Ergul Tuncbilek

Mutations in the Gene Encoding the RER Protein FKBP65 Cause Autosomal-Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta is a clinically and genetically heterogeneous brittle bone disorder that results from defects in the synthesis, structure, or posttranslational modification of type I procollagen. Dominant forms of OI result from mutations in COL1A1 or COL1A2, which encode the chains of the type I procollagen heterotrimer. The mildest form of OI typically results from diminished synthesis of structurally normal type I procollagen, whereas moderately severe to lethal forms of OI usually result from structural defects in one of the type I procollagen chains. Recessively inherited OI, usually phenotypically severe, has recently been shown to result from defects in the prolyl-3-hydroxylase complex that lead to the absence of a single 3-hydroxyproline at residue 986 of the alpha1(I) triple helical domain. We studied a cohort of five consanguineous Turkish families, originating from the Black Sea region of Turkey, with moderately severe recessively inherited OI and identified a novel locus for OI on chromosome 17. In these families, and in a Mexican-American family, homozygosity for mutations in FKBP10, which encodes FKBP65, a chaperone that participates in type I procollagen folding, was identified. Further, we determined that FKBP10 mutations affect type I procollagen secretion. These findings identify a previously unrecognized mechanism in the pathogenesis of OI.

Implications of certain genetic polymorphisms in scarring in vesicoureteric reflux: Importance of ace polymorphism

Polymorphisms of the renin-angiotensin system (RAS) have been shown to affect renal prognosis in a number of diseases. We examined the influence of deletion (D) and insertion (I) polymorphism in the angiotensin I-converting enzyme (ACE) gene and the other polymorphic markers of RAS, and that of plasminogen-activator inhibitor-1 (PAI-1) on renal scarring in reflux nephropathy. Ninety-four children with third- or fourth-degree reflux were the subject of the study. They were stratified into two groups according to the technetium-99m-dimercaptosuccinic acid (DMSA) findings: the first group consisted of 41 patients with no scar formation. In the second group (n = 53), there was significant scar formation in the refluxing units. ACE levels, ACE gene, angiotensin-1 receptor (AT1) A1166C, angiotensinogen (ATG) M235T, and PAI-1 4G/5G polymorphisms were studied. In the second group with scarred kidneys, 18 patients had decreased renal function. The frequency of patients homozygous for the D allele was significantly greater in the second group with scar formation in the refluxing units compared with the first group of patients (P < 0.005). On multivariate analysis, the DD genotype was the only factor that had a significant impact on renal scar formation, introducing a 4.9-fold risk (P < 0.05, 95% confidence interval). We were unable to find any correlation with the presence ofDD genotype and hypertension, decreased renal function, proteinuria, or sex of the patient. DDgenotype correlated with the serum ACE levels (P < 0.005). AT1and ATGpolymorphisms and PAI-1 polymorphism did not correlate with scar formation or any of the parameters. This study provides evidence that the DDgenotype of ACE may be a genetic susceptibility factor contributing to adverse renal prognosis in reflux nephropathy; namely, scar formation. The role of the synergism between the aforementioned genetic polymorphisms can be enlightened with larger patient groups, possibly through multicenter studies.

Methylenetetrahydrofolate reductase enzyme polymorphisms as maternal risk for Down syndrome among Turkish women

Advanced maternal age is the only fully accepted risk factor for trisomy 21, while most children with Down syndrome (DS) are born to younger mothers (<35 years). The relationship between chromosomal nondisjunction leading to aneuploidy and folate metabolism has drawn attention in the recent years. In this study, we examined the two polymorphisms in genes encoding the folate metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR), namely, 677C > T and 1298A > C. The prevalence of these variant genotypes in mothers of DS children (case mothers) (n = 152) was compared with controls (n = 91). Frequencies of MTHFR 677C > T genotypes (CC, CT, and TT) and also combination of heterozygous and homozygous variant genotypes (CT or TT) (P = 0.28) demonstrated no difference between the case and control groups. Genotype frequencies of MTHFR 1298A > C (AA, AC, and CC) were similar among the case and control mothers. Variant genotypes of MTHFR 1298A > C (AC or CC) were also insignificant when compared between the two groups. This is yet the largest case‐control study conducted for MTHFR 677C > T and also the first to investigate a possible relation with MTHFR 1298A > C. The data presented in this study fail to support the relationship between MTHFR 677C > T and 1298A > C polymorphisms and risk of having a child with DS.

