Disease progression model anchored around clinical diagnosis in longitudinal cohorts: example of Alzheimer's disease and related dementia

BACKGROUND

Alzheimer's disease and related dementia (ADRD) are characterized by multiple and progressive anatomo-clinical changes including accumulation of abnormal proteins in the brain, brain atrophy and severe cognitive impairment. Understanding the sequence and timing of these changes is of primary importance to gain insight into the disease natural history and ultimately allow earlier diagnosis. Yet, modeling changes over disease course from cohort data is challenging as the usual timescales (time since inclusion, chronological age) are inappropriate and time-to-clinical diagnosis is available on small subsamples of participants with short follow-up durations prior to diagnosis. One solution to circumvent this challenge is to define the disease time as a latent variable.

METHODS

We developed a multivariate mixed model approach that realigns individual trajectories into the latent disease time to describe disease progression. In contrast with the existing literature, our methodology exploits the clinical diagnosis information as a partially observed and approximate reference to guide the estimation of the latent disease time. The model estimation was carried out in the Bayesian Framework using Stan. We applied the methodology to the MEMENTO study, a French multicentric clinic-based cohort of 2186 participants with 5-year intensive follow-up. Repeated measures of 12 ADRD markers stemmed from cerebrospinal fluid (CSF), brain imaging and cognitive tests were analyzed.

RESULTS

The estimated latent disease time spanned over twenty years before the clinical diagnosis. Considering the profile of a woman aged 70 with a high level of education and APOE4 carrier (the main genetic risk factor for ADRD), CSF markers of tau proteins accumulation preceded markers of brain atrophy by 5 years and cognitive decline by 10 years. However we observed that individual characteristics could substantially modify the sequence and timing of these changes, in particular for CSF level of A[Formula: see text].

CONCLUSION

By leveraging the available clinical diagnosis timing information, our disease progression model does not only realign trajectories into the most homogeneous way. It accounts for the inherent residual inter-individual variability in dementia progression to describe the long-term anatomo-clinical degradations according to the years preceding clinical diagnosis, and to provide clinically meaningful information on the sequence of events.

TRIAL REGISTRATION

clinicaltrials.gov, NCT01926249. Registered on 16 August 2013.

Malignant hypercalcemia revealing a diffuse large B-cell lymphoma in a patient with a previous diagnosis of chronic myelomonocytic leukemia: An uncommon hematological coexistence

A 76-year-old patient previously admitted to the cardiology department for replacement of a right ventricular lead on a double-chamber pacemaker was admitted to the internal medicine department 15 days after for bronchopneumopathy. His past medical history was relevant for Type 2 diabetes mellitus, heart failure due to dilated hypokinetic heart disease, transcatheter aortic valve implantation (TAVI), and chronic myelomonocytic leukemia (CMML-0) diagnosed in 2021. Twenty-four hours after admission, the patient's general condition deteriorated abruptly, with the onset of drowsiness and psychomotor retardation. Laboratory exams revealed hypercalcemia at 4.18 mmol/L. Intensive hydration, calcitonin, and zoledronic acid were initiated and the patient was transferred to the nephrology intensive care unit where he underwent two sessions of hemodialysis to normalize serum calcium levels before readmission to internal medicine. Laboratory exams revealed low parathyroid hormone, normal 1-25-OH vitamin D, and increased parathyroid hormone-related peptide. Thoracoabdominal and positron emission tomography (PET) scan showed diffuse abdominopelvic peritoneal carcinosis associated with low-grade pleural effusion and multiple supra- and sub-diaphragmatic adenopathies, leading to a search for a solid tumor. The patient's clinical condition worsened leading to a transfer to the intensive care unit. The biopsy of a peritoneal carcinosis nodule confirmed the diagnosis of diffuse large B-cell lymphoma. Specific treatments were unsuccessful and the patient expired.

Associations among hypertension, dementia biomarkers, and cognition: The MEMENTO cohort

INTRODUCTION

Approximately 40% of dementia cases could be delayed or prevented acting on modifiable risk factors including hypertension. However, the mechanisms underlying the hypertension-dementia association are still poorly understood.

