K. Monastiri

Influence of combined CYP3A4 and CYP3A5 single-nucleotide polymorphisms on tacrolimus exposure in kidney transplant recipients: a study according to the post-transplant phase

AIM The present study investigated in Tunisian renal transplant patients, genetic polymorphisms of CYP3A4 -392A>G and CYP3A5 6986A>G and their influence on tacrolimus (Tac) pharmacokinetics during early and late post-transplant (PT) phases and established customized ranges of Tac doses matching the C0 target levels according to CYP3A4 and CYP3A5 genotype combination and the PT phase. PATIENTS & METHODS We included adult Tunisian patients having received Tac for de novo kidney grafts and undergone a therapeutic drug monitoring of Tac by morning C0 monitoring during early (1 to 90 days) and late (over 90 days) PT phases. The genomic DNA was extracted from peripheral blood mononuclear cells using a salting-out procedure. CYP3A4 promoter (rs2740574; -392A>G) and CYP3A5 (rs776746; 6986A>G) SNP genotyping was analyzed using PCR-RFLP. RESULTS Fifty-two patients were enrolled in the study. During the early PT phase, the CYP3A5 polymorphism but not that of CYP3A4, correlates significantly with Tac dose-normalized C0 (C0/D ratio). During the late PT phase, the effect of CYP3A4 polymorphism becomes significant and that of CYP3A5 becomes nonsignificant on Tac C0/D Tac. The mean daily doses (mg/kg) matching therapeutic C0, regardless of the CYP3A genotypes, were 0.16 ± 0.05 and 0.10 ± 0.05 during early and late PT phase, respectively. Carriers of the CYP3A4*1B allele require higher doses to maintain the C0 in the therapeutic range during the two PT phases. However, patients carrying the CYP3A5*1 require significant higher Tac doses, only during the early phase. CONCLUSION Our data support a critical role of the CYP3A5 6986A>G and CYP3A4 -392A>G polymorphisms on the variation of Tac exposure during the early and the late PT phase, respectively. The establishment of customized Tac doses, according to CYP3A4/CYP3A5 genotype combination and the PT time, may allow preventing graft rejection and improving the safety profile of this drug. Further studies are needed to investigate this issue.

A novel CASR mutation in a Tunisian FHH/NSHPT family associated with a mental retardation

The calcium-sensing receptor (CASR), a plasma membrane G-protein coupled receptor, is expressed in parathyroid gland and kidney, and controls systemic calcium homeostasis. Inactivating CASR mutations have previously been identified in patients with familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT). The aim of the present study is to determine the underlying molecular defect of FHH/NSHPT disease in a consanguineous Tunisian family. Mutation screening was carried out using RFLP-PCR and direct sequencing. We found that the proband is homozygous for a novel 15 bp deletion in the exon 7 (c.1952_1966del) confirming the diagnosis of NSHPT. All the FHH members were found to be heterozygous for the novel detected mutation. The mutation, p.S651_L655del, leads to the deletion of 5 codons in the second trans-membrane domain of the CASR which is thought to be involved in the processes of ligand-induced signaling. This alteration was associated with the evidence of mental retardation in the FHH carriers and appears to be a novel inactivating mutation in the CASR gene. Our findings provide additional support for the implication of CASR gene in the FHH/NSHPT pathogenesis.

Sanjad-Sakati syndrome in a Tunisian child

Sanjad-Sakati syndrome (SSS) (OMIM 241410) is a rare autosomal recessive disorder characterized by congenital hypoparathyroidism with growth and mental retardation associated with seizures and a characteristic physiognomy. SSS molecular pathology has been shown to be due to mutations in the TBCE gene on chromosome 1q42-q43. All affected patients of Arab origin are homozygous for a 12-bp (155-166del) deletion in exon 3 of this gene. We report on a Tunisian child with SSS who was homozygous for the 155-166del mutation. Our findings provide additional support of the common (155-166del) deletion founder effect in exon 3 of the TBCE gene in Arab patients. It is very likely that this mutation originated in the Middle East and was introduced in Tunisia by the Banu Hilal invaders.

