Bülent Hacıhamdioğlu

22q11 deletion syndrome: current perspective

Chromosome 22q11 is characterized by the presence of chromosome-specific low-copy repeats or segmental duplications. This region of the chromosome is very unstable and susceptible to mutations. The misalignment of low-copy repeats during nonallelic homologous recombination leads to the deletion of the 22q11.2 region, which results in 22q11 deletion syndrome (22q11DS). The 22q11.2 deletion is associated with a wide variety of phenotypes. The term 22q11DS is an umbrella term that is used to encompass all 22q11.2 deletion-associated phenotypes. The haploinsufficiency of genes located at 22q11.2 affects the early morphogenesis of the pharyngeal arches, heart, skeleton, and brain. TBX1 is the most important gene for 22q11DS. This syndrome can ultimately affect many organs or systems; therefore, it has a very wide phenotypic spectrum. An increasing amount of information is available related to the pathogenesis, clinical phenotypes, and management of this syndrome in recent years. This review summarizes the current clinical and genetic status related to 22q11DS.

Clinical and radiographic findings in two brothers affected with a novel mutation in matrix metalloproteinase 2 gene.

The two well-described osteolysis syndromes associated with matrix metalloproteinase-2 deficiency and mutations in the metalloproteinase-2 gene are Torg–Winchester syndrome and nodulosis–arthropathy–osteolysis variant. They are characterized by carpal–tarsal destruction, subcutaneous nodules, and generalized osteoporosis and show autosomal recessive inheritance. Herein, we report two siblings affected with a novel mutation in matrix metalloproteinase 2 gene and discuss their clinical and radiographic findings.

Sphingosine-1-phosphate lyase mutations cause primary adrenal insufficiency and steroid-resistant nephrotic syndrome

Primary adrenal insufficiency is life threatening and can present alone or in combination with other comorbidities. Here, we have described a primary adrenal insufficiency syndrome and steroid-resistant nephrotic syndrome caused by loss-of-function mutations in sphingosine-1-phosphate lyase (SGPL1). SGPL1 executes the final decisive step of the sphingolipid breakdown pathway, mediating the irreversible cleavage of the lipid-signaling molecule sphingosine-1-phosphate (S1P). Mutations in other upstream components of the pathway lead to harmful accumulation of lysosomal sphingolipid species, which are associated with a series of conditions known as the sphingolipidoses. In this work, we have identified 4 different homozygous mutations, c.665G>A (p.R222Q), c.1633_1635delTTC (p.F545del), c.261+1G>A (p.S65Rfs*6), and c.7dupA (p.S3Kfs*11), in 5 families with the condition. In total, 8 patients were investigated, some of whom also manifested other features, including ichthyosis, primary hypothyroidism, neurological symptoms, and cryptorchidism. Sgpl1–/– mice recapitulated the main characteristics of the human disease with abnormal adrenal and renal morphology. Sgpl1–/– mice displayed disrupted adrenocortical zonation and defective expression of steroidogenic enzymes as well as renal histology in keeping with a glomerular phenotype. In summary, we have identified SGPL1 mutations in humans that perhaps represent a distinct multisystemic disorder of sphingolipid metabolism.

The clinical and genetic heterogeneity of mixed gonadal dysgenesis: does “disorders of sexual development (DSD)” classification based on new Chicago consensus cover all sex chromosome DSD?

Clinical findings illustrate the wide spectrum of the phenotypic manifestations of 45,X/46,XY mosaicism in the sex chromosome disorders of sex differentiation (DSD). The objective of study is to evaluate the characteristics of 45,X/46,XY patients and questioning of their place within the DSD categorization. The clinical findings of 11 patients with 45,X/46,XY mosaicism are described including the presentation, gonadal morphology, genital anatomy, and the hormone levels among 285 patients with DSD evaluated. Sixty-seven patients were diagnosed with sex chromosome DSD (50 Turner, three Klinefelter, ten 45,X/46,XY gonadal disgenesis, one 45X/46,XY ovotesticular DSD, one 47,XYY ovotesticular DSD, and two 46,XX/46,XY ovotesticular DSD). The type and the percentage of patients with 45,X/46,XY mosaicism were as follows: Four cases of mix gonadal dysgenesis, four cases of partial gonadal dysgenesis, two cases of complete gonadal dysgenesis, one case of ovotesticular DSD. On the other hand, another patient that has 45,X/46,XX mosaicism was diagnosed with MGD with the presence of the streak gonad on the right side and the testis on the other side. Conclusion: We suggest that sex chromosome DSD categorization can include 45,X/46,XY PGD and 45,X/46,XY CGD. Mixed gonadal dysgenesis may be also placed among the disorders of testicular differentiation of 46,XY DSD subdivision.

Clinical characteristics of recessive and dominant congenital hyperinsulinism due to mutation(s) in the ABCC8/KCNJ11 genes encoding the ATP-sensitive potasium channel in the pancreatic beta cell

Abstract Background: Recessive mutations in ABCC8/KCNJ11 of β-cell KATP channel generally cause severe medically unresponsive hyperinsulinemic hypoglycemia (HH). Rarer dominant mutations in these genes have been described that mostly cause milder, medically responsive congenital hyperinsulinism. Rarer dominant mutations in these genes have been described that mostly cause milder, medically responsive congenital hyperinsulinism. To date the phenotype of patients with dominant mutations seems to be different from those with recessive mutations as the majority of patients are responsive to diazoxide therapy. Controversy exists on whether these dominant ABCC8 or KCNJ11 genes mutations predispose to diabetes mellitus in adulthood or not. Subjects: We report the clinical and genetic characteristics of five patients with neonatal HH, three had recessively inherited KATP channel mutations and two with a dominantly acting mutation. As a result of failure to medical therapy, patients with recessive KATP channel mutations underwent a near total pancreatectomy. Two siblings with a novel dominant mutation showed good response to medical treatment. Although the HH remitted in early infancy, they became diabetic at the prepubertal age. Their mother, maternal aunt and maternal grandfather had the same mutation without any medical history of neonatal HH. Conclusion: The clinical presentation of our two patients with a dominant ABCC8 mutation was milder than that of patients with the resessive form of the disease as they responded well to medical management.