METHODS

We conducted a cross-sectional analysis in 2048 patients from the MEMENTO cohort, a French multicenter clinic-based study of outpatients with either isolated cognitive complaints or mild cognitive impairment. Exposure to hypertension was defined as a combination of high blood pressure (BP) status and antihypertensive treatment intake. Pathway associations were examined through structural equation modeling integrating extensive collection of neuroimaging biomarkers and clinical data.

RESULTS

Participants treated with high BP had significantly lower cognition compared to the others. This association was mediated by higher neurodegeneration and higher white matter hyperintensities load but not by Alzheimer's disease (AD) biomarkers.

DISCUSSION

These results highlight the importance of controlling hypertension for prevention of cognitive decline and offer new insights on mechanisms underlying the hypertension-dementia association.

HIGHLIGHTS

Paths of hypertension-cognition association were assessed by structural equation models. The hypertension-cognition association is not mediated by Alzheimer's disease biomarkers. The hypertension-cognition association is mediated by neurodegeneration and leukoaraiosis. Lower cognition was limited to participants treated with uncontrolled blood pressure. Blood pressure control could contribute to promote healthier brain aging.

How Selection Over Time Contributes to the Inconsistency of the Association Between Sex/Gender and Cognitive Decline Across Cognitive Aging Cohorts

The association between sex/gender and aging-related cognitive decline remains poorly understood because of inconsistencies in findings. Such heterogeneity could be attributable to the cognitive functions studied and study population characteristics, but also to differential selection by dropout and death between men and women. We aimed to evaluate the impact of selection by dropout and death on the association between sex/gender and cognitive decline. We first compared the statistical methods most frequently used for longitudinal data, targeting either population estimands (marginal models fitted by generalized estimating equations) or subject-specific estimands (mixed/joint models fitted by likelihood maximization) in 8 studies of aging: 6 population-based studies (the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) Study (1996-2009), Personnes Âgées QUID (PAQUID; 1988-2014), the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study (2003-2016), the Three-City Study (Bordeaux only; 1999-2016), the Washington Heights-Inwood Community Aging Project (WHICAP; 1992-2017), and the Whitehall II Study (2007-2016)) and 2 clinic-based studies (the Alzheimer's Disease Neuroimaging Initiative (ADNI; 2004-2017) and a nationwide French cohort study, MEMENTO (2011-2016)). We illustrate differences in the estimands of the association between sex/gender and cognitive decline in selected examples and highlight the critical role of differential selection by dropout and death. Using the same estimand, we then contrast the sex/gender-cognitive decline associations across cohorts and cognitive measures suggesting a residual differential sex/gender association depending on the targeted cognitive measure (memory or animal fluency) and the initial cohort selection. We recommend focusing on subject-specific estimands in the living population for assessing sex/gender differences while handling differential selection over time.

Personalized prediction of progression in pre-dementia patients based on individual biomarker profile: A development and validation study

INTRODUCTION

The prognosis of patients at the pre-dementia stage is difficult to define. The aim of this study is to develop and validate a biomarker-based continuous model for predicting the individual cognitive level at any future moment. In addition to personalized prognosis, such a model could reduce trial sample size requirements by allowing inclusion of a homogenous patient population.

METHODS

Disease-progression modeling of longitudinal cognitive scores of pre-dementia patients (baseline Clinical Dementia Rating ≤ 0.5) was used to derive a biomarker profile that was predictive of patient's cognitive progression along the dementia continuum. The biomarker profile model was developed and validated in the MEMENTO cohort and externally validated in the Alzheimer's Disease Neuroimaging Initiative.

RESULTS

Of nine candidate biomarkers in the development analysis, three cerebrospinal fluid and two magnetic resonance imaging measures were selected to form the final biomarker profile. The model-based prognosis of individual future cognitive deficit was shown to significantly improve when incorporating biomarker information on top of cognition and demographic data. In trial power calculations, adjusting the primary analysis for the baseline biomarker profile reduced sample size requirements by ≈10%. Compared to conventional cognitive cut-offs, inclusion criteria based on biomarker-profile cut-offs resulted in up to 28% reduced sample size requirements due to increased homogeneity in progression patterns.