High frequency hearing loss in Ullrich-Turner syndrome

Abstract A total of 38 patients with Ullrich-Turner syndrome underwent standard otological and audiometric evaluation as well as high frequency audiological tests. Some 26 (68.4%) patients had a history of middle ear infections, and ten (26.3%) had required otolaryngological surgery. Conventional audiometry (125–8000 Hz) demonstrated normal hearing in only 25 of the ears (33%); between 500–4000 Hz, 16 ears (21.0%) had a mixed type and eight ears (10.5%) had conductive hearing loss. High frequency audiometry (8–18 kHz) revealed sensorineural hearing loss in 98.7% of the ears. Our results for conventional audiometry are in accordance with the literature. Conclusion The detection of a high prevalence of hearing loss in the high frequency range brings a significant new perspective to the pursuit of the aetiology of ear and hearing problems in Ullrich-Turner syndrome. This pathology seems to be a premature variant of presbycusis and it may underlie future hearing impairment which will come to clinical attention only after it progresses to conventional testing frequencies. While further studies are underway to evaluate this aspect, routine otological and audiological follow-up of patients with Ullrich-Turner syndrome is warranted from the time of diagnosis.

Bilateral Poland anomaly

Bilateral absence of the pectoralis major muscle with accompanying abnormalities of shoulder muscles has been reported in patients without Poland anomaly (PA). However, symmetric absence of pectoralis major muscles, hypoplasia of breasts and nipples with symmetric chest wall deformity and bilateral hand anomaly has not previously been reported. A 6-year-old girl with bilateral absence of pectoralis major muscles and hand involvement and symmetric chest wall deformity is, to our knowledge, the first known case of bilateral Poland anomaly.

Association of the 677C-->T mutation on the methylenetetrahydrofolate reductase gene in Turkish patients with neural tube defects.

We report the analysis of the 677C→T mutation on the 5,10-methylenetetrahydrofolate reductase gene in Turkish controls and cases of neural tube defects. Mutation analysis of 91 patients with neural tube defects, 72 mothers, 63 fathers, and 93 healthy controls has been made by polymerase chain reaction and allele specific restriction digestion with Hinf I. We did not find a significant difference in the 677C→T allele and genotype distribution among the patients with neural tube defects, their parents, and the control group. This result suggests that another mutation in the folate-related enzyme genes could be responsible for neural tube defects in Turkey. None of the mothers of patients with neural tube defects was advised to use folic acid as recommended to prevent neural tube defects. An immediate attempt to establish an education program for healthcare providers and women of childbearing age is crucial in Turkey. Furthermore, fortification of foods with folate would be a better approach. (J Child Neurol 1999;14:159-161).

Is Dandy–Walker malformation associated with “distal 13q deletion syndrome”? Findings in a fetus supporting previous observations

We report on a fetus with a large deletion of the distal part of the long arm of chromosome 13, (del(13)(q14 → qter)) congenital anomalies of the urinary system, lungs and extremities, and Dandy–Walker malformation (DWM). Although DWM has been associated with many chromosomal abnormalities and genetic syndromes, its relation to the distal 13q has been demonstrated recently. In 2002, McCormack et al., described two patients with deletions of the long arm of chromosome 13 who had multiple congenital abnormalities along with holoprosencephaly (HPE) and DWM. The phenotypic features and autopsy findings of a fetus with “distal 13q deletion syndrome” at 22 weeks gestation are discussed and comparison with the previous two cases is made. The findings support the previous hypothesis suggesting that haploinsufficiency at a locus within 13q22‐33 due to microdeletions may be responsible for isolated DWM in some of the patients. Detailed examination of 13q (13q22‐33) by means of conventional and molecular cytogenetic methods is necessary in cases with DWM.

Benefit of high-dose methylprednisolone in comparison with conventional-dose prednisolone during remission induction therapy in childhood acute lymphoblastic leukemia for long-term follow-up.

