Eileen C.P. Lim

A118G single nucleotide polymorphism of human μ-opioid receptor gene influences pain perception and patient-controlled intravenous morphine consumption after intrathecal morphine for postcesarean analgesia

Background:Previous studies have shown that genetic variability at position 118 of the human &mgr;-opioid receptor gene altered patients’ response to intravenous morphine. The purpose of this study was to investigate whether this polymorphism contributes to the variability in response to morphine for postcesarean analgesia. Methods:After investigators obtained informed consent, 588 healthy women received 0.1 mg intrathecal morphine for postcesarean analgesia. Their blood samples were genotyped for the A118G polymorphism—A118 homozygous (AA), heterozygous (AG), or homozygous for the G allele (GG). Pain scores, the severity of nausea and vomiting, the incidence of pruritus, and the total self-administered intravenous morphine were recorded for the first 24 postoperative hours. Results:Two hundred seventy women (46%) were AA, 234 (40%) were AG, and 82 (14%) were GG. The 24-h self-administered intravenous morphine consumption was lowest in the AA group (P = 0.001; mean, 5.9; 95% confidence interval, 5.1–6.8) versus the AG (8.0; 6.9–9.1) and GG groups (9.4; 7.3–11.5). Pain scores were lowest in the AA group and highest in the GG group, with a statistically significant difference detected between AA, AG, and GG (P = 0.049). Total morphine consumption was also influenced by patients’ age and paying status. AA group was associated with the highest incidence of nausea (26 of 272 [9.6%]; P = 0.02) versus the other two groups (13 of 234 [5.6%] and 1 of 82 [1.2%] for AG and GG, respectively). Conclusion:Genetic variation at position 118 of the &mgr;-opioid receptor is associated with interindividual differences in pain scores, self-administered intravenous morphine, and the incidence of nausea postoperatively.

Influence of Mu-Opioid Receptor Variant on Morphine Use and Self-Rated Pain Following Abdominal Hysterectomy

UNLABELLED A common variant in the mu-opioid receptor gene (OPRM1) has been associated with response to opioid analgesia. Our previous data revealed significantly higher amounts of morphine self-administered by patients carrying the 118G allele compared to those with the 118A allele after elective cesarean section. In this study, the association of this genetic variation with pressure pain, postoperative pain scores, and amount of morphine used was investigated in 973 patients undergoing scheduled total hysterectomy under general anesthesia. Preoperative pressure pain threshold and tolerance were also measured for most patients. For pressure pain, OPRM1 genotype was not significantly associated with either pain threshold or pain tolerance. Statistically significant associations were found for postoperative pain and the total amount of morphine used, with the GG group reporting higher pain scores and using the most morphine. When analysis was stratified by ethnic group, differences in weight-adjusted morphine for the 3 genotypic groups were also significant for the Chinese and Asian Indians. These results extend our previous finding on the association of higher self-reported pain and morphine use for acute postoperative pain with OPRM1 118G to patients who had total hysterectomy under general anesthesia. PERSPECTIVE In a large cohort of patients undergoing hysterectomy, we found large variability in the self-rated pain scores and the amount of morphine required for pain relief. Both are associated with OPRM1 genotypes and preoperative experimental pressure pain threshold. Experimental pressure pain tolerance is also associated with postoperative pain.

An Additional Case of the Recurrent 15q24.1 Microdeletion Syndrome and Review of the Literature

We report a 9-year-old girl with 3 Mb interstitial deletion of chromosome 15q24 identified by oligonucleotide array comparative hybridization. She is of Chinese ancestry and shared some typical features of previously reported 15q24 deletion cases such as mild dysmorphism with developmental and speech delay. She also had mild hearing loss that was reported in one other case. We compared all 19 cases that are identified from array-CGH. The deletion occurred within an 8.3 Mb region from 15q23 to 15q24.3. The minimum overlapping deleted region is less than 0.5 Mb from 72.3 Mb to 72.7 Mb. The functions of the nine annotated genes within the region and how they might contribute to the microdeletion phenotype are discussed.

A submicroscopic deletion involving part of the CREBBP gene detected by array-CGH in a patient with Rubinstein-Taybi syndrome

We report a girl with Rubinstein-Taybi syndrome (RSTS) who was found to have copy number loss on 16p13.3 by array-CGH. She has developmental delay and other features of RSTS including downslanting palpebral fissures, a prominent nose with the nasal septum extending below the alae nasi, broad thumbs and big toes, postaxial polydactyly of the right foot and constipation from birth. We report the junction sequence across the breakpoint region for a microdeletion in RSTS. The sequencing results also showed that the deletion was 81.4kb involving three genes DNASE 1, TRAP 1, and CREBBP.

De novo 3q22.1 q24 deletion associated with multiple congenital anomalies, growth retardation and intellectual disability.

We describe a boy with a de novo deletion of 15.67 Mb spanning 3q22.1q24. He has bilateral micropthalmia, ptosis, cleft palate, global developmental delay and brain, skeletal and cardiac abnormalities. In addition, he has bilateral inguinal hernia and his right kidney is absent. We compare his phenotype with seven other patients with overlapping and molecularly defined interstitial 3q deletions. This patient has some phenotypic features that are not shared by the other patients. More cases with smaller deletions defined by high resolution aCGH will enable better genotype-phenotype correlations and prioritizing of candidate genes for the identification of pathways and disease mechanisms.

Cockayne Syndrome due to a maternally-inherited whole gene deletion of ERCC8 and a paternally-inherited ERCC8 exon 4 deletion.