DISCUSSION

The biomarker profile allows prediction of personalized trajectories of future cognitive progression. This enables accurate personalized prognosis in clinical care and better selection of patient populations for clinical trials. A web-based application for prediction of patients' future cognitive progression is available online.

Cost comparison of reusable and disposable air/water syringe tips in a large French teaching hospital

Air/water syringe (AWS) tips can be used in any type of dental care. They may be disposable (plastic) or reusable (stainless steel or plastic). We assessed the costs of using both sorts of tips in a French teaching hospital. A systematic use of one AWS tip per dental consultation was considered. Consultations performed with reusable AWS (stainless steel) tips give rise to costs linked to initial purchase of tips, their sterilisation, and replacement. Consultation costs of disposable AWS tips were calculated at their current purchase price. Replacing reusable tips was evaluat-ed in two different situations: annual replacement or replacement in case of visual deterioration. Results showed that the number of consultations must lie beyond a certain threshold in order to make reusable tips more economical in use than disposable counterparts. If the reusable tips are replaced every year, this threshold is higher (e.g.: 1,366consultations at the University of Bordeaux) than under a rule of tip replacement in case of visual deterioration (e.g. at the Bordeaux University: 1,267consultations in case of an annual replacement rate of 10%, or 1,289 with a re-placement rate of 30%). This is the first study regarding the costs of disposable versus reusable AWS tips. We suggest that disposable tips might be more cost-effective than reusable tips, not-ably because of their reduced risk of crosscontamination. The choice of the use of one or an-other AWS tip crucially depends on the number of consultations, as well as on their practical utilisation and on infection control issues.

Genetic counselling difficulties and ethical implications of incidental findings from array-CGH: a 7-year national survey

Microarray-based comparative genomic hybridization (aCGH) is commonly used in diagnosing patients with intellectual disability (ID) with or without congenital malformation. Because aCGH interrogates with the whole genome, there is a risk of being confronted with incidental findings (IF). In order to anticipate the ethical issues of IF with the generalization of new genome-wide analysis technologies, we questioned French clinicians and cytogeneticists about the situations they have faced regarding IF from aCGH. Sixty-five IF were reported. Forty corresponded to autosomal dominant diseases with incomplete penetrance, 7 to autosomal dominant diseases with complete penetrance, 14 to X-linked diseases, and 4 were heterozygotes for autosomal recessive diseases with a high prevalence of heterozygotes in the population. Therapeutic/preventive measures or genetic counselling could be argued for all cases except four. These four IF were intentionally not returned to the patients. Clinicians reported difficulties in returning the results in 29% of the cases, mainly when the question of IF had not been anticipated. Indeed, at the time of the investigation, only 48% of the clinicians used consents mentioning the risk of IF. With the emergence of new technologies, there is a need to report such national experiences; they show the importance of pre-test information on IF.

A French collaborative survey of 272 fetuses with 22q11.2 deletion: ultrasound findings, fetal autopsies and pregnancy outcomes

OBJECTIVE

The 22q11.2 deletion (del22q11.2) is one of the most common microdeletions. We performed a collaborative, retrospective analysis in France of prenatal diagnoses and outcomes of fetuses carrying the del22q11.2.

METHODS

A total of 272 fetuses were included. Data on prenatal diagnosis, ultrasound findings, pathological features, outcomes and inheritance were analyzed.

RESULTS

The mean time of prenatal diagnosis was 25.6 ± 6 weeks of gestation. Most of the diagnoses (86.8%) were prompted by abnormal ultrasound findings [heart defects (HDs), in 83.8% of cases]. On fetal autopsy, HDs were again the most common disease feature, but thymus, kidney abnormalities and facial dysmorphism were also described. The deletion was inherited in 27% of cases. Termination of pregnancy (TOP) occurred in 68.9% of cases and did not appear to depend on the inheritance status. However, early diagnosis was associated with a higher TOP rate.

