Next generation sequencing of RB1gene for the molecular diagnosis of ethnic minority with retinoblastoma in Yunnan.

BACKGROUND: Retinoblastoma is a rare intraocular malignancy and typically initiated by inactivating biallelic mutations of RB1 gene. Each year, ~ 8000 children worldwide are diagnosed for retinoblastoma. In high-income countries, patient survival is over 95% while low-income countries is ~ 30%.If disease is diagnosed early and treated in centers specializing in retinoblastoma, the survival might exceed 95% and many eyes could be safely treated and support a lifetime of good vision. In China, approximate 1100 newly diagnosed cases are expected annually and 28 hospitals covering 25 provinces established centers classified by expertise and resources for better treatment options and follow-up. Comparing with other province of eastern China, Yunnan province is remote geographically. This might result that healthcare staff have low awareness of the role of genetic testing in management and screening in families. METHODS: The patients with retinoblastoma were selected in Yunnan. DNA from blood was used for targeted gene sequencing. Then, an in-house bioinformatics pipeline was done to detect both single nucleotide variants and small insertions/deletions. The pathogenic mutations were identified and further confirmed by conventional methods and cosegregation in families. RESULTS: Using our approach, targeted next generation sequencing was used to detect the mutation of these 12 probands. Bioinformatic predictions showed that nine mutations were found in our study and four were novel pathogenic variants in these nine mutations. CONCLUSIONS: It's the first report to describe RB1 mutations in Yunnan children with retinoblastoma. This study would improve role of genetic testing for management and family screening.

Racial, Ethnic, and Socioeconomic Disparities in Retinoblastoma Enucleation: A Population-Based Study, SEER 18 2000-2014.

PURPOSE: To determine the effect of race, ethnicity, and census tract-level composite socioeconomic status (SES) on retinoblastoma enucleation. This study augments Truong and associates, providing multivariate analyses combining sociodemographic and clinical characteristics with more accurate SES measures. We hypothesized that children from nonwhite, Hispanic, and lower socioeconomic backgrounds would have increased adjusted odds of enucleation. DESIGN: Retrospective cohort analysis. SETTING: Multicenter population-based study using the Surveillance, Epidemiology, and End Results (SEER) 18 Registries. STUDY POPULATION: Children aged 18 years and younger diagnosed with retinoblastoma between 2000 and 2014. Subjects were identified using International Classification of Diseases-Oncology (ICD-O) site and morphology codes. MAIN OUTCOME MEASURES: Enucleation odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Analysis of 959 retinoblastoma patients revealed that 70.8% were enucleated. Adjusted analyses showed associations between enucleation and Asian (OR 2.00, CI 1.08-3.71) or black (2.42, 1.41-4.16) race, Hispanic ethnicity (1.69, 1.16-2.46), and low SES (1.68, 1.09-2.58). Significantly increased enucleation risk was associated with older age at diagnosis (age 1-2 years 2.55, 1.80-3.61; >2 years 4.88, 2.57-9.25), unilateral disease (5.00, 3.45-7.14), and advanced stage (regional 4.71, 2.51-8.84; distant 3.15, 1.63-6.08). No interactions were observed between race, ethnicity, SES, and stage at diagnosis. Enucleation rates decreased over time across all racial, ethnic, and socioeconomic groups. CONCLUSIONS: Children from nonwhite, Hispanic, and lower socioeconomic backgrounds are more likely to receive enucleation. These associations are independent of stage of diagnosis, suggesting larger systemic disparities in retinoblastoma care. The origin of these differences requires further study and attention by clinicians and policy makers.

Spectrum of mutations in the RB1 gene in Vietnamese patients with retinoblastoma.