Recurrent Streptococcus pneumoniae meningitis in a child with traumatic anterior cranial base defect.

Acute bacterial meningitis is a potentially life‐threatening infection of the cranial and spinal leptomeninges. Recurrent episodes of meningitis are rarely seen, but when they occur, an extensive investigation has to be made to find out responsible factors. 1–3 A single episode of acute meningitis may result from bacteriemia, but when followed by recurrent meningitis in pediatric patients, other possible routes of the bacteria invasion to the cerebrospinal fluid (CSF) should be considered. 1

Transient neonatal diabetes with two novel mutations in the KCNJ11 gene and response to sulfonylurea treatment in a preterm infant.

Abstract Neonatal diabetes mellitus (NDM) is a rare condition that can be either transient or permanent. KATP channel (Kir6.2 or SUR1) mutation, chromosome 6 abnormalities, insulin, or glucokinase gene mutations can lead to isolated NDM. Cases caused by Kir6.2 mutation usually result in permanent NDM (PNDM) rather than transient NDM (TNDM). The majority of patients with the Kir6.2 or SUR1 mutation can be successfully managed with a sulfonylurea agent, without the need for insulin. We report a preterm male with NDM having two novel missense mutations, E322A and D352H, in the KCNJ11 gene. At 2 months of age, successful transition from insulin to glibenclamide (glyburide) therapy of the patient was managed. At 5 months of age, his diabetes went in to remission.

Evaluation of hypercoagulability in obese children with thrombin generation test and microparticle release: effect of metabolic parameters.

Obesity is associated with a hypercoagulable state. Thrombin generation test (TGT) and microparticle levels were not studied in obese children extensively. It is aimed to determine whether any differences in the coagulation system between obese and normal weighed children exist with the use of TGT and microparticles release. A total of 120 obese and 38 healthy children were included to the study. An increase of thrombin generation and microparticles levels were found in obese children. Hyperinsulinism could not find a risk factor for hypercoagulability in our obese children. None of the parameters of TGT has been shown to be related to metabolic parameters and metabolic syndrome. Microparticles release time is found to correlate only to body mass index (BMI) Standard deviation score (SDS) in obese children. Hypercoagulability is associated with childhood obesity. Significant correlation between degree of obesity and microparticles release suggested that high adipokine levels secreted from adipose tissue can stimulate procoagulant status-independent metabolic dearrangements.

Contribution of clinical, metabolic, and genetic factors on hypertension in obese children and adolescents

Abstract The role of ACE gene insertion (I) or deletion (D) polymorphism on blood pressure phenotype is not clear in children. The aim of this work is to examine the association between hypertension and ACE I/D polymorphism, as well as the contribution of clinical and metabolic parameters on blood pressure. The study participants were 199 obese children. Forty-four of them were hypertensive. The hypertensive subjects were older than the normotensive and most of them were pubertal. The prevalence of hypertension in obese subjects with II, ID, and DD genotype was similar. There was no difference between the hypertensive and the normotensive group according to ACE I/D genotype, BMISDS, sex, blood glucose level and total cholesterol levels. In obese children, high IR-HOMA values, puberty, presence of family history for hypertension, hypertriglyceridemia, and low HDLcholesterol, high triglyceride/HDL-cholesterol ratio were found as increased risk factors of hypertension. In obese children and adolescents, blood pressure did not differ by ACE I/D genotype. The presence of family history, puberty, insulin resistance and hypertriglyceridemia constitute important risk factors for developing hypertension.

Clinical Review of 95 Patients with 46,XX Disorders of Sex Development Based on the New Chicago Classification

STUDY OBJECTIVE The aim of our study was to determine the etiologic distribution of 46,XX disorder of sexual development (DSD) according to the new DSD classification system and to evaluate the clinical features of this DSD subgroup in our patient cohort. PARTICIPANTS The evaluation criteria and clinical findings of 95 46,XX patients were described by clinical presentation, gonadal morphology, genital anatomy, associated dysmorphic features, presence during prenatal period with/without postnatal virilization, hormonal characteristics, and presence or absence of steroidogenic defects among 319 patients with DSD. RESULTS Types and ratios of each presentation of our 95 patients with 46,XX DSD were as follows: 82 had androgen excess (86.3%): (74 had classical congenital adrenal hyperplasia, 2 had CAH variant possibility of P450-oxidoreductase gene defect), 6 had disorders of ovarian development (6.3%): (1 patient had gonadal dysgenesis with virilization at birth with bilateral streak gonad, 4 patients had complete gonadal dysgenesis, and 1 patient had ovotesticular DSD) and 7 had other 46,XX DSD. Two sisters, who had 46,XX complete gonadal dysgenesis,were diagnosed with Perrault Syndrome with ovarian failure due to streak gonads and associated with sensorineural deafness. CONCLUSION 46,XX DSD are usually derived from intrauterine virilization and CAH is the most common cause of 46,XX DSD due to fetal androgen exposure.