CONCLUSION

This is the largest cohort of prenatal del22q11.2 diagnoses. As in postnatally diagnosed cases, HDs were the most frequently observed abnormalities. However, thymus and kidney abnormalities and polyhydramnios should also be screened for in the prenatal diagnosis of del22q11.2. Only the time of diagnosis appeared to be strongly associated with the pregnancy outcome: the earlier the diagnosis, the higher the TOP rate.

Array-CGH Analysis Suggests Genetic Heterogeneity in Rhombencephalosynapsis

Rhombencephalosynapsis is an uncommon, but increasingly recognized, cerebellar malformation defined as vermian agenesis with fusion of the hemispheres. The embryologic and genetic mechanisms involved are still unknown, and to date, no animal models are available. In the present study, we used Agilent oligonucleotide arrays in a large series of 57 affected patients to detect candidate genes. Four different unbalanced rearrangements were detected: a 16p11.2 deletion, a 14q12q21.2 deletion, an unbalanced translocation t(2p;10q), and a 16p13.11 microdeletion containing 2 candidate genes. These genes were further investigated by sequencing and in situ hybridization. This first microarray screening of a rhombencephalosynapsis series suggests that there may be heterogeneous genetic causes.

Renal insufficiency, a frequent complication with age in oral-facial-digital syndrome type I

The oral-facial-digital syndrome type I (OFD I) is characterized by multiple congenital malformations of the face, oral cavity and digits. A polycystic kidney disease (PKD) is found in about one-third of patients but long-term outcome and complications are not well described in the international literature. Renal findings have been retrospectively collected in a cohort of 34 females all carrying a pathogenic mutation in the OFD1 gene with ages ranging from 1 to 65 years. Twelve patients presented with PKD - 11/16 (69%) if only adults were considered -with a median age at diagnosis of 29 years [IQR (interquartile range) = (23.5-38)]. Among them, 10 also presented with renal impairment and 6 were grafted (median age = 38 years [IQR = (25-48)]. One grafted patient under immunosuppressive treatment died from a tumor originated from a native kidney. The probability to develop renal failure was estimated to be more than 50% after the age of 36 years. Besides, neither genotype-phenotype correlation nor clinical predictive association with renal failure could be evidenced. These data reveal an unsuspected high incidence rate of the renal impairment outcome in OFD I syndrome. A systematic ultrasound (US) and renal function follow-up is therefore highly recommended for all OFD I patients.

Breakpoint characterization: a new approach for segregation analysis of paracentric inversion in human sperm

Paracentric inversions (PAI) are structural chromosomal rearrangements generally considered to be harmless. Nevertheless, cases of viable recombinants have been reported, indicating the interest of studying the meiotic behaviour of these chromosomal abnormalities. To date, the few studies reported have been performed using either the human-hamster fertilization system or fluorescence in situ hybridization with centromeric or telomeric DNA probes. In order to improve the assessment of meiotic segregation in PAI, we present a new strategy based on the use of bacterial artificial chromosome (BAC) probes which allow a precise localization of chromosome breakpoints and the identification of all meiotic products in human sperm. Sperm samples from carriers of an inv(5) and an inv(14) were used to test this new high-resolution procedure.

Fluorescence in situ hybridization analysis of 110 hematopoietic disorders with chromosome 5 abnormalities: do de novo and therapy-related myelodysplastic syndrome-acute myeloid leukemia actually differ?

A retrospective cytogenetic study of acute myeloid leukemias (AML) and myelodysplastic syndromes (MDS) was conducted by the Groupe Francophone de Cytogénétique Hématologique (GFCH) to evaluate the structural abnormalities of chromosome 5 associated with other chromosomal abnormalities, in particular of chromosome 7, in these pathologies. In all, 110 cases of AML/MDS were recruited based on the presence of chromosome 5 abnormalities under conventional cytogenetics and supplemented by a systematic fluorescence in situ hybridization study of chromosomes 5 and 7. The abnormalities of the long arm of chromosome 5 (5q) were deletions of various sizes and sometimes cryptic. The 5q abnormalities were associated with translocations in 54% of cases and were simple deletions in 46%. In 68% of cases, 5q deletions were associated with chromosome 7 abnormalities, and 90% of these presented a complex karyotype. Of the 110 patients, 28 had a hematopoietic disorder secondary to chemotherapy, radiotherapy, or both. Among 82 patients with de novo AML/MDS, 63 were older than 60 years. Chromosomal abnormalities often associated hypodiploidy and chromosome 5 and 7 abnormalities in complex karyotypes, features resembling those of secondary hemopathies. Systematic investigation of the exposure to mutagens and oncogenes is thus essential to specify the factors potentially involved in MDS/AML with 5q abnormalities.