Purpose: Retinoblastoma (RB) is a rare childhood malignant disorder caused by the biallelic inactivation of the RB1 gene. Early diagnosis and identification of carriers of heritable mutations in RB1 can improve disease outcome and management. In this study, we present the spectrum of mutations in the RB1 gene in Vietnamese patients with RB. Methods: Tumor RNA from 50 probands with RB, including 12 bilateral and 38 unilateral cases, was extracted. cDNA, after reverse transcription, was sequenced to identify the RNA mutation of the RB1 gene. At the genomic DNA level, mutational analysis of all RB1 exons, exon-intron boundaries, and the promoter region was conducted using PCR and direct sequencing. Multiplex ligation-dependent probe amplification (MLPA) analysis was performed for patients for whom the first two results were negative. For patients for whom either the sequencing or MLPA results were positive for a tumor mutation, patients' and their parents' blood DNA was analyzed to determine the germline mutation. Results: Forty-one different kinds of RB1 tumor mutations were identified in 41 probands (82.0%), including 11 of 12 bilateral cases (91.7%) and 30 of 38 unilateral cases (78.9%). The majority of the detected mutations were nonsense (15 different kinds), followed by frameshift (11 kinds), and splice site mutations (nine kinds). Each splice site mutation was confirmed to create a deletion of the corresponding exon with RNA sequencing. The single promoter mutation c.-197G>A was reported previously; however, both missense mutations identified in exon 6 (c.601G>C: p.A201P) and exon 22 (c.2264T>C: p.F755S) were novel. Gross deletions were detected with MLPA in three probands. The detection rate of germline mutations in bilateral and unilateral cases with mutations were 81.8% and 30.0%, respectively. Only one father out of the 20 parents tested was positive for a germline mutation. Conclusions: Mutations in the RB1 gene in Vietnamese patients were heterogeneous and highly prevalent with pathogenic truncated mutations. With advancement in therapeutics, early detection of RB is important for eye salvation.

Mutational screening of germline RB1 gene in Vietnamese patients with retinoblastoma reveals three novel mutations.

Purpose: Retinoblastoma (Rb) is a rare and unique eye cancer that usually develops in the retinas of children less than 5 years old due to mutations in the RB1 gene. About 40% of affected individuals have the heritable form making genetics testing of the RB1 gene important for disease management. This study aims to identify germline mutations in RB1 in a cohort of patients with Rb from northern Vietnam. Methods: Genomic DNA was extracted from peripheral blood of 34 patients with Rb (nine unilateral and 25 bilateral cases) and their available parents. Twenty-seven exons, flanking sequences, and the promoter region of RB1 gene were screened for mutations with direct PCR sequencing. Multiplex ligation-dependent probe amplification (MLPA) was applied for patients with negative sequencing results. In the mutation-positive patients, their available parental DNA was analyzed to determine the parental origin of the mutation. Results: Germline mutations in RB1 were identified in 25 (73.53%) of 34 patients (four unilateral and 21 bilateral cases). Of these mutations, 19 were detected, including seven nonsense, six frameshift, four splice-site (one was identified in two siblings), and one missense, with Sanger sequencing. Three novel frameshift mutations were discovered in one unilateral and two bilateral patients. MLPA detected mutations in the RB1 gene in six bilateral cases, of whom five had a whole gene deletion (three familial cases) and one had a partial gene deletion (from exon 4 to exon 27) in one allele of the RB1 gene. Parental testing showed five mutations originated from the fathers and one was inherited from a mother who was mosaic for the mutation. Conclusions: This study provides a data set of germline mutations in the RB1 gene in Vietnamese patients with retinoblastoma. Screening of mutations in the RB1 gene can help to identify heritable Rb and contribute to clinical management and genetic counseling for affected families.

Clinical Presentation and Outcomes of Stage III or Stage IV Retinoblastoma in 80 Asian Indian Patients.

PURPOSE: To describe the clinical features and outcomes of patients with stage III or IV retinoblastoma. METHODS: This was a retrospective study of 80 patients. RESULTS: Based on the International Retinoblastoma Staging System (IRSS), the tumors (n = 81) belonged to stage IIIa (n = 38, 47%), IIIb (n = 1, 1%), IVa2 (n = 10, 12%), IVb1 (n = 14, 17%), and IVb3 (n = 18, 22%). Of 80 patients, 42 (53%) were compliant to treatment and 38 (47%) were non-compliant. All 38 patients who were non-compliant to treatment died of the disease at a mean duration of 13 months from diagnosis. Of the 42 patients compliant to treatment, 22 (52%) died before completion of treatment. Twenty patients with stage III disease (25%) could complete the multimodal treatment and 17 (71%) were alive and well at a median follow-up duration of 77 months. CONCLUSIONS: Compliant multimodality treatment is beneficial in patients with IRSS stage III disease. IRSS stage IV retinoblastoma has poor prognosis despite treatment. [J Pediatr Ophthalmol Strabismus. 2017;54(3):177-184.].