Homogénéité mutationnelle de la glycogénose de type Ia en Tunisie.

The glycogen storage disease type Ia (GSD Ia) is a rare inherited disorder, with autosomal recessive determinism. It is characterized by hepatomegaly, short stature and hypoglycemia with lactic acidemia. The confirmation of diagnosis is based on the enzymatic assay performed on liver biopsy. For Tunisians patients, this biochemical test is performed abroad. The aim of our study is the molecular characterization of GSD Ia in Tunisian patients and the development of a molecular diagnosis tool. Our study included 27 patients from 23 unrelated families, mutation analysis revealed that the R83C mutation is the most frequent (65%, 30/46 mutant alleles), followed by the R170Q mutation (30%, 14/46 mutant alleles). The homogeneity of mutation spectrum of GSD Ia in Tunisia allows the development of a cost effective and reliable tool for the confirmation of clinical diagnosis among suspected GSD Ia patients.

Spontaneous Intestinal Perforation in a Very Low Birth Weight Infant: Successful Management by Peritoneal Needle Suction

The baby was born at 27 weeks gestation to a 31year-old mother by normal vaginal delivery. Birth weight was 1370 grams and Apgar scores were 9 at one minute and 10 at five minutes. He was admitted to the neonatal intensive care unit for respiratory distress syndrome requiring continuous positive airway pressure (CPAP) support. On the second day of hospital stay, although the general condition of the baby was stable, he developed abdominal distension. However, there was no erythema, tenderness or, a palpable lump. Abdominal X-ray revealed pneumoperitoneum, with free gas under both the domes of diaphragm (Fig.1A).

Clinical profile of comorbidity of rare diseases in a Tunisian patient: a case report associating incontinentia pigmenti and Noonan syndrome

BackgroundNoonan syndrome (NS) is an autosomal dominant multisystem disorder caused by the dysregulation of several genes belonging to the RAS Mitogen Activated Protein Kinase (MAPK) signaling pathway. Incontinentia Pigmenti (IP) is an X-linked, dominantly inherited multisystem disorder.Case presentationThis study is the first report of the coexistence of Noonan (NS) and Incontinentia Pigmenti (IP) syndromes in the same patient. We report on the clinical phenotype and molecular characterization of this patient. The patient was examined by a pluridisciplinary staff of clinicians and geneticist. The clinical diagnosis of NS and IP was confirmed by molecular investigations. The newborn girl came to our clinics due to flagrant dysmorphia and dermatological manifestations. The clinical observations led to characterize the Incontinentia Pigmenti traits and a suspicion of a Noonan syndrome association. Molecular diagnosis was performed by Haloplex resequencing of 29 genes associated with RASopathies and confirmed the NS diagnosis. The common recurrent intragenic deletion mutation in IKBKG gene causing the IP was detected with an improved PCR protocol.ConclusionThis is the first report in the literature of comorbidity of NS and IP, two rare multisystem syndromes.

ABCB1 and SLCO1B3 Gene Polymorphisms and Their Impact on Digoxin Pharmacokinetics in Atrial Fibrillation Patients among the Tunisian Population.