Specific language impairment as the prominent feature in a patient with a low-level trisomy 21 mosaicism

BACKGROUND

The extent and severity of the disabilities is variable among individuals with Down syndrome, although generally characterized by a range of physical and intellectual conditions, including language impairment. Whether the language deficit is due to the intellectual disability (ID) or associated to the supernumerary or portion of chromosome 21 is still debated.

METHODS

Karyotyping was performed on blood lymphocyte and skin fibroblasts. Fluorescence in situ hybridization analysis was performed on cultured lymphocytes and buccal smear cells.

RESULTS

The trisomy 21 (T21) mosaicism was characterized by 0.7-10% of mosaic cells in the different tissues, in a 14-year-old girl presenting an intellectual development within the normal range and specific language impairment (SLI) as the only prominent feature.

CONCLUSION

This case illustrates the wide range of phenotypical abnormalities possibly associated with T21 mosaicism. We propose that SLI is indeed a phenotypic trait specific to Down syndrome rather than subsequent to the ID most often associated to the syndrome.

Rare Robertsonian translocations and meiotic behaviour: sperm FISH analysis of t(13;15) and t(14;15) translocations: a case report

t(13;15) and t(14;15) are two rare Robertsonian translocations. Meiotic segregation was studied in four males heterozygous for the rare Robertsonian translocations t(13;15) and t(14;15). Both locus-specific probes (LSPs) and whole chromosome painting (WCP) probes, specific to chromosomes 13, 14 and 15, were used in this study. The number of spermatozoa scored for each carrier ranged from 891 to 5000. The frequencies of normal and balanced sperm resulting from the alternate mode of segregation ranged from 77.6 to 92.8%, confirming the prevalence of alternate segregation over other segregation modes in all Robertsonian translocations. The incidences of unbalanced complements ranged from 6.7 to 20.4%, with a significant excess of disomy rates over the complementary frequencies of nullisomy. This variability might reflect differences in the location of breakpoints in translocated chromosomes, leading to the variable production of unbalanced gametes and the variable alterations of semen parameters in Robertsonian translocation carriers.

Mutations in PHF8 are associated with X linked mental retardation and cleft lip/cleft palate

Truncating mutations were found in the PHF8 gene (encoding the PHD finger protein 8) in two unrelated families with X linked mental retardation (XLMR) associated with cleft lip/palate (MIM 300263). Expression studies showed that this gene is ubiquitously transcribed, with strong expression of the mouse orthologue Phf8 in embryonic and adult brain structures. The coded PHF8 protein harbours two functional domains, a PHD finger and a JmjC (Jumonji-like C terminus) domain, implicating it in transcriptional regulation and chromatin remodelling. The association of XLMR and cleft lip/palate in these patients with mutations in PHF8 suggests an important function of PHF8 in midline formation and in the development of cognitive abilities, and links this gene to XLMR associated with cleft lip/palate. Further studies will explore the specific mechanisms whereby PHF8 alterations lead to mental retardation and midline defects.

Six cases of cryptic subtelomeric translocations in four families: the use of subtelomeric FISH probes as a diagnostic tool

Finding the diagnosis in children with mental retardation and a normal karyotype, whether or not associated with dysmorphic features, is important for defining an eventual syndrome and for genetic counselling of the families. Telomeric re-arrangements may be a common and underestimated-to-date cause of non-syndromic mental retardation. Using a FISH-based approach combining subtelomeric probes, we report the detection of 4 cases of cryptic translocations t(2;10)(p25.3;q26.3), t(4;17)(p16.2;q25), t(4;20)(p16.2;q13) and t(5;7)(p15.3;q36) associated with MR and dysmorphic features. We discuss the usefulness of subtelomeric FISH in children with unexplained delayed psychomotor development, when the genetic cause remains unknown and the karyotype is normal.