A Functional Polymorphism (rs937283) in the MDM2 Promoter Region is Associated with Poor Prognosis of Retinoblastoma in Chinese Han Population.

The effect of single nucleotide polymorphisms (SNPs) at MDM2 has been investigated in several cancer types. Three MDM2 SNPs(rs937283, rs2270744 and rs769412) have previously been suggested to be positively correlated with cancer. In this study, we aimed to explore the association of rs937283, rs2270744 and rs769412 polymorphisms with retinoblastoma (RB) risk, clinicopathological characteristics, and prognosis. Compared with wild-type genotype AA at rs937283, individuals carrying AG and GG genotype had a significantly increased risk for developing RB (OR = 1.86, 95% CI 1.13-3.08; OR = 2.48, 95% CI 1.10-5.62, respectively). RB patients with allele G at rs937283 were more susceptible to invasion and high tumor aggression (OR = 2.42, 95% CI 1.43-4.11; OR = 2.15, 95% CI 1.27-3.64, respectively). Kaplan-Meier curves and log-rank results revealed that RB patients harboring genotype GG and G allele at rs937283 had worse survival (P < 0.02 and P < 0.01, respectively). In addition, the A to G substitution at rs937283 significantly enhanced the transcription activity of the MDM2 gene in vitro. In vivo, we found that MDM2 mRNA and protein were overexpressed in individuals who carried the G allele at rs937283. This study suggested that the MDM2 rs937283 polymorphism is a novel functional SNP both in vitro and in vivo as well as a biomarker for poor prognosis in RB.

Spectrum of germ-line RB1 gene mutations in Malaysian patients with retinoblastoma.

PURPOSE: The availability of molecular genetic testing for retinoblastoma (RB) in Malaysia has enabled patients with a heritable predisposition to the disease to be identified, which thus improves the clinical management of these patients and their families. In this paper, we presented our strategy for performing molecular genetic testing of the RB1 gene and the findings from our first 2 years of starting this service. METHODS: The peripheral blood of 19 RB probands, including seven bilateral and 12 unilateral cases, was obtained, and genomic DNA was extracted. Analysis of the RB1 exons and the promoter region was conducted first using PCR and direct sequencing. Next, multiplex ligation-dependent probe amplification (MLPA) analysis was performed for patients whom the first results were negative. For patients whom either the first or second method results were positive, parental samples were analyzed to determine the origin of the mutation. RESULTS: Ten RB1 mutations were identified in ten (52.6%) of the 19 probands (seven bilateral and three unilateral cases), of which 30.0% (3/10) was identified with MLPA. The detection rates in the bilateral and unilateral cases were 100.0% (7/7) and 25.0% (3/12), respectively. Three new RB1 mutations were discovered, two in patients with bilateral RB and one in patient with unilateral RB. Interestingly, all mutations detected with the PCR-sequencing method were predicted to create a premature stop codon. Eight mutations were proven to be de novo while one mutation was inherited from the mother in a family with a positive history of RB. CONCLUSIONS: Our results confirmed the heterogeneous nature of RB1 mutations and the predominantly de novo origin. The high prevalence of pathogenic truncating mutations was evident among local patients with RB. The combination of PCR sequencing and MLPA is recommended for sensitive identification of heritable RB cases.

Ethnic, Racial, and Socioeconomic Disparities in Retinoblastoma.