Cockayne Syndrome (CS) is an autosomal recessive disorder that causes neurological regression, growth failure and dysmorphic features. We describe a Chinese female child with CS caused by deletions of exon 4 of ERCC8 on one chromosome and exons 1-12 on the other chromosome. By using chromosomal microarray, multiplex ligation-dependant probe analysis and long range PCR, we showed that she inherited a 277 kb deletion affecting the whole ERCC8 gene from the mother and a complex rearrangement resulting in deletion of exon 4 together with a 1,656 bp inversion of intron 4 from the father. A similar complex rearrangement has been reported in four unrelated Japanese CS patients. Analysis of the deletion involving exon 4 identified LINE and other repeat elements that may predispose the region to deletions, insertions and inversions. The patient also had insulin-dependent diabetes mellitus, a rare co-existing feature in patients with CS. More research will be needed to further understand the endocrine manifestations in CS patients.

Intragenic multi-exon deletion in the FBN1 gene in a child with mildly dilated aortic sinus: a retrotransposal event

Marfan syndrome is an autosomal dominant disorder affecting mainly the skeletal, ocular and cardiovascular systems. Most cases are caused by mutations in the fibrillin-1 gene (FBN1), although there are some reports on deletions involving FBN1 and other additional genes. We report a male patient who was first evaluated at 4 years of age. Echocardiogram showed a mildly dilated aortic sinus. He also had a history of muscular ventral septal defect which was closed spontaneously and trivial mitral regurgitation. Other phenotypic features include frontal bossing, anteverted ears, joint hyperlaxity, learning disability, skin striae, and height and weight in the >97th centile but no other diagnostic findings of MFS and does not fulfill the revised Ghent criteria. Chromosomal microarray analysis showed a deletion of approximately 36.8 kb at 15q21.1, which starts in intron 6 and ends in intron 9 and includes three FBN1 exons. Sequence analysis of the breakpoint region confirmed the deletion and revealed a concomitant insertion of a retrotransposon within the intron 6/intron 9 region. The intragenic deletion of exons 7–9 was likely the result of a retrotransposition event by a MAST2-SVA element mediated by repetitive sequences.

Piebaldism with multiple café-au-lait–like hyperpigmented macules and inguinal freckling caused by a novel KIT mutation

CALM: caf e-au-lait macules NF1: neurofibromatosis type 1 TK: tyrosine kinase INTRODUCTION Piebaldism is a rare autosomal dominant disorder of pigmentation characterised by patches of leukoderma and white forelock. It is most often caused by mutations in the KIT proto-oncogene receptor tyrosine kinase (TK), which result in the defective migration and differentiation of melanoblasts and melanocytes. Other mutations that have been described include a deletion and a double nucleotide variant in the gene encoding snail family zinc finger 2 (SNAI2/SLUG). The occasional coexistence of multiple caf e-aulait macules (CALMs) in piebaldism and also piebaldism in association with CALMs and intertriginous freckling may lead to diagnostic confusion with neurofibromatosis type 1 (NF1). Another differential diagnosis is Legius syndrome, which is caused by loss-of-function mutations in the SPRED1 gene. The syndrome is characterised by CALMs and intertriginous freckling with macrocephaly, lipomas, and learning disability. Unlike NF1, patients with Legius syndrome do not have cutaneous or plexiform neurofibromas, skeletal dysostosis, or optic pathway gliomas. The overlapping presentations of these related pigmentary disorders make it difficult to distinguish between them during the early stages and present a challenge for initial diagnosis.

A Novel Interferon Regulatory Factor 6 Mutation in an Asian Family With Van der Woude Syndrome.

Van der Woude syndrome (VWS) is a rare autosomal dominant genetic disorder characterized by orofacial clefting and lip pits. Mutations in the transcription factor interferon regulatory factor 6 gene (IRF6) have been identified in individuals with VWS. We performed direct sequencing of the gene for molecular investigation of a proband with Bangladeshi-Malay ancestry. A novel transition mutation (c.113T>C), which resulted in an amino acid substitution (p.Ile38Thr) in the deoxyribonucleic acid-binding domain was detected. Testing of family members showed that the mutation segregated with the VWS phenotype for members of her immediate family. Although there is some phenotypic variability, all of the affected members are of the female gender.

Cytogenomic Delineation and Clinical Characterization of Three Cases of MECP2 Duplication Syndrome

The methyl-CpG-binding protein 2 gene (MECP2) on the X chromosome encodes an essential epigenetic regulator in human postnatal brain development. Increased dosage of MECP2 causes a severe syndromic form of intellectual disability, the MECP2 duplication syndrome. Males with this syndrome have a progressive neurological disorder, severe to profound intellectual disability, epilepsy and recurrent respiratory infections. We report three cases with copy number gain in Xq28 involving the MECP2 gene. The gains were detected by chromosomal microarray analysis and ranged in size from 300 kb to 4.96 Mb. The three boys were aged between 3 and 16 years old. All three had development delay and no speech. In addition, one patient was diagnosed with Lennox-Gastaut syndrome and another had a Dandy Walker variant. Their clinical features were compared with other reported cases. We concluded that all three patients’ clinical features were due to the Xq28 duplication, which confirmed the utility of chromosomal microarray analysis as a first-tier test in patients with unexplained intellectual disability. With a specific genetic diagnosis, we were able to provide appropriate anticipatory guidance for these patients and their families.