Background: Digoxin is a substrate of P-glycoprotein (P-gp) and organic anion transporting polypeptide transporters that are encoded by ABCB1 and SLCO1B3 genes. Genetic polymorphisms in both genes may explain inter-individual variability of serum digoxin concentration (SDC). This study evaluates the possible effect of the most common ABCB1 and SLCO1B3 polymorphisms on SDC after a single oral dose of digoxin in Tunisian atrial fibrillation (AF) patients. Methods:ABCB1 and SLCO1B3 genotypes were analyzed in 102 patients with AF who received digoxin (0.5 mg) without (group I, n = 58) or with the co-administration of P-gp inhibitors (group II, n = 44). SDCs were determined at 6 h following the oral dose. Results: SDCs levels were significantly higher in patients who were co-administered P-gp inhibitors. No influence was noted in ABCB1 and SLCO1B3 polymorphisms on SDC in group I patients. However, SDCs values were significantly different among ABCB1 single nucleotide polymorphisms (SNPs) genotypes of 2677G>T/A (TT, GG>GT, p < 0.05) and 3435C>T (TT, CC>CT, p < 0.05) only in group II with no effect of 1236C>T and SLCO1B3 SNPs. Conclusion: Results suggest that P-gp inhibitors and ABCB1 gene polymorphisms may affect digoxin pharmacokinetics.

Further Evidence for the Implication of LZTR1 , a Gene not Associated with the Ras-Mapk Pathway, in the Pathogenesis of Noonan Syndrome

Background: Noonan Syndrome (NS) is a relatively common autosomal dominant condition, caused by germline mutations in different genes involved in the RAS MAP Kinase signaling pathway. Although clinically heterogeneous, characteristic findings include typical facial features, short stature, chest deformity and congenital heart diseases. Methods: Here, we present the clinical and molecular characterization of a Tunisian patient with NS. A comprehensive mutations analysis of 29 genes belonging to the RAS pathway or encoding for interactors was performed, using targeted next generation sequencing. Results: The results revealed a novel pathogenic substitution affecting the LZTR1, whose mutations have been described only in 5 cases of NS. Conclusion: This report supports the implication of LZTR1 in Noonan syndrome. Next Generation Sequencing seems a suitable method for mutation detection in clinically and genetically heterogeneous syndromes such as NS.

Détresse respiratoire révélant un corps étranger intra-œsophagien chez un nouveau-né

Ce nouveau-né âgé de 7 jours, cadet d’une fratrie de 3 enfants âgés de 1 à 4 ans, a été amené par ses parents pour une cyanose avec gêne respiratoire d’apparition aiguë. Il était né par césarienne et allaité exclusivement au sein. L’interrogatoire a révélé une faille dans la surveillance, le nouveau-né étant resté seul avec ses 3 frères pendant quelques minutes. L’aı̂né a rapporté avoir pulvérisé dans la gorge de son frère un spray cicatrisant appartenant à la maman. À l’admission, le nouveau-né était polypnéique (60 cycles/min) sans signes de lutte respiratoire et sa saturation transcutanée en oxygène (SaO2) était à 74 %. À l’examen il n’y avait ni corps étranger dans la gorge ni traces de traumatisme de la cavité buccale mais une muqueuse d’aspect irrité. Le reste de l’examen somatique était sans particularité. La radiographie du thorax de face était normale. Le diagnostic d’infection virale étant peu probable en raison de l’installation aiguë de la symptomatologie et de l’absence de contage viral, une inflammation de l’oropharynx secondaire à l’application du spray a été le diagnostic initialement retenu. Le nouveau-né a été perfusé et des lunettes nasales à haut débit ont été installées avec une fraction inspirée en oxygène (FiO2) à 25 %, ce qui a permis la normalisation de la SaO2. Une radiographie de thorax a été réalisée deux jours plus tard devant la persistance de la symptomatologie respiratoire (fig. 1). L’hypersialorrhée et la survenue d’accès de cyanose à chaque tentative d’alimenta-

Pericardial effusion with cardiac tamponade caused by a central venous catheter in a very low birth weight infant

With more and more extreme premature and very low-birth weight babies being resuscitated, umbilical central venous catheterisation is now being used more frequently in neonatal intensive care. One of the life-threatening complications is pericardial effusion and cardiac tamponade; however, it is potentially reversible when it is caught in time. The authors present a case of cardiac tamponade following umbilical venous catheterisation in a neonate. The patient was diagnosed at the appropriate time by echocardiography and urgent pericardiocentesis proved lifesaving.