IMPORTANCE: Most children with retinoblastoma in the United States are diagnosed as having a large intraocular tumor burden that requires intensive ocular-salvage treatment or enucleation. OBJECTIVE: To investigate the effect of socioeconomic status, race, and ethnicity on the extent of disease and the outcomes of retinoblastoma. DESIGN, SETTING, AND PARTICIPANTS: A population-based review of 18 Surveillance, Epidemiology, and End Results (SEER) registries. From January 1, 2000, through December 31, 2010, 830 cases of retinoblastoma were recorded for children aged 0 to 9 years. Data were collected and analyzed from January 1, 2000, through December 31, 2010, with the last follow-up on December 31, 2010. EXPOSURES: County-based socioeconomic variables analyzed included poverty level, educational attainment, language isolation, crowding, unemployment, and percentage of immigrants. MAIN OUTCOMES AND MEASURES: Extent of disease, ocular outcome, and children's survival. RESULTS: Of the 830 individuals included, Hispanic children had a higher percentage of extraocular disease (86 of 261 [33.0%] vs. 102 of 510 non-Hispanic children [20.0%]; odds ratio [OR], 1.97 [95% CI, 1.38-2.79]). The percentage of extraocular cases was also higher in counties with the following low socioeconomic status indicators: higher vs. lower poverty status (115 of 413 [27.8%] vs. 73 of 358 [20.4%]; OR, 1.51; 95% CI, 1.06-2.14); lower vs. higher educational attainment (115 of 400 [28.7%] vs. 73 of 371 [19.7%]; OR, 1.65; 95% CI, 1.16-2.34); higher vs. lower levels of crowding (124 of 398 [31.2%] vs. 64 of 373 [17.2%]; OR, 2.18; 95% CI, 1.53-3.13); higher vs. lower unemployment (119 of 411 [28.9%] vs. 69 of 360 [19.2%]; OR, 1.72; 95% CI, 1.21-2.45); higher vs. lower language isolation (117 of 388 [30.2%] vs. 71 of 383 [18.5%]; OR, 1.89; 95% CI, 1.34-2.70); and higher vs. lower percentage of immigrants (109 of 386 [28.2%] vs. 79 of 385 [20.5%]; OR, 1.52; 95% CI, 1.08-2.16). Higher rates of enucleation were associated with low educational attainment (265 of 401 [66.1%] vs 309 of 421 [73.4%]; OR, 1.42; 95% CI, 1.04-1.93), a higher level of crowding (316 of 416 [76.0%] vs. 258 of 406 [63.5%]; OR, 1.81; 95% CI, 1.32-2.48), and Hispanic origin (202 of 271 [74.5%]; OR, 1.41; 95% CI, 1.01-1.98). Relative survival at 5 years was lower among black compared with non-Hispanic white children (92.7% vs. 99.2%; P < .001). CONCLUSIONS AND RELEVANCE: Significant disparities exist in the care and outcomes of children with retinoblastoma. A low socioeconomic status negatively affects disease extent and ocular outcomes, presumably by limiting access to primary and cancer-directed care. Hispanic children in particular have more advanced disease and higher rates of enucleation.

Alterations in the RB1 gene in Pakistani patients with retinoblastoma using direct sequencing analysis.

PURPOSE: Retinoblastoma (RB) is a rare intraocular malignant tumor of the developing retina with an estimated incidence of 1:20,000 live births in children under the age of 5 years. In addition to the abnormal whitish appearance of the pupil or leukocoria, strabismus has also been reported as a clinical symptom of the disease. RB1 is the first cloned tumor suppressor gene, and mutational inactivation of this gene is responsible for the development of RB during early childhood. The purpose of this study was to identify mutational alterations in the RB1 gene in Pakistani patients with RB. METHODS: During this study, 70 clinically evaluated patients with RB were recruited from different regions of Pakistan. The cases included 23 sporadic bilateral (32.9%), 34 sporadic unilateral (48.6%), nine familial bilateral (12.8%), and four familial unilateral (5.7%) cases. Constitutional causative mutations in the RB1 gene were screened via direct sequencing of all RB1 exons and their flanking regions. RESULTS: In this report, genetic testing resulted in the identification of 18 mutations in 25 patients with RB including six novel RB1 mutations. Of the total mutations identified, 13 (72.22%) were found to be null mutations caused by nine nonsense, three deletions, and one insertion. Two (11.11%) missense, two (11.11%) splice site mutations, and one (5.55%) base substitution in the promoter region were also found. Moreover, ten intronic variants were identified, one of which is novel. CONCLUSIONS: Molecular screening and identification of these mutations in Pakistani patients with RB provide the mutational variants of the RB1 gene in the Pakistani population. The detection of oncogenic mutations in patients with RB and genetically predisposed individuals is a major step in clinical management, prognosis, follow-up care, accurate genetic counseling, and presymptomatic diagnosis of RB.

[Epidemiological and clinical characteristics of primary ocular cancers in blacks: our experience with 111 cases]. / Aspects épidémiologiques et cliniques des cancers oculaires primitifs du mélanoderme : notre expérience à propos de 111 cas.