Eight-year event-free survival (EFS) was evaluated in 205 patients with acute lymphoblastic leukemia (ALL), to consider the efficacy of high-dose methylprednisolone (HDMP) given during remission induction chemotherapy between 1 and 29 days. The St Jude Total XI Study protocol was used after some minor modifications in this trial. Patients were randomized into two groups. Group A (n = 108) received conventional dose (60 mg/m2/day orally) prednisolone and group B (n = 97) received HDMP (Prednol-L, 900–600 mg/m2 orally) during remission induction chemotherapy. Complete remission was obtained in 95% of the 205 patients who were followed-up for 11 years; median follow-up was 72 months (range 60–129) and 8-year EFS rate was 60% overall (53% in group A, 66% in group B). The EFS rate of group B was significantly higher than of group A (P = 0.05). The 8-year EFS rate of groups A and B in the high-risk groups was 39% vs 63% (P = 0.002). When we compared 8-year EFS rate in groups A and B in the high-risk subgroup for both ages together ⩽2 or ⩾10 years, it was 44% vs 74%, respectively. Among patients in the high-risk subgroup with a WBC count ⩾50 × 109/l, the 8-year EFS was 38% in group A vs58% in group B. During the 11-year follow-up period, a total of 64 relapses occurred in 205 patients. In group A relapses were higher (39%) than in group B (23%) (P = 0.05). These results suggest that HDMP during remission-induction chemotherapy improves the EFS rate significantly for high-risk patients in terms of the chances of cure.

Evaluation of children with myelodysplastic syndrome: importance of extramedullary disease as a presenting symptom.

Thirty-three children diagnosed with primary myelodysplastic syndrome (MDS) in a single institution over an 8 year period were evaluated with special emphasis on children who presented with extramedullary disease (EMD). EMD was present at diagnosis in 12 (36%) of the 33 children with MDS. Three patients with juvenile myelomonocytic leukemia (JMML) and 2 patients with chronic myelomonocytic leukemia (CMML) presented with pleural effusion. Pericardial effusion was present in 3 of these patients, two of whom also had thrombosis. Pyoderma gangrenosum, relapsing polychondritis were the initial findings in another two cases with JMML. Lymphadenopathy (n=1), gingival hypertrophy (n=2), orbital granulocytic sarcoma (n=1) and spinal mass (n=1) were the presenting findings in 5 patients with refractory anemia with excess of blasts in transformation. Since high-dose methylprednisolone (HDMP, 20–30 mg/kg/day) has been shown to induce differentiation and apoptosis of myeloid leukemic cells in children with different morphological subtypes of acute myeloid leukemia in vivo and in vitro, 25 children with de novo MDS were treated with combined HDMP and cytotoxic chemotherapy. Dramatic improvement of EMD and decrease in blast cells both in the peripheral blood and bone marrow were obtained following administration of short-course HDMP treatment alone as observed in children with AML. HDMP, combined with low-dose cytosine arabinoside and mitoxantrone were used for the remission induction. Remission was achieved in 8 (80%) of 10 children who presented with EMD and in 9 (60%) of 15 children without EMD. Long-term remission (>6 years) was obtained in 4 (two with JMML and two with CMML), three of whom presented with EMD. In conclusion EMD can be a presenting finding in childhood MDS as observed in adults. In addition, the beneficial effect of HDMP combined with more intensive chemotherapy should be explored as alternative therapy in children with MDS not suitable for bone marrow transplantation.

Homozygous FGF3 mutations result in congenital deafness with inner ear agenesis, microtia, and microdontia

Homozygous mutations in the fibroblast growth factor 3 (FGF3) gene have recently been discovered in an autosomal recessive form of syndromic deafness characterized by complete labyrinthine aplasia (Michel aplasia), microtia, and microdontia (OMIM 610706 – LAMM). In order to better characterize the phenotypic spectrum associated with FGF3 mutations, we sequenced the FGF3 gene in 10 unrelated families in which probands had congenital deafness associated with various inner ear anomalies, including Michel aplasia, with or without tooth or external ear anomalies. FGF3 sequence changes were not found in eight unrelated probands with isolated inner ear anomalies or with a cochlear malformation along with auricle and tooth anomalies. We identified two new homozygous FGF3 mutations, p.Leu6Pro (c.17T>C) and p. Ile85MetfsX15 (c.254delT), in four subjects from two unrelated families with LAMM. The p.Leu6Pro mutation occurred within the signal site of FGF3 and is predicted to impair its secretion. The c.254delT mutation results in truncation of FGF3. Both mutations completely co‐segregated with the phenotype, and heterozygotes did not have any of the phenotypic findings of LAMM. Some affected children had large skin tags on the upper side of the auricles, which is a distinctive clinical component of the syndrome. Enlarged collateral emissary veins associated with stenosis of the jugular foramen were noted on computerized tomographies of most affected subjects with FGF3 mutations. However, similar venous anomalies were also detected in persons with non‐syndromic Michel aplasia, suggesting that a direct causative role of impaired FGF3 signaling is unlikely.