis of nemaline myopathy in the form of an ACTA-1 mutation. This review can aid the clinician in the diagnosis of patients in whom hypotonia is present at birth. Included is a discussion of the incidence, pathophysiology, diagnosis, and management of this devastating disease.

Similar metabolic pathways are affected in both Congenital Myasthenic Syndrome-22 and Prader-Willi Syndrome.

Loss of prolyl endopeptidase-like (PREPL) encoding a serine hydrolase with (thio)esterase activity leads to the recessive metabolic disorder Congenital Myasthenic Syndrome-22 (CMS22). It is characterized by severe neonatal hypotonia, feeding problems, growth retardation, and hyperphagia leading to rapid weight gain later in childhood. The phenotypic similarities with Prader-Willi syndrome (PWS) are striking, suggesting that similar pathways are affected. The aim of this study was to identify changes in the hypothalamic-pituitary axis in mouse models for both disorders and to examine mitochondrial function in skin fibroblasts of patients and knockout cell lines. We have demonstrated that Prepl is downregulated in the brains of neonatal PWS-IC-p/+m mice. In addition, the hypothalamic-pituitary axis is similarly affected in both Prepl-/- and PWS-IC-p/+m mice resulting in defective orexigenic signaling and growth retardation. Furthermore, we demonstrated that mitochondrial function is altered in PREPL knockout HEK293T cells and can be rescued with the supplementation of coenzyme Q10. Finally, PREPL-deficient and PWS patient skin fibroblasts display defective mitochondrial bioenergetics. The mitochondrial dysfunction in PWS fibroblasts can be rescued by overexpression of PREPL. In conclusion, we provide the first molecular parallels between CMS22 and PWS, raising the possibility that PREPL substrates might become therapeutic targets for treating both disorders.

Nemaline Myopathy in a Hypotonic Neonate: Diagnostic Approach for Early Detection and Management.

Neonatal hypotonia presents with low muscle tone and an array of symptoms that vary depending on the etiology. The differential diagnosis for this condition is complex. It is crucial to exclude life-threatening causes before following a diagnostic algorithm and performing additional tests. Given the wide range of clinical symptoms and etiologies for neonatal hypotonia, rapid genetic testing has the potential to expedite diagnosis, reduce invasive testing such as muscle biopsy, reduce hospital stays, and guide condition management.  A four-week-old girl was admitted to the emergency department (ED) with a one-day history of lethargy, poor feeding, congestion, cough, and hypoxemia. Given positive rhino-enterovirus testing and high inflammatory markers, antibiotics were administered. Imaging, venous blood gas, and blood cultures were negative, and the patient was admitted to the pediatric intensive care unit (PICU) for hypoxemia. After speech-language pathology (SLP) and occupational therapy (OT) evaluation, weak orofacial muscles and feeding issues resulted in a nasogastric tube placement. A swallow study revealed decreased pharyngeal contraction and post-swallow liquid residue. Laryngoscopy showed mild laryngomalacia and dysphagia with aspiration. Genetic testing identified an ACTA1 mutation and confirmed nemaline myopathy (NM). The patient's oxygen levels dropped further during sleep, resulting in diagnoses of severe obstructive and moderate-severe central sleep apnea. Treatment included oxygen therapy, SLP, physical therapy, albuterol, and cough assists. After discharge, the patient was frequently re-admitted with chronic respiratory failure and bronchiolitis and later had gastrostomy and tracheostomy tubes inserted.  This specific case highlights the importance of implementing a diagnostic algorithm for neonatal hypotonia. It is also important for physicians, especially emergency medicine (EM) providers, to first exclude infection, sepsis, and cardiac and respiratory organ failure before looking into other tests. Then, physicians should evaluate for more rare etiologies. In this patient's case, the hypotonia was due to a rare genetic disease, nemaline myopathy, and a multidisciplinary approach was used for this patient's care.

Progressive Dysphagia in Joubert Syndrome: A Report of a Rare Case.