INTRODUCTION: In this work, the authors aim to study clinical and epidemiological characteristics of ocular and orbital primary cancers in sub-Saharan African. PATIENTS AND METHODS: This is a retrospective study over a period of 21 years, from 1984 to 2004, including all cases of ocular cancer, histologically proven after surgery of the globe or the orbit. For each patient, we studied the following parameters: age, sex, reason(s) for consultation, the affected eye, and histological result of the operative specimen. These data were collected by studying the departmental surgical registry, patient medical records and the tumor registry of the anatomicopathology laboratory of a tertiary care hospital in sub-Saharan Africa. RESULTS: We collected data on 111 black patients, among whom 15 cases (13.5%) presented with bilateral involvement, for a total of 126 eyes. The sex ratio was 1.17. Presenting signs showed a predominance of leukocoria (30.2%) followed by proptosis (21.7%) and in third place, protruding conjunctival mass (10.8%). Retinoblastoma was found most frequently, representing 66.6% of the oculo-orbital tumors and 95.45% of the tumors of the globe; followed by epidermoid carcinoma, representing 15.08% of cases. Malignant melanoma was third most common, representing 4.76%, with 83% arising in the anterior uvea and 7% in the choroid. Basal cell carcinoma and rhabdomyosarcoma follow in fourth place. Basal cell carcinoma constituted half (50%) of the eyelid tumors. Rhabdomyosarcoma was the most common orbital tumor in our series (57%). Next were lymphomas with conjunctival localization (2.38%), acute leukemia with orbital localization (1.59%) and rare tumors, palpebral dermatofibrosarcoma (0.79%), an orbital angiosarcoma (0.79%), a glioblastoma of the globe (0.79%) and a malignant solitary fibrous tumor of the orbit (0.79%). CONCLUSION: Ocular and orbital primary cancers in blacks remain tumors of the young, equally distributed between the sexes. Retinoblastoma is the most frequent, followed by epidermoid carcinoma. The globe is the preferential localization of these cancers.

The modern role of radiation therapy in treating advanced-stage retinoblastoma: long-term outcomes and racial differences.

PURPOSE/OBJECTIVE(S): To evaluate the effects of various patient characteristics and radiation therapy treatment variables on outcomes in advanced-stage retinoblastoma. METHODS AND MATERIALS: This was a retrospective review of 41 eyes of 30 patients treated with external beam radiation therapy between June 1, 1992, and March 31, 2012, with a median follow-up time of 133 months (11 years). Outcome measures included overall survival, progression-free survival, local control, eye preservation rate, and toxicity. RESULTS: Over 90% of the eyes were stage V. Definitive external beam radiation therapy (EBRT) was delivered in 43.9% of eyes, adjuvant EBRT in 22% of eyes, and second-line/salvage EBRT in 34.1% of eyes. A relative lens sparing (RLS) technique was used in 68.3% of eyes and modified lens sparing (MLS) in 24.4% of eyes. Three eyes were treated with other techniques. Doses ≥45 Gy were used in 68.3% of eyes. Chemotherapy was a component of treatment in 53.7% of eyes. The 10-year overall survival was 87.7%, progression-free survival was 80.5%, and local control was 87.8%. White patients had significantly better overall survival than did African-American patients in univariate analysis (hazard ratio 0.09; 95% confidence interval 0.01-0.84; P=.035). Toxicity was seen in 68.3% of eyes, including 24.3% with isolated acute dermatitis. CONCLUSIONS: External beam radiation therapy continues to be an effective treatment modality for advanced retinoblastoma, achieving excellent long-term local control and survival with low rates of treatment-related toxicity and secondary malignancy.

Perinatal characteristics and retinoblastoma.

PURPOSE: The etiology of retinoblastoma remains poorly understood. In the present study, we examined associations between perinatal factors and retinoblastoma risk in California children. METHODS: We identified 609 retinoblastoma cases (420 unilateral, 187 bilateral, and 2 with laterality unknown) from California Cancer Registry records of diagnoses 1988-2007 among children < 6 years of age. We randomly selected 209,051 controls from California birth rolls. The source of most study data was birth certificates. Multivariable logistic regression was used to examine associations between retinoblastoma and perinatal characteristics. RESULTS: Bilateral retinoblastoma was associated with greater paternal age [for fathers over 35, crude odds ratio (OR) = 1.73, 95 % confidence interval (CI) 1.20, 2.47] and with twin births (OR = 1.93, 95 % CI 0.99, 3.79). Among unilateral cases, we observed an increased risk among children of US-born Hispanic mothers (OR = 1.34, 95 % CI 1.01, 1.77) while a decreased risk was observed for infants born to mothers with less than 9 years of education (OR = 0.70, 95 % CI 0.49, 1.00), a group that consisted primarily of mothers born in Mexico. We observed that maternal infection in pregnancy with any STD (OR = 3.59, 95 % CI 1.58, 8.15) was associated with bilateral retinoblastoma. CONCLUSIONS: This study supports the findings of previous investigations reporting associations between parental age, HPV infection, and retinoblastoma.

The effect of race on the incidence of retinoblastoma.

PURPOSE: To examine the incidence of retinoblastoma for regional variations by race. METHODS: Age-adjusted incidence rates, rate ratios, and 95% confidence intervals were determined in 109 regions from 1993 to 1997 using compiled data from the International Agency for Research on Cancer. RESULTS: The rate ratio was 1.12 (range: 0.35 to 4.15) between white populations in the United States and Europe/Australia, 0.98 (range: 0.37 to 2.65) between Hispanic populations in Spain and the United States, and 1.44 (range: 0.29 to 1.79) between Hispanic populations in Uruguay and the United States. The rate ratio between Hispanic and white populations within the United States was 0.94 (range: 0.33 to 2.56). No differences were significant. CONCLUSIONS: Because retinoblastoma is a genetic disease, its incidence is similar among varied populations.

The clinical spectrum and treatment outcome of retinoblastoma in Indian children.

PURPOSE: To study the clinical spectrum and treatment outcome of retinoblastoma in Indian children. PATIENTS AND METHODS: This retrospective study analyzed 488 eyes of 355 retinoblastoma patients treated at a tertiary care ophthalmic hospital in southern India during a 14-year period. RESULTS: Retinoblastoma involved one eye in 177 (50%) and both eyes in 178 (50%) patients. Mean age at presentation was 23.98 +/- 23.37.

Ethnic variations of a retinoblastoma susceptibility gene (RB1) polymorphism in eight Asian populations.

An A --> G single nucleotide polymorphism (SNP) at nucleotide 153,104 in the retinoblastoma susceptibility locus (RB1) at 13q14 was previously reported to be present only in Asians. In this study, we determined the distribution of this SNP in normal Southeast Asian populations (Chinese, Malay, Javanese, Thai, Filipino), in South Asian populations (Bangladeshi, Pakistani Pushtun and Indian) and in Chinese retinoblastoma cases and control subjects. The RB1 SNP was present in all populations at an overall frequency of =/< 0.18. Heterozygosity was higher in the Southeast Asian groups (0.14-0.34) than in the South Asian groups (Bangladeshi and Indian) (0.04-0.06). Significant differences in allele frequencies were found between the two population groups. Interestingly, our Pakistani population comprised of ethnic Pushtuns from northwest Pakistan was significantly different from the neighbouring Bangladeshi and Indian populations. No significant difference was found between Chinese case patients and control subjects. This RB1 SNP appears to be an ethnic variant prevalent in Southeast Asian populations and may be useful for studying RB1 inheritance by pedigree analysis.

Molecular-genetic analysis of two cases with retinoblastoma: benefits for disease management.

Effective counselling and management of retinoblastoma families using genetic information is presently practised in many parts of the world. We studied histopathological, chromosomal and molecular-genetic data of two retinoblastoma patients from India. The two patients, one with bilateral and the other with unilateral retinoblastoma, underwent complete ophthalmic examination, cytogenetic study, retinoblastoma gene (RB1) mutational analysis and RB1 promoter region methylation screening. In the bilateral retinoblastoma patient deletion of chromosome region 13q14 in peripheral blood lymphocytes and a hemizygous novel 8-bp deletion in exon 4 of RB1 in tumour sample were observed. In the unilaterally affected patient CGA to TGA transition protein truncation mutations were observed in exons 8 and 14 of RB1.

Mutational analysis of the RB1 gene in Indian patients with retinoblastoma.

Twenty-one probands, twelve with bilateral and nine with unilateral retinoblastoma, were screened for mutations in the RB1 gene using genomic DNA from peripheral blood leukocytes as well as tumors. Amplification of individual exons and flanking regions of the RB1 gene were carried out, followed by direct sequencing of the amplified products. Sequences of affected individuals were compared with those of controls. Mutations were identified in seven patients, five with bilateral and two with unilateral retinoblastoma. Six out of seven mutations involved the formation of premature termination codons by means of single base substitutions (2), frameshifts due to splice-site mutations (2), or deletion and duplication (2). One missense mutation was identified. Of the remaining fourteen patients, seven with bilateral disease had no mutations in peripheral blood (7 cases) or tumors (3/7 cases). Analysis of the peripheral blood of seven patients with unilateral disease also showed no mutations. Mutations were detected in about one-third of the cases, suggesting that hemizygous deletions at the RB1 locus or mutations outside the coding regions of RB1 may be responsible for the disease in the remaining patients.

Detection of mutations in argentine retinoblastoma patients by segregation of polymorphisms, exon analysis and cytogenetic test.

The aim of this study was to detect chromosomal and molecular abnormalities in 16 Argentine families with retinoblastoma (RB). Chromosomes were analyzed by G-banding, DNA from leukocytes and tumors was studied by segregation of polymorphisms within RB gene (RB1) and the DNA from chorionic villus by sequencing. The karyotype of an Rb236 bilateral patient with dismorphic signs revealed a deletion in 13q13-21. Polymorphism and exon analyses showed a deletion in the 3' end of RB1 in an Rb72 patient. The mutant RB1 allele, detected by loss of heterozygosity (LOH) in the tumor, was identified in 14 out of 18 tumors. The analysis of chorionic villus revealed a mutation, a C-to-T transition in exon 18. Molecular and cytogenetic analyses in families with RB offer valuable information on how to assess the risk of tumor development.

Further delineation of the facial 13q14 deletion syndrome in 13 retinoblastoma patients.

Thirteen years ago, Motegi and colleagues (J Med Genet 1987;24:696-697) summarized the specific facial phenotype of six Japanese retinoblastoma patients with interstitial 13q14 deletions. Among a series of 228 propositi with retinoblastoma referred to the Lausanne Retinoblastoma Clinic for treatment and genetic counseling between 1986 and 1997, 13 (5.7%) were diagnosed with a cytogenetic de-novo 13q14 deletion. We confirm the presence of the reported facial phenotype in our population of Caucasian patients and describe additional clinical traits, thus extending the facial phenotype associated with the 13q14 deletion. Del(13q14) comprises, among others, cranial anomalies, frontal bossing, deeply grooved and long philtrum, depressed and broad nasal bridge, bulbous tip of the nose, thick lower lip, thin upper lip, broad cheeks, and large ears and lobules. Recognition of this particular facial appearance was instrumental in the genetic diagnosis of 13q deletions and in the presymptomatic diagnosis of retinoblastoma in a significant number of our cases. Identification of this phenotype in a retinoblastoma patient allows for efficient diagnosis of recurrence in his progeny and/or sibship, while its ignorance will compromise genetic counseling due to the possible difficulties in detecting large deletions by standard molecular mutation analysis. Recognition of this syndrome in newborns without known familial risk for retinoblastoma is even more important as it is a clear warning sign that indicates immediate ophthalmic examination.

Retinoblastoma in Singapore: 1976 to 1995.

There were at least 56 local and 42 foreign patients seen in Singapore between 1976 and 1995 inclusively. The local incidence rate is 1 in 15789 live-births, and there appears to be no predilection for sex and race. Ninety-eight per cent presented before the age of five with the average age at diagnosis being 18 months. Bilateral cases were diagnosed earlier than unilateral cases. At least 17% are hereditary, with only 2 of these with positive family histories. Of the 41 patients studied for presenting complaints, 82.9% had leukocoria, 19.5% had strabismus and 12.2% had decreased visual acuity. The main mode of treatment was enucleation alone in unilateral disease; in bilateral cases, the main mode was enucleation of the more badly affected eye together with radiotherapy and cryotherapy of the fellow eye. Ninety per cent of all patients who underwent treatment have had enucleation done. Four patients defaulted treatment--with counselling of the parents of these patients, this number could be reduced or at least kept low. Patients with early diagnosis and treatment are more likely to survive. Eight of the 56 patients died. However, with better treatment modalities, the prognosis for both life and vision have, in recent years, improved significantly.