Expanding on the phenotypic spectrum of Woodhouse-Sakati syndrome due to founder pathogenic variant in DCAF17: Report of 58 additional patients from Qatar and literature review.

Woodhouse-Sakati syndrome (WSS) is a rare autosomal recessive neuroendocrine and ectodermal disorder caused by variants in the DCAF17 gene. In Qatar, the c.436delC variant has been reported as a possible founder pathogenic variant with striking phenotypic heterogeneity. In this retrospective study, we report on the clinical and molecular characteristics of additional 58 additional Qatari patients with WSS and compare them to international counterparts' findings. A total of 58 patients with WSS from 32 consanguineous families were identified. Ectodermal and endocrine (primary hypogonadism) manifestations were the most common presentations (100%), followed by diabetes mellitus (46%) and hypothyroidism (36%). Neurological manifestations were overlapping among patients with intellectual disability (ID) being the most common (75%), followed by sensorineural hearing loss (43%) and both ID and aggressive behavior (10%). Distinctive facial features were noted in all patients and extrapyramidal manifestations were uncommon (8.6%). This study is the largest to date on Qatari patients with WSS and highlights the high incidence and clinical heterogeneity of WSS in Qatar due to a founder variant c.436delC in the DCAF17 gene. Early suspicion of WSS among Qatari patients with hypogonadism and ID, even in the absence of other manifestations, would shorten the diagnostic odyssey, guide early and appropriate management, and avoid potential complications.

Gene therapy for spinal muscular atrophy: the Qatari experience.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by hypotonia, progressive muscle weakness, and wasting. Onasemnogene abeparvovec (Zolgensma®) is a novel gene therapy medicine, FDA-approved in May 2019 for the treatment of SMA. This study aimed to describe Qatari experience with onasemnogene abeparvovec by reviewing the clinical outcomes of 9 SMA children (7 SMA type 1 and 2 with SMA type 2) aged 4‒23 months treated between November 2019 and July 2020. Children <2 years with 5q SMA with a bi-allelic mutation in the SMN1 gene were eligible for gene therapy. Liver function (aspartate aminotransferase [AST], alanine aminotransferase [ALT], and total bilirubin), platelet count, coagulation profile, troponin-I levels, and motor scores (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders [CHOP INTEND]), were regularly monitored following gene therapy. All patients experienced elevated AST or ALT, two experienced high prothrombin time, and one experienced elevated bilirubin; all of these patients were asymptomatic. Furthermore, one event of vomiting after infusion was reported in one patient. Significant improvements in CHOP INTEND scores were observed following therapy. This study describes the short-term outcomes and safety of onasemnogene abeparvovec, which is well tolerated and shows promise for early efficacy.

A founder RAB27A variant causes Griscelli syndrome type 2 with phenotypic heterogeneity in Qatari families.

Griscelli syndrome type 2 (GS2) is a rare autosomal recessive disorder caused by pathogenic variants in the RAB27A gene and characterized by partial albinism, immunodeficiency, and occasional hematological and neurological involvement. We reviewed and analyzed the medical records of 12 individuals with GS2 from six families belonging to a highly consanguineous Qatari tribe and with a recurrent pathogenic variant in the RAB27A gene (NM_004580.4: c.244C > T, p.Arg82Cys). Detailed demographic, clinical, and molecular data were collected. Cutaneous manifestations were the most common presentation (42%), followed by neurological abnormalities (33%) and immunodeficiency (25%). The most severe manifestation was HLH (33%). Among the 12 patients, three patients (25%) underwent HSCT, and four (33%) died. The cause of death in all four patients was deemed HLH, providing evidence for this complication's fatal nature. Interestingly, two affected patients (16%) were asymptomatic. This report highlights the broad spectrum of clinical presentations of GS2 associated with a founder variant in the RAB27A gene (c.244C > T, p.Arg82Cys). Early suspicion of GS2 among Qatari patients with cutaneous manifestations, neurological findings, immunodeficiency, and HLH would shorten the diagnostic odyssey, guide early and appropriate treatment, and prevent fatal outcomes.

Clinical exome sequencing in 509 Middle Eastern families with suspected Mendelian diseases: The Qatari experience.

BACKGROUND: Clinical exome sequencing (CES) is rapidly becoming the diagnostic test of choice in patients with suspected Mendelian diseases especially those that are heterogeneous in etiology and clinical presentation. Reporting large CES series can inform guidelines on best practices for test utilization, and improves accuracy of variant interpretation through clinically-oriented data sharing. METHODS: This is a retrospective series of 509 probands from Qatar who underwent singleton or trio CES either as a reflex or naïve (first-tier) test from April 2014 to December 2016 for various clinical indications. RESULTS: The CES diagnostic yield for the overall cohort was 48.3% (n = 246). Dual molecular diagnoses were observed in 2.1% of cases; nearly all of whom (91%) were consanguineous. We report compelling variants in 11 genes with no established Mendelian phenotypes. Unlike reflex-WES, naïve WES was associated with a significantly shorter diagnostic time (3 months vs. 18 months, p < 0.0001). CONCLUSION: Middle Eastern patients tend to have a higher yield from CES than outbred populations, which has important implications in test choice especially early in the diagnostic process. The relatively high diagnostic rate is likely related to the predominance of recessive diagnoses (60%) since consanguinity and positive family history were strong predictors of a positive CES.

Natural history, with clinical, biochemical, and molecular characterization of classical homocystinuria in the Qatari population.

Classical homocystinuria (HCU) is the most common inborn error of metabolism in Qatar, with an incidence of 1:1800, and is caused by the Qatari founder p.R336C mutation in the CBS gene. This study describes the natural history and clinical manifestations of HCU in the Qatari population. A single center study was performed between 2016 and 2017 in 126 Qatari patients, from 82 families. Detailed clinical and biochemical data were collected, and Stanford-Binet intelligence, quality of life and adherence to treatment assessments were conducted prospectively. Patients were assigned to one of three groups, according to the mode of diagnosis: (a) late diagnosis group (LDG), (b) family screening group (FSG), and (c) newborn screening group (NSG). Of the 126 patients, 69 (55%) were in the LDG, 44 (35%) in the NSG, and 13 (10%) in the FSG. The leading factors for diagnosis in the LDG were ocular manifestations (49%), neurological manifestations (45%), thromboembolic events (4%), and hyperactivity and behavioral changes (1%). Both FSG and NSG groups were asymptomatic at time of diagnosis. NSG had significantly higher intelligence quotient, quality of life, and adherence values compared with the LDG. The LDG and FSG had significantly higher methionine levels than the NSG. The LDG also had significantly higher total homocysteine levels than the NSG and FSG. Regression analysis confirmed these results even when adjusting for age at diagnosis, current age, or adherence. These findings increase the understanding of the natural history of HCU and highlight the importance of early diagnosis and treatment. SYNOPSIS: A study in 126 Qatari patients with HCU, including biochemical, clinical, and other key assessments, reveals that patients with a late clinical diagnosis have a poorer outcome, hereby highlighting the importance of early diagnosis and treatment.

High diagnostic yield of clinical exome sequencing in Middle Eastern patients with Mendelian disorders.

Clinical exome sequencing (CES) has become an increasingly popular diagnostic tool in patients with heterogeneous genetic disorders, especially in those with neurocognitive phenotypes. Utility of CES in consanguineous populations has not yet been determined on a large scale. A clinical cohort of 149 probands from Qatar with suspected Mendelian, mainly neurocognitive phenotypes, underwent CES from July 2012 to June 2014. Intellectual disability and global developmental delay were the most common clinical presentations but our cohort displayed other phenotypes, such as epilepsy, dysmorphism, microcephaly and other structural brain anomalies and autism. A pathogenic or likely pathogenic mutation, including pathogenic CNVs, was identified in 89 probands for a diagnostic yield of 60%. Consanguinity and positive family history predicted a higher diagnostic yield. In 5% (7/149) of cases, CES implicated novel candidate disease genes (MANF, GJA9, GLG1, COL15A1, SLC35F5, MAGE4, NEUROG1). CES uncovered two coexisting genetic disorders in 4% (6/149) and actionable incidental findings in 2% (3/149) of cases. Average time to diagnosis was reduced from 27 to 5 months. CES, which already has the highest diagnostic yield among all available diagnostic tools in the setting of Mendelian disorders, appears to be particularly helpful diagnostically in the highly consanguineous Middle Eastern population.

Secondary NAD+ deficiency in the inherited defect of glutamine synthetase.

Glutamine synthetase (GS) deficiency is an ultra-rare inborn error of amino acid metabolism that has been described in only three patients so far. The disease is characterized by neonatal onset of severe encephalopathy, low levels of glutamine in blood and cerebrospinal fluid, chronic moderate hyperammonemia, and an overall poor prognosis in the absence of an effective treatment. Recently, enteral glutamine supplementation was shown to be a safe and effective therapy for this disease but there are no data available on the long-term effects of this intervention. The amino acid glutamine, severely lacking in this disorder, is central to many metabolic pathways in the human organism and is involved in the synthesis of nicotinamide adenine dinucleotide (NAD(+)) starting from tryptophan or niacin as nicotinate, but not nicotinamide. Using fibroblasts, leukocytes, and immortalized peripheral blood stem cells (PBSC) from a patient carrying a GLUL gene point mutation associated with impaired GS activity, we tested whether glutamine deficiency in this patient results in NAD(+) depletion and whether it can be rescued by supplementation with glutamine, nicotinamide or nicotinate. The present study shows that congenital GS deficiency is associated with NAD(+) depletion in fibroblasts, leukocytes and PBSC, which may contribute to the severe clinical phenotype of the disease. Furthermore, it shows that NAD(+) depletion can be rescued by nicotinamide supplementation in fibroblasts and leukocytes, which may open up potential therapeutic options for the treatment of this disorder.

Natural course of glutamine synthetase deficiency in a 3 year old patient.

Glutamine deficiency with hyperammonemia due to an inherited defect of glutamine synthetase (GS) was found in a 2 year old patient. He presented neonatal seizures and developed chronic encephalopathy. Thus, GS deficiency leads to severe neurological disease but is not always early lethal.

A Middle Eastern Founder Mutation Expands the Genotypic and Phenotypic Spectrum of Mitochondrial MICU1 Deficiency: A Report of 13 Patients.

MICU1 encodes a Ca2+ sensing, regulatory subunit of the mitochondrial uniporter, a selective calcium channel within the organelle's inner membrane. Ca2+ entry into mitochondria helps to buffer cytosolic Ca2+ transients and also activates ATP production within the organelle. Mutations in MICU1 have previously been reported in 17 children from nine families with muscle weakness, fatigue, normal lactate, and persistently elevated creatine kinase, as well as variable features that include progressive extrapyramidal signs, learning disabilities, nystagmus, and cataracts. In this study, we report the clinical features of an additional 13 patients from consanguineous Middle Eastern families with recessive mutations in MICU1. Of these patients, 12/13 are homozygous for a novel founder mutation c.553C>T (p.Q185*) that is predicted to lead to a complete loss of function of MICU1, while one patient is compound heterozygous for this mutation and an intragenic duplication of exons 9 and 10. The founder mutation occurs with a minor allele frequency of 1:60,000 in the ExAC database, but in ~1:500 individual in the Middle East. All 13 of these patients presented with developmental delay, learning disability, muscle weakness and easy fatigability, and failure to thrive, as well as additional variable features we tabulate. Consistent with previous cases, all of these patients had persistently elevated serum creatine kinase with normal lactate levels, but they also exhibited elevated transaminase enzymes. Our work helps to better define the clinical sequelae of MICU1 deficiency. Furthermore, our work suggests that targeted analysis of the MICU1 founder mutation in Middle Eastern patients may be warranted.

Newborn screening for remethylation disorders and vitamin B12 deficiency-evaluation of new strategies in cohorts from Qatar and Germany.

BACKGROUND: Newborn screening is a precondition for early diagnosis and successful treatment of remethylation disorders and classical homocystinuria (cystathionine-ß-synthase deficiency). Newborn screening for classical homocystinuria using total homocysteine measurement in dried blood spots has been very successfully performed for many years for newborns from Qatar. METHODS: A new optimized newborn screening strategy for remethylation disorders and homocystinuria was developed and evaluated for newborns from Qatar using total homocysteine measurement as first-tier and methionine, methionine-phenylalanine-ratio and propionylcarnitine as second-tiers. Proposed cut-offs were also retrospectively evaluated in newborn screening samples of 12 patients with remethylation disorders and vitamin B12 deficiency from Qatar and Germany. RESULTS: Over a 12 months period, the proposed strategy led to a decrease in the recall rate in homocysteine screening for Qatar from 1.09% to 0.68%, while allowing for additional systematic inclusion of remethylation disorders and vitamin B12 deficiency into the screening panel for Qatar. In the evaluated period the applied strategy would have detected all patients with classical homocystinuria identified by the previous strategy and in addition 5 children with maternal nutritional vitamin B12 deficiency and one patient with an isolated remethylation disorder. Additional retrospective evaluation of newborn screening samples of 12 patients from Germany and Qatar with remethlyation disorders or vitamin B12 deficiency showed that all of these patients would have been detected by the cut-offs used in the proposed new strategy. In addition, an adapted strategy for Germany using methionine, methionine-phenylalanine-ratio and propionylcarnitine as first-tier, and homocysteine as a second-tier test was also positively evaluated retrospectively. CONCLUSIONS: The proposed strategy for samples from Qatar allows inclusion of remethylation disorders and vitamin B12 deficiency in the screening panel, while lowering the recall rate. An adapted second-tier strategy is presented for screening in Germany and will be prospectively evaluated over the next years in a pilot project named "Newborn Screening 2020".

Newborn Screening for Vitamin B6 Non-responsive Classical Homocystinuria: Systematical Evaluation of a Two-Tier Strategy.

BACKGROUND: In classical homocystinuria (HCU, MIM# 236200) due to the deficiency of cystathionine ß-synthase (EC 4.2.1.22) there is a clear evidence for the success of early treatment. The aim of this study was to develop and evaluate a two-tier strategy for HCU newborn screening. METHODS: We reevaluated data from our newborn screening programme for Qatar in a total number of 125,047 neonates including 30 confirmed HCU patients. Our hitherto existing screening strategy includes homocysteine (Hcy) measurements in every child, resulting in a unique dataset for evaluation of two-tier strategies. Reevaluation included methionine (Met) levels, Met to phenylalanine (Phe) ratio, and Hcy. Four HCU cases identified after database closure were also included in the evaluation. In addition, dried blood spot samples selected by Met values >P97 in the newborn screening programs in Austria, Australia, the Netherlands, and Taiwan were analyzed for Hcy. RESULTS: Met to Phe ratio was found to be more effective for first sieve than Met, sorting out nearly 90% of normal samples. Only 10% of the samples would have to be processed by second-tier measurement of Hcy in dried blood spots. As no patient with HCU was found neither in the samples investigated for HCU, nor by clinical diagnosis in the other countries, the generalization of our two-tier strategy could only be tested indirectly. CONCLUSION: The finally derived two-tier algorithm using Met to Phe ratio as first- and Hcy as second-tier requires 10% first-tier positives to be transferred to Hcy measurement, resulting in 100% sensitivity and specificity in HCU newborn screening.

Aspartylglucosaminuria: unusual neonatal presentation in Qatari twins with a novel aspartylglucosaminidase gene mutation and 3 new cases in a Turkish family.

Aspartylglucosaminuria is a rare autosomal recessive lysosomal storage disorder leading early to a progressive intellectual disability. Monozygous Qatari twins presented with an unusual perinatal manifestation characterized by severe muscular hypotonia, scarce spontaneous movements, multiple contractures, and respiratory insufficiency. Biochemical investigations suggested aspartylglucosaminuria, and a novel homozygous mutation c.439T>C (p.S147P) was found in the aspartylglucosaminidase gene. However, it cannot be excluded that the unusual neonatal presentation is due to an additional autosomal recessive disease in this multiply consanguineous family. The classical aspartylglucosaminuria phenotype (progressive speech delay, psychomotor retardation, and behavioral abnormalities) was observed in 3 Turkish siblings. Although aspartylglucosaminuria was suspected early, the definite diagnosis was not confirmed until the age of 18 years. A novel homozygous mutation c.346C>T (p.R116W) was found. These 5 cases emphasize that aspartylglucosaminuria is panethnic and may possibly present with prenatal manifestation. Screening for aspartylglucosaminuria should be done in all patients with unexplained psychomotor retardation.

Glutamine supplementation in a child with inherited GS deficiency improves the clinical status and partially corrects the peripheral and central amino acid imbalance.

Glutamine synthetase (GS) is ubiquitously expressed in mammalian organisms and is a key enzyme in nitrogen metabolism. It is the only known enzyme capable of synthesising glutamine, an amino acid with many critical roles in the human organism. A defect in GLUL, encoding for GS, leads to congenital systemic glutamine deficiency and has been described in three patients with epileptic encephalopathy. There is no established treatment for this condition.Here, we describe a therapeutic trial consisting of enteral and parenteral glutamine supplementation in a four year old patient with GS deficiency. The patient received increasing doses of glutamine up to 1020 mg/kg/day. The effect of this glutamine supplementation was monitored clinically, biochemically, and by studies of the electroencephalogram (EEG) as well as by brain magnetic resonance imaging and spectroscopy.Treatment was well tolerated and clinical monitoring showed improved alertness. Concentrations of plasma glutamine normalized while levels in cerebrospinal fluid increased but remained below the lower reference range. The EEG showed clear improvement and spectroscopy revealed increasing concentrations of glutamine and glutamate in brain tissue. Concomitantly, there was no worsening of pre-existing chronic hyperammonemia.In conclusion, supplementation of glutamine is a safe therapeutic option for inherited GS deficiency since it corrects the peripheral biochemical phenotype and partially also improves the central biochemical phenotype. There was some clinical improvement but the patient had a long standing severe encephalopathy. Earlier supplementation with glutamine might have prevented some of the neuronal damage.