[Molecular chromosomic genetics in prenatal and perinatal diagnosis of chromosomal anomalies and genetic diseases]

Prenatal and perinatal diagnosis needs a rapid, accurate and overall genome analysis. Molecular chromosomic techniques such as fluorescent in situ hybridization (FISH) with "cold" (not radioactively labeled) probes combine techniques of both conventional chromosome banding and molecular biology. FISH is a powerful tool for detecting some genetic diseases as well as microscopic or submicroscopic chromosome rearrangements, in metaphases cells or interphase nuclei.

Chromosomal instability in two siblings with gonad deficiency: case report

Non-random de novo autosomal chromosomal rearrangements have not been shown to cause exocrine or gonadal dysfunction. We report on two siblings, a brother and a sister, both with de novo chromosomal rearrangements and gonadal deficiency including premature ovarian failure. They had normal phenotypes without additional manifestations of known chromosomal breakage syndromes (except for the gonadal dysfunction) and normal alpha-fetoprotein dosage level. The association of sperm abnormalities in the brother and ovarian dysfunction in the sister suggested an increased spontaneous chromosomal instability. Since the co-occurrence of chromosomal anomalies and reproductive failures may not be coincidental, we performed repeated chromosomal analysis of peripheral blood lymphocytes prior to proposing ICSI for IVF (for the brother). In both sibs, infertility was associated with random and non-random de novo autosomal chromosomal abnormalities. We discuss the possible relationship between these unusual clinical and cytogenetic features and their potential links to ataxia-telangiectasia.

Balanced complex chromosomal rearrangements (BCCR) with at least three chromosomes and three or more breakpoints: report of three new cases

Balanced complex chromosomal rearrangements (BCCR) encompass a heterogeneous group of rare chromosomal aberrations. In this paper, we report three cases of BCCRs. In two the probands were referred for either genetic counseling or prenatal management. One case was ascertained after chromosome analysis performed because of psychiatric manifestations; this was an isolated finding. We also outline the molecular cytogenetic techniques, which were essential in confirming and precisely delineating the BCCRs identified in these patients. In addition the various aspects of genetic counseling for this type of chromosomal rearrangement, highlighting the details particular to each individual case are discussed. We discuss the classification for this type of chromosomal mutation.

A balanced complex chromosomal rearrangement (BCCR) in a family with reproductive failure

Balanced complex chromosomal rearrangements are very rare events in the human population. Translocations involving three or more chromosomes frequently lead to a severe reproductive impairment secondary to meiotic disturbance in males and to chromosomal imbalance in gametes of females. We report a new familial case of complex chromosome anomaly involving chromosomes 13, 14 and 22. Cytogenetic investigations showed a complex chromosomal chromosome rearrangement involving: (i) a Robertsonian translocation between chromosomes 13 and 14; and (ii) a reciprocal translocation between the long arms of chromosome 14 and the long arm of chromosome 22. The aetiology of the translocation was characterized by conventional fluorescence in-situ hybridization (FISH) studies and routine R- and G-banding (RTBG and GBTG) combined with alpha and beta satellite centromeric FISH probes. Predicted configuration of the hexavalent at pachytene stage of meiosis was used to consider the modes of segregation; only two configurations resulted in a normal or balanced gamete karyotype. Reproductive management and genetic counselling are discussed.

French multi-centric study of 2000 amniotic fluid interphase FISH analyses from high-risk pregnancies and review of the literature

This prospective and multi-centric study confirms the accuracy and the limitations of interphase FISH and shows that any cytogenetics laboratory can perform this technique. With regard to the technical approach, we think that slides must be examined by two investigators, because the scoring may be subjective. The main problem with the AneuVysion kit concerns the alpha satellite probes, and especially the chromosome 18 probe, which is sometimes very difficult to interpret because of the high variability of the size of the spots, and this may lead to false negative and uninformative cases. The best solution would be to replace these probes by locus-specific probes. Concerning clinical management, we offer interphