Single-center experience of congenital disorders of glycosylation syndrome screening in Tunisia: A retrospective study over a 15-year period (2007-2021).

BACKGROUND: We report the results gathered over 15 years of screening for congenital disorders of glycosylation syndrome (CDGS) in Tunisia according to clinical and biochemical characteristics. METHODS: Our laboratory received 1055 analysis requests from various departments and hospitals, for children with a clinical suspicion of CDGS. The screening was carried out through separation of transferrin isoforms by capillary zone electrophoresis. RESULTS: During the 15-year period, 23 patients were diagnosed with CDGS (19 patients with CDG-Ia, three patients with CDG-IIx, and one patient with CDG-X). These patients included 13 boys and 10 girls aged between 3 months and 13 years, comprising 2.18 % of the total 1055 patients screened. The incidence for CDGS was estimated to be 1:23,720 live births (4.21 per 100,000) in Tunisia. The main clinical symptoms related to clinical disease state in newborn and younger patients were psychomotor retardation (91 %), cerebellar atrophy (91 %), ataxia (61 %), strabismus (48 %), dysmorphic symptoms (52 %), retinitis pigmentosa, cataract (35 %), hypotonia (30 %), and other symptoms. CONCLUSION: In Tunisia, CDGS still remains underdiagnosed or misdiagnosed. The resemblance to other diseases, especially neurological disorders, and physicians' unawareness of the existence of these diseases are the main reasons for the underdiagnosis. In routine diagnostics, the screening for CDGS by biochemical tests is mandatory to complete the clinical diagnosis.

Identification of mutations that causes glucose-6-phosphate transporter defect in tunisian patients with glycogenosis type 1b.

BACKGROUND: Glycogen storage disease type 1b (GSD1b) is an autosomal recessive lysosomal storage disease caused by defective glucose-6-phosphate transporter encoded by SLC37A4 leading to the accumulation of glycogen in various tissues. The high rate of consanguineous marriages in Tunisian population provides an ideal environment to facilitate the identification of homozygous pathogenic mutations. We aimed to determine the clinical and genetic profiles of patients with GSD1b to evaluate SLC37A4 mutations spectrum in Tunisian patients. METHODS: All exons and flanking intron regions of SLC37A4 gene were screened by direct sequencing to identify mutations and polymorphisms in three unrelated families with GSD1b. Bioinformatics tools were then used to predict the impacts of identified mutations on the structure and function of protein in order to propose a function-structure relationship of the G6PT1 protein. RESULTS: Three patients (MT, MB and SI) in Families I, II and III who had the severe phenotype were homoallelic for the two identified mutations: p.R300H (famillies I, II) and p.W393X (Family III), respectively. One of the alterations was a missense mutation p.R300H of exon 6 in SLC37A4 gene. The analysis of the protein structure flexibility upon p.R300H mutation using DynaMut tool and CABS-flex 2.0 server showed that the reported mutation increase the molecule flexibility of in the cytosol region and would probably lead to significant conformational changes. CONCLUSION: This is the first Tunisian report of SLC37A4 mutations identified in Tunisia causing the glycogenosis type Ib disease. Bioinformatics analysis allowed us to establish an approximate structure-function relationship for the G6PT1 protein, thereby providing better genotype/phenotype correlation knowledge.

Molecular characterization of CTNS mutations in Tunisian patients with ocular cystinosis.

BACKGROUND: Ocular cystinosis is a rare autosomal recessive disorder characterized by intralysosomal cystine accumulation in renal, ophthalmic (cornea, conjunctiva), and other organ abnormalities. Patients with ocular cystinosis are mostly asymptomatic and typically experience mild photophobia due to cystine crystals in the cornea observed accidently during a routine ocular examination. The ocular cystinosis is associated with different mutations in CTNS gene. Cysteamine therapy mostly corrects the organ abnormalities. METHODS: This study was performed in collaboration with the department of ophthalmology of Farhat Hached Hospital. The Optical Coherence Tomography (OCT) of the cornea and retinal photography were used to search cystine crystals within the corneas and conjunctiva in eight Tunisian patients. Screening for the common 57-kb deletion was performed by standard multiplex PCR, followed by direct sequencing of the entire CTNS gene. RESULTS: The studied patients were found to have cystine crystal limited anterior corneal stroma and the conjunctiva associated with retinal crystals accumulation. CTNS gene sequencing disclosed 7 mutations: three missense mutations (G308R, p.Q88K, and p.S139Y); one duplication (C.829dup), one framshift mutation (p.G258f), one splice site mutation (c.681 + 7delC) and a large deletion (20,327-bp deletion). Crystallographic structure analysis suggests that the novel mutation p.S139Y is buried in a first transmembrane helix closed to the lipid bilayer polar region, introducing a difference in hydrophobicity which could affect the hydrophobic interactions with the membrane lipids. The second novel mutation p.Q88K which is located in the lysosomal lumen close to the lipid membrane polar head region, introduced a basic amino acid in a region which tolerate only uncharged residue. The third missense mutation introduces a positive change in nonpolar tail region of the phospholipid bilayer membrane affecting the folding and stability of the protein in the lipid bilayer. CONCLUSIONS: Our data demonstrate that impaired transport of cystine out of lysosomes is the most common, which is obviously associated with the mutations of transmembrane domains of cystinosine resulting from a total loss of its activity.

Alpha-mannosidosis in Tunisian consanguineous families: Potential involvement of variants in GHR and SLC19A3 genes in the variable expressivity of cognitive impairment.

Alpha-Mannosidosis (AM) is an ultra-rare storage disorder caused by a deficiency of lysosomal alpha-mannosidase encoded by the MAN2B1 gene. Clinical presentation of AM includes mental retardation, recurrent infections, hearing loss, dysmorphic features, and motor dysfunctions. AM has never been reported in Tunisia. We report here the clinical and genetic study of six patients from two Tunisian families with AM. The AM diagnosis was confirmed by an enzymatic activity assay. Genetic investigation was conducted by Sanger sequencing of the mutational hotspots for the first family and by ES analysis for the second one. In the first family, a frameshift duplication p.(Ser802GlnfsTer129) was identified in the MAN2B1 gene. For the second family, ES analysis led to the identification of a missense mutation p.(Arg229Trp) in the MAN2B1 gene in four affected family members. The p.(Ser802GlnfsTer129) mutation induces a premature termination codon which may trigger RNA degradation by the NMD system. The decrease in the levels of MAN2B1 synthesis could explain the severe phenotype observed in the index case. According to the literature, the p.(Arg229Trp) missense variant does not have an impact on MAN2B1 maturation and transportation, which correlates with a moderate clinical sub-type. To explain the intra-familial variability of cognitive impairment, exome analysis allowed the identification of two likely pathogenic variants in GHR and SLC19A3 genes potentially associated to cognitive decline. The present study raises awareness about underdiagnosis of AM in the region that deprives patients from accessing adequate care. Indeed, early diagnosis is critical in order to prevent disease progression and to propose enzyme replacement therapy.

Fucosidosis in Tunisian patients: mutational analysis and homology-based modeling of FUCA1 enzyme.

BACKGROUND: Fucosidosis is an autosomal recessive lysosomal storage disease caused by defective alpha-L-fucosidase (FUCA1) activity, leading to the accumulation of fucose-containing glycolipids and glycoproteins in various tissues. Clinical features include angiokeratoma, progressive psychomotor retardation, neurologic signs, coarse facial features, and dysostosis multiplex. METHODS: All exons and flanking intron regions of FUCA1 were screened by direct sequencing to identify mutations and polymorphisms in three unrelated families with fucosidosis. Bioinformatics tools were then used to predict the impacts of novel alterations on the structure and function of proteins. Furthermore, the identified mutations were localized onto a 3D structure model using the DeepView Swiss-PdbViewer 4.1 software, which established a function-structure relationship of the FUCA1 proteins. RESULTS: Four novel mutations were identified in this study. Two patients (P1 and P2) in Families 1 and 2 who had the severe phenotype were homoallelic for the two identified frameshift mutations p.K57Sfs*75 and p.F77Sfs*55, respectively. The affected patient (P3) from Family 3, who had the milder phenotype, was heterozygous for the novel missense mutation p.G332E and the novel splice site mutation c.662+5g>c. We verified that this sequence variation did not correspond to a polymorphism by testing 50 unrelated individuals. Additionally, 16 FUCA1 polymorphisms were identified. The structure prediction analysis showed that the missense mutation p.G332E would probably lead to a significant conformational change, thereby preventing the expression of the FUCA1 protein indeed; the 3D structural model of the FUCA1 protein reveals that the glycine at position 332 is located near a catalytic nucleophilic residue. This makes it likely that the enzymatic function of the protein with p.G332E is severely impaired. CONCLUSION: These are the first FUCA1 mutations identified in Tunisia that cause the fucosidosis disease. Bioinformatics analysis allowed us to establish an approximate structure-function relationship for the FUCA1 protein, thereby providing better genotype/phenotype correlation knowledge.

Contribution of common CFTR variants (M470V, T854, and Q1463) to cystic fibrosis in Tunisia: haplotype analysis.

BACKGROUND & OBJECTIVES: Cystic fibrosis (CF) is caused by mutations in the gene encoding the CF transmembrane regulator (CFTR) protein, a chloride channel located in the epithelial cell membrane. Over than 2,000 CFTR mutations have been identified, which contribute to the variety of clinical phenotypes of CF. We performed a case-control study to determine p.Met470Val (M470V), p.Thr854= (T854) and p.Gln1463= (Q1463) polymorphisms frequencies in CF patients and healthy controls and to elaborate haplotype based on these SNPs. METHODS: The genotyping of M470V (exon 10), T854 (exon 14a), and Q1463 (exon 24) variants were identified using polymorphism restriction fragment length polymorphism (RFLP). RESULTS & CONCLUSION: Statistical difference was noted in the genotype distribution of two markers, M470V and T854, between CF and control groups. However, the Q1463 polymorphism is not identified in two studied groups. Three haplotypes were found in CF patients and controls. An exclusive association between the ancestral haplotype 1-1-2 and p.Phe508del (F508del) mutation was shown. In Tunisia, this is the first work to be interested in the analysis of M470V, T854 and Q1463 polymorphisms and haplotypes associated with the most common mutation, F508del, in the Tunisian population and worldwide.

Nonketotic Hyperglycinemia in Tunisia. Report upon a Series of 69 Patients.

AIM: The aim of the study is to report on epidemiological, clinical, and biochemical characteristics of nonketotic hyperglycinemia (NKH) in Tunisia. METHODS: Patients diagnosed with NKH in Laboratory of Biochemistry at Rabta hospital (Tunis, Tunisia) between 1999 and 2018 were included. Plasma and cerebrospinal fluid (CSF) free amino acids were assessed by ion exchange chromatography. Diagnosis was based on family history, patient's clinical presentation and course, and increased CSF to plasma glycine ratio. RESULTS: During 20 years, 69 patients were diagnosed with NKH, with 25 patients originating from Kairouan region. Estimated incidences were 1:55,641 in Tunisia and 1:9,684 in Kairouan. Consanguinity was found for 73.9% of the patients and 42% of the families have history of infantile death due to a disease of similar clinical course than the propositus. Clinical symptoms initiated within the first week of life in 75% of the patients and within the first 3 months in 95.7% ones. The phenotype was severe in 76.8% of the patients. Main symptoms were hypotonia, feeding difficulties, coma, apnea, and seizures. Most patients died within few days to months following diagnosis. CSF to plasma glycine ratio was increased in all patients. CSF and plasma glycine levels were negatively correlated with age of disease onset and severity. CONCLUSION: NKH is quite frequent in Tunisia. Kairouan region has the highest NKH incidence rate, worldwide. However, due to lack of confirmatory enzymatic and genetic tests, NKH diagnosis was based on first-line biochemical tests. Characterization of causal mutations is needed for accurate diagnosis and prenatal diagnosis of this devastating life-threatening disease.

Morning specimen is not representative of metabolic control in Tunisian children with phenylketonuria: a repeated cross-sectional study.

Objective and methods To evaluate variation of capillary phenylalanine concentrations over the day in patients treated for phenylketonuria and the reliability of the morning sample to assess metabolic control, we conducted a repeated cross-sectional study in 25 Tunisian patients on phenylalanine-low diet. For each patient, we collected nine capillary samples over the day. Phenylalanine was dosed by fluorimetry. Results There was a wide variability of phenylalanine concentrations over the day (p<0.001). Compared to morning sample, phenylalanine concentration was significantly lower before lunch (p=0.038), after lunch (p=0.025), before dinner (p<0.001), after dinner (p=0.035) and at 4:00 a.m. (p=0.011). Compared to the 24 h sampling, the morning sample had a 68% to identify unbalanced patients. 60% of patients, had peak phenylalanine concentration after the morning. Half of the patients with normal morning phenylalanine concentration had low phenylalanine values over 8-20 h. Percentages of high phenylalanine concentrations over the last semester were higher in patients with poor metabolic control over the 24 h (21% ± 43 vs. 0% ± 9%); p=0.043. Conclusion A single morning sample gives an incomplete information on metabolic control in phenylketonuric patients. Using four pre-prandial samples on the day should be considered as alternative in patients with good metabolic control.

Quality of life and associated factors in parents of children with late diagnosed phenylketonuria. A cross sectional study in a developing country (Tunisia).

Objectives We investigated the quality of life (QOL) in parents of children with late treated phenylketonuria (PKU) and its associated factors. Methods We conducted a cross sectional study in the reference center of inherited metabolic disease in Tunisia. We used the Tunisian version of the 36-item short-form health survey questionnaire (SF-36). We compared variables in the groups with and without impaired QOL and the SF-36 scores between subgroups of parents and children and between our sample and the Tunisian general population based on published data. We looked for associations between SF-36 scores and quantitative variables. Linear regression and logistic binary regression were used for multivariate analysis. Results Sixty-five parents from 42 families participated. QOL was impaired in 61% of them. The mean SF-36 score was 55.3 ± 25.07. The physical component sub-score was higher than that reported in the Tunisian general population (63.66 ± 27.77 vs. 50.11 ± 8.53; p<0.001). The mental component sub-score was comparable to that reported in the Tunisian general population (46.99 ± 25.94 vs. 47.96 ± 9.82; p=0.830). Gender (mothers) (p=0.008), low monthly income (p = 0.027), low education (p=0.011), and autism in PKU children (p = 0.001) were associated with impaired QOL. Conclusions We identified at risk parents for altered quality of life among parents of PKU children. Our findings were used to develop a psychological and social support strategy for at-risk parents and to promote the implementation of newborn screening of this treatable disease in our low-income country.

Hemophagocytic Lymphohistiocytosis: A Rare Complication of an Ultrarare Lysosomal Storage Disease.

Hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening hyperinflammatory condition that may be triggered by infections, autoimmune and immunologic disorders, malignancies, and metabolic diseases. Early and accurate diagnosis of HLH and its underlying cause is of paramount importance for proper management and prognosis. We report the case of a Tunisian 21-month-old girl who initially presented clinical features of HLH related to a lysosomal acid lipase deficiency. The genetic sequence analysis of the LIPA gene revealed a never described homozygous mutation c.966G>C (p.Gln322His). The parents were heterozygous for this mutation. Enzyme replacement therapy was not provided for the patient. She received etoposide, corticosteroids, and cyclosporine for the HLH. She is waiting for hematopoietic stem cell transplantation. To the best of our knowledge, this is the second Tunisian case of secondary HLH complicating lysosomal acid lipase deficiency related to a new homozygous mutation: c.966G>C (p.Gln322His).

Preliminary national report on cystic fibrosis epidemiology in Tunisia: the actual state of affairs.

AIM: To establish a preliminary national report on clinical and genetic features of cystic fibrosis (CF) in Tunisian children as a first measure for a better health care organization. METHODS: All children with CF diagnosed by positive sweat tests between 1996 and 2015 in children's departments of Tunisian university hospitals were included. Data was recorded at diagnosis and during the follow-up from patients' medical records. RESULTS: In 12 departments, 123 CF children were collected. The median age at diagnosis was 5 months with a median diagnosis delay of 3 months. CF was revealed mostly by recurrent respiratory tract infections (69.9%), denutrition (55.2%), and/or chronic diarrhea (41.4%). The mean sweat chloride concentration was 110.9mmol/L. At least one mutation was found in 95 cases (77.2%). The most frequent mutations were Phe508del (n=58) and E1104X (n=15). Fifty-five patients had a Pseudomonas Aeruginosa chronic colonization at a median age of 30 months. Cirrhosis and diabetes appeared at a mean age of 5.5 and 12.5 years respectively in 4 patients each. Sixty-two patients died at a median age of 8 months. Phe508del mutation and hypotrophy were associated with death (p=0.002 and p<0.001, respectively). CONCLUSION: CF is life-shortening in Tunisia. Setting-up appropriate management is urgent.

Role play for genetic counseling learning: Value and students perceptions.

BACKGROUND: Performing genetic counseling is one of the tasks of every paediatrician. This assumes prior training during the residency. AIM: To assess the impact of role-play (RP) for training of paediatric residents in genetic counseling and participants' perception. METHODS: Repetitive cross-sectional evaluation study. During two RP sessions, two residents played the role of the parents of a patient with cystic fibrosis, and another the role of the doctor. Residents had an evaluation by standardized patient exercises immediately before and after the session. Test scores were compared by the Wilcoxon rank test for associated samples. A satisfaction questionnaire was completed by the participants anonymously. RESULTS: Post-test scores were better than pre-test scores overall (p = 0.002) and for items in the cognitive domain (p = 0.002). Of the 12 participants, only one had had previous training in genetic counseling. All participants were satisfied with the learning and felt that it would change the way they practice. All participants thought they could do genetic counseling autonomously, but nine of them wanted to have other RP sessions on the same theme. Only one participant found the session stressful and all wanted to multiply this type of sessions for other learning. CONCLUSION: RP is an effective and well-accepted means for genetic counseling training. It should be integrated with paediatric resident training.

A severe clinical phenotype of Noonan syndrome with neonatal hypertrophic cardiomyopathy in the second case worldwide with RAF1 S259Y neomutation.

Noonan syndrome and related disorders are a group of clinically and genetically heterogeneous conditions caused by mutations in genes of the RAS/MAPK pathway. Noonan syndrome causes multiple congenital anomalies, which are frequently accompanied by hypertrophic cardiomyopathy (HCM). We report here a Tunisian patient with a severe phenotype of Noonan syndrome including neonatal HCM, facial dysmorphism, severe failure to thrive, cutaneous abnormalities, pectus excavatum and severe stunted growth, who died in her eighth month of life. Using whole exome sequencing, we identified a de novo mutation in exon 7 of the RAF1 gene: c.776C > A (p.Ser259Tyr). This mutation affects a highly conserved serine residue, a main mediator of Raf-1 inhibition via phosphorylation. To our knowledge the c.776C > A mutation has been previously reported in only one case with prenatally diagnosed Noonan syndrome. Our study further supports the striking correlation of RAF1 mutations with HCM and highlights the clinical severity of Noonan syndrome associated with a RAF1 p.Ser259Tyr mutation.

A Novel Mutation c.153 C>A in a Tunisian Girl With Wolman Disease and Unusual Presentation: Hemophagocytic Lymphohistiocytosis.

Wolman disease is an ultrarare lysosomal storage disease caused by a mutation in the LIPA gene. The clinical features of Wolman disease include early onset of vomiting, diarrhea, failure to thrive, hepatosplenomegaly, and bilateral adrenal calcification. We report the case of a 3-month-old infant who presented clinical features of hemophagocytic lymphohistiocytosis. Genetic sequence analysis of the LIPA gene revealed homozygous mutation c.153 C>A (p.Tyr51*). The parents were heterozygous for this mutation. Prenatal diagnosis has been carried out in the next pregnancy. To our knowledge, this mutation has never been reported before, and this is an unusual case of secondary hemophagocytic lymphohistiocytosis complicating Wolman disease.