Joubert syndrome is an uncommon, autosomal recessive disorder characterized by abnormal brain development involving the underdevelopment or absence of the cerebellar vermis. The classic clinical features include developmental delays, hypotonia, abnormal eye movements, and hyperpnea. On brain magnetic resonance imaging (MRI), an essential finding for the diagnosis of Joubert syndrome is a cerebellar and brainstem malformation called the molar tooth sign, characterized by a hypoplastic cerebellar vermis with dysplasia of the superior cerebellar peduncles. Here, we describe a case of a two-month-old female with an atypical presentation of Joubert syndrome. Her initial clinical presentation included respiratory distress and concerns for reflux complicated with aspiration pneumonia. Early recognition of clinical and radiologic findings for Joubert syndrome enables an early diagnosis, and therefore timely interventions for improving the child's development and quality of life.

5q31.3 Microdeletion syndrome: clinical and molecular characterization of two further cases.

The 5q31.3 microdeletion syndrome has recently emerged as a distinct clinical entity, and we report two new patients with de novo deletions of this region, bringing the total to seven. Similarly to previously reported cases, the phenotype of our patients is characterized by marked hypotonia, apnea, developmental delay, and feeding difficulties. Both patients had abnormal movements which did not correlate with epileptiform activity on electroencephalogram (EEG). Developmental brain changes on neuroimaging consisted of abnormalities predominantly affecting the white matter and frontal lobes. The 5q31.3 deleted regions overlap those of previously reported cases, and allow further refinement of the shortest region of overlap to 101 kb, including only three genes. Of these, the purine-rich element binding protein A (PURA) gene has an established role in brain development, and we propose that haploinsufficiency for this gene is primarily responsible for the neurodevelopmental features observed.

Further delineation of genotype-phenotype correlation in homozygous 2p21 deletion syndromes: first description of patients without cystinuria.

Homozygous contiguous gene deletion syndromes are rare. On 2p21, however, several overlapping homozygous gene deletion syndromes have been described, all presenting with cystinuria but otherwise distinct phenotypes. Hypotonia-cystinuria syndrome (HCS, OMIM606407) is characterized by infantile hypotonia, poor feeding, and growth hormone deficiency. Affected individuals carry homozygous deletions including the cystinuria gene SLC3A1 and the adjacent PREPL gene. Larger homozygous deletions in this region encompassing the PPM1B, SLC3A1, PREPL, and C2orf34 (CAMKMT) genes result in a more severe phenotype, the 2p21 deletion syndrome. A phenotype intermediate to HCS and the 2p21 deletion syndrome is termed atypical HCS and is caused by deletion of SLC3A1, PREPL, and C2orf34 (CAMKMT). Using high resolution SNP array molecular karyotyping we identified two siblings with a homozygous deletion of 83 kb partially encompassing the genes PREPL and C2orf34 (CAMKMT), but not the SLC3A1 gene. The affected siblings display a recognizable phenotype which is similar to atypical HCS with regard to growth failure and neuro-muscular features, but is characterized by lack of cystinuria. The patients also exhibit features which have not been reported to date such as cleft palate and genital abnormalities. In conclusion, we report the first patients with a homozygous 2p21 deletion syndrome without cystinuria and further delineate the complex genotype-phenotype correlations of homozygous microdeletion syndromes of this region.

An Unusual Case of Neonatal Hypotonia and Femur Fracture: Neuromuscular Variant of Glycogen Storage Disease Type IV.

Glycogen storage disease type IV (GSD IV) (OMIM #232500) is an autosomal recessive disorder caused by deficiency of the glycogen-branching enzyme. Here, we report a patient presenting with prematurity and severe hypotonia resulting from a complicated pregnancy with polyhydramnios. During her stay in the neonatal unit, the infant remained dependent on a ventilator, and her movements were mostly absent, except for occasional small movements of her fingers. A spontaneous fracture of femur shaft occurred in the postnatal fourth week. Whole-exome sequencing of DNA from the patient revealed a homozygous missense variant in the GBE1 gene (c.1693C>T, p.Arg565Trp). The variation detected in the index case was also confirmed by Sanger sequencing in the patient and respective parents. This study showed that the neuromuscular subtypes of GSD-IV should be considered as a possible differential diagnosis in severe neonatal hypotonia cases.

FKBP14 kyphoscoliotic Ehlers-Danlos syndrome misdiagnosed as Larsen syndrome: a case report.

Hereditary connective tissue disorders have overlapping phenotypes, particularly in regard to musculoskeletal features. This contributes to the challenge of phenotype-based clinical diagnoses. However, some hereditary connective tissue disorders have distinct cardiovascular manifestations that require early intervention and specific management. Molecular testing has increased the ability to categorize and diagnose distinct hereditary connective tissue disorders. A 42-yr-old female with a clinical diagnosis of Larsen syndrome from birth presented for genetic testing based on her recent diagnosis of premenopausal breast cancer. She had a past medical history of multiple carotid dissections. As she never had confirmatory molecular genetic testing for Larsen syndrome, whole-exome sequencing was utilized to assess both hereditary cancer predisposition syndromes and connective tissue disorders. A homozygous pathogenic variant in the FKBP14 gene was identified associated with FKBP14 kyphoscoliotic Ehlers-Danlos syndrome. We recommend that patients with a clinical diagnosis of Larsen syndrome undergo broad-based molecular sequencing for multiple hereditary connective tissue disorders. Molecular diagnosis is particularly crucial for all individuals who have a history of significant vascular events in the setting of a clinical diagnosis only. Early diagnosis of a hereditary connective tissue disorder with vascular features allows for screening and subsequent prevention of cardiovascular events.

Homozygous EXOSC3 c.395A>C Variants in Pontocerebellar Hypoplasia Type 1B: A Sibling Pair With Childhood Lethal Presentation and Literature Review.

Pontocerebellar hypoplasia type 1B (PCH1B) is an autosomal recessive neurodegenerative disorder that involves hypoplasia or atrophy of the cerebellum and pons. PCH1B is caused by mutations in EXOSC3, which encodes a subunit of the RNA exosome complex. The most frequently observed mutation in PCH1B patients is a c.395A>C (p.D132A) missense variant, for which the homozygous mutation typically results in milder symptoms compared to compound heterozygous mutations or homozygous mutations for other pathogenic variants. In the present study, we report on a sibling pair harboring homozygous EXOSC3 c.395A>C missense variants who deteriorated more rapidly than previously described. These cases expand the spectrum of clinical manifestations of PCH1B associated with this variant, highlighting the need for further research to determine predictive factors of PCH1B severity.

Hypotonic infant with PURA syndrome-related channelopathy successfully treated with pyridostigmine.

PURA syndrome is a rare, clinically heterogeneous disorder characterized by a wide spectrum of neurodevelopmental problems, and occasionally congenital heart defects, urogenital malformations, skeletal abnormalities and endocrine disorders. We describe the hospital course, diagnostic evaluations as well as neurologic and neuromuscular follow up of an infant diagnosed with PURA syndrome based on a pathogenic deletion at c.697_699 (p.Phe233del) of the PURA gene identified on whole exome sequencing. Upon initial examination, fluctuation of neuromuscular tone and reflexes were noted in conjunction with hypotonia and severe apneic episodes, suggestive of neuromuscular junction involvement. A definitive role of the neuromuscular junction has not been previously reported with PURA syndrome. The infant was started on pyridostigmine, an acetylcholinesterase inhibitor, with significant improvement in neuromuscular tone and motor movements. In addition, pyridostigmine also resulted in resolution of apneas and improved respiratory status which suggests its potential therapeutic role in patients with PURA syndrome.

A Rare Cause of Infantile-Onset Cardiomyopathy With Ocular Manifestations: Alström Syndrome.

We report a case of a five-month-old girl, who presented to our hospital with increased work of breathing, sweating since birth, and abnormal eye movements. On further evaluation, she was found to have restrictive cardiomyopathy, nystagmus, and hypotonia. Genetic workup showed a pathogenic variant in the ALSM1 gene, which confirmed the diagnosis of Alström syndrome. Alström syndrome is a rare condition that is characterized by a wide variety of multisystem manifestations, including visual disturbances, hearing impairment, and cardiomyopathy. This case report highlights Alström syndrome as one of the rare causes of early-onset infantile cardiomyopathy with nystagmus.

A Rare Case of Pontocerebellar Hypoplasia Type 1B With Literature Review.

A full-term female newborn was transferred to our neonatal intensive care unit (NICU) on day two of life for hypotonia. Physical examination was significant for overriding sutures, displaced small anterior fontanelle, axial hypotonia, extremity hypertonia, and slow deep tendon reflexes. She was also noted to have stridor with crying but had unlabored breathing without oxygen requirements and a normal heart examination. A brain magnetic resonance imaging (MRI) showed a large cisterna magna and cerebellar hypoplasia with the majority of the cerebellar vermis present, suggesting a possible Dandy-Walker variant (cerebellar vermis hypoplasia). Head computed tomography showed areas of close approximation of coronal sutures and no synostosis. During the NICU stay, our patient was evaluated by Pediatric Neurology who recommended a chromosomal microarray which returned normal. The patient also had some difficulty feeding initially, but she was able to feed efficiently and gain weight by the time of discharge. After discharge from NICU, her neurological status steadily declined, resulting in poor motor function and poor suck despite regular physical therapy, occupational therapy, and speech therapy. By three months of age, she developed failure to thrive and was admitted to the hospital for evaluation of the cause. Her neurological examination showed worsening of her axial hypotonia with very little movement in the upper extremities and hypertonia in the lower extremities. She had a weak suck with the inability to form a good seal on the nipple. A new heart murmur was noted and an echocardiogram showed a moderate-to-large atrial septal defect. A modified barium swallow study showed severe dysphagia for which she required gastrostomy tube placement for feeding. At follow-up with Neurology, she was noted to have progressive microcephaly, profound hypotonia, areflexia, and nystagmus. A second MRI showed worsening atrophy and increasing ventriculomegaly. By nine months of age, she developed respiratory failure, required a tracheostomy, and remained ventilator-dependent. Genetics was then consulted and recommended a brain malformation genetic panel. The patient was found to be heterozygous for two pathogenic variants in the EXOSC3 gene: c.155delC and D132A, which is consistent with a diagnosis of autosomal recessive pontocerebellar hypoplasia (PCH) type 1B. The mother was found to be a heterozygous carrier of the c.155delC pathogenic variant, while the father was a heterozygous carrier for the D132A variant, which confirms that the two variants are present on opposite alleles. PCH describes a rare group of 11 neurodegenerative disorders that are typically seen prenatally or shortly after birth. PCH1 is characterized as a combination of PCH and spinal muscular atrophy, with patients presenting with muscle weakness and global developmental delay. An increased understanding of PCH1 will lead to better care and counseling for patients and families.

PHIP variants associated with Chung-Jansen syndrome disrupt replication fork stability and genome integrity.

Chung-Jansen syndrome (CJS) is a rare, autosomal dominant disorder characterized by developmental delay, intellectual disability/cognitive impairment, behavioral challenges, obesity, and dysmorphic features. CJS is associated with heterozygous variants in PHIP (Pleckstrin-Homology Interacting Protein), a gene that encodes one of several substrate receptors for Cullin4-RING (CRL4) E3 ubiquitin ligase complex. Full length PHIP, also called DCAF14, was recently identified to function as a replication stress response protein. Herein, we report the identification of two PHIP missense variants identified by exome sequencing in unrelated individuals with CJS. The variants p.D488V and p.E963G occur in different functional elements of DCAF14- WD40 repeat domain and pleckstrin homology-binding region (PBR), respectively. Using DNA fiber assays, we reveal that cells expressing either variant exhibit defective replication fork progression in conditions of replication stress. Furthermore, unlike wild type DCAF14, both variants fail to accomplish DNA replication after exposure to genotoxic stress indicating a critical role of DCAF14 in protecting stalled replication forks. Thus, we have identified replication defects associated with CJS variants and predict replication-associated genome instability with CJS syndrome.

Acute Respiratory Distress in a Pediatric Patient With Prader-Willi and Moebius Syndromes.

Although acute respiratory infections or diseases such as asthma commonly cause respiratory distress in a pediatric patient, neuromuscular disorders must be considered as a possible etiology in patients with significant hypotonia, neurological deficits, and gross developmental delay. We present a case where a patient's lack of response to initial asthma exacerbation therapy led to a reconsideration of the original diagnosis and adaptation of the management plan. Our patient presented with a rare combination of two congenital disorders that cause hypotonia: Prader-Willi syndrome and Moebius syndrome. This case underlines the importance of considering atypical etiologies in pediatric patients with respiratory distress, while also illustrating the effectiveness of the atypical use of Dornase alfa in a patient with underlying neuromuscular disorders.

Biallelic SEPSECS variants in two siblings with pontocerebellar hypoplasia type 2D underscore the relevance of splice-disrupting synonymous variants in disease.

Noncoding and synonymous coding variants that exert their effects via alternative splicing are increasingly recognized as an important category of disease-causing variants. In this report, we describe two siblings who presented with hypotonia, profound developmental delays, and seizures. Brain magnetic resonance imaging (MRI) in the proband at 5 yr showed diffuse cerebral and cerebellar white matter volume loss. Both siblings later developed ventilator-dependent respiratory insufficiency and scoliosis and are currently nonverbal and nonambulatory. Extensive molecular testing including oligo array and clinical exome sequencing was nondiagnostic. Research genome sequencing under an institutional review board (IRB)-approved study protocol revealed that both affected children were compound-heterozygous for variants in the SEPSECS gene. One variant was an initiator codon change (c.1A > T) that disrupted protein translation, consistent with the observation that most disease-causing variants are loss-of-function changes. The other variant was a coding change (c.846G > A) that was predicted to be synonymous but had been demonstrated to disrupt mRNA splicing in a minigene assay. The SEPSECS gene encodes O-phosphoseryl-tRNA(Sec) selenium transferase, an enzyme that participates in the biosynthesis and transport of selenoproteins in the body. Variations in SEPSECS cause autosomal recessive pontocerebellar hypoplasia type 2D (PCHT 2D; OMIM #613811), a neurodegenerative condition characterized by progressive cerebrocerebellar atrophy, microcephaly, and epileptic encephalopathy. The identification of biallelic pathogenic variants in this family-one of which was a synonymous change not identified by prior clinical testing-not only ended the diagnostic odyssey for this family but also highlights the contribution of occult pathogenic variants that may not be recognized by standard genetic testing methodologies.

Inherited and de novo variants extend the etiology of TAOK1-associated neurodevelopmental disorder.

Alterations in the TAOK1 gene have recently emerged as the cause of developmental delay with or without intellectual impairment or behavioral abnormalities (MIM # 619575). The 32 cases currently described in the literature have predominantly de novo alterations in TAOK1 and a wide spectrum of neurodevelopmental abnormalities. Here, we report four patients with novel pathogenic TAOK1 variants identified by research genome sequencing, clinical exome sequencing, and international matchmaking. The overlapping clinical features of our patients are consistent with the emerging core phenotype of TAOK1-associated syndrome: facial dysmorphism, feeding difficulties, global developmental delay, joint laxity, and hypotonia. However, behavioral abnormalities and gastrointestinal issues are more common in our cohort than previously reported. Two patients have de novo TAOK1 variants (one missense, one splice site) consistent with most known alterations in this gene. However, we also report the first sibling pair who both inherited a TAOK1 frameshift variant from a mildly affected mother. Our findings suggest that incomplete penetrance and variable expressivity are relatively common in TAOK1-associated syndrome, which holds important implications for clinical genetic testing.