Neuromuscular Involvement in Glycogen Storage Disease Type III in Fifty Tunisian Patients: Phenotype and Natural History in Young Patients.

BACKGROUND: Our aim was to describe the natural history of neuromuscular involvement (NMI) in glycogen storage disease type III (GSDIII). METHODS: We conducted a longitudinal study of 50 Tunisian patients, 9.87 years old in average. RESULTS: NMI was diagnosed at an average age of 2.66 years and was clinically overt in 85% of patients. Patients with clinical features were older (p = 0.001). Complaints were dominated by exercise intolerance (80%), noticed at 5.33 years in average. Physical signs, observed at 6.75 years in average, were dominated by muscle weakness (62%). Functional impairment was observed in 64% of patients, without any link with age (p = 0.255). Among 33 patients, 7 improved. Creatine kinase (CK) and aspartate aminotransferase (AST) levels were higher with age.Electrophysiological abnormalities, diagnosed in average at 6.5 years, were more frequent after the first decade (p = 0.0005). Myogenic pattern was predominant (42%). Nerve conduction velocities were slow in two patients. Lower caloric intake was associated with more frequent clinical and electrophysiological features. Higher protein intake was related to fewer complaints and physical anomalies. CONCLUSION: Neuromuscular investigation is warranted even in asymptomatic patients, as early as the diagnosis of GSDIII is suspected. Muscle involvement can be disabling even in children. Favorable evolution is possible in case of optimal diet.

High Frequency of Cardiovascular Complications in Tunisian Kawasaki Disease Patients: Need for a Further Awareness.

BACKGROUND: The outcome of Kawasaki disease (KD) depends on cardiovascular complications (CVCs). OBJECTIVES: This study aimed to explore diagnostic features and CVCs in Tunisian patients with KD. METHODS: In total, 33 Tunisian patients (age, 2.9 ± 2.2 years) fulfilling the diagnosis criteria of KD, were retrospectively reviewed. Nonparametric tests were used to compare the two groups with regards to coronary complications (CCs). RESULTS: Diagnosis of KD was established at day 11 ± 5.1 from the beginning of the fever. Apyrexia was obtained in an average of 29 h after completion of intravenous immunoglobulin. CVCs were identified in 52% of cases: CC in 15 patients (giant aneurysm >8 mm in five patients) and non-CCs in 6 patients (severe in three patients). CCs were more frequently associated with the male sex (p = 0.037), fever lasting >8 days (p = 0.028) and longer time to apyrexia (p = 0.031). CONCLUSION: In Tunisia, better knowledge and monitoring of KD are warranted.

Patient-management Problem (PMP) for paediatrics learning: Value and students perceptions.

BACKGROUND: The use of the pedagogic tool Patient-Management Problem (PMP) for medical teaching and evaluation remains limited in Tunisia. AIM: to evaluate the value of PMP learning sessions in pediatrics and students' perception of the use of PMP for learning and evaluation. METHODS: We conducted a cross-sectional evaluative study in four pediatric departments in Tunis. Students had a learning session with an electronic PMP. Their knowledge was assessed using a pre-test and a post-test. Their perception of the learning was assessed using a questionnaire. RESULTS: Forty-four students participated. The post-test scores were statistically higher than those of the pre-test (p <0.001). More than 90% of the students, found that the PMP was a useful learning tool, which would change their way of thinking and agreed to its regular use for teaching. 86% of students declared that the PMP were better than other means of learning and 79% that PMP was a reliable assessment tool, but 75% believed it was more stressful than other means of assessment. The degree of satisfaction with previous PMP experience was negatively correlated with perception of reliability (p = 0.043), impact on clinical reasoning (p = 0.044), and PMP being better than the other learning means (p = 0.044). CONCLUSION: The PMP is an effective learning tool and is well accepted by students. Its use should be generalized to all disciplines for teaching and evaluation. Further trainings are necessary for medical teachers to guarantee quality PMPs.

Correction to: Full title: peripheral venous catheter complications in children: predisposing factors in a multicenter prospective cohort study.

Following publication of the original article [1], one of the authors flagged that the title of the article was submitted (incorrectly) with "Full title:" at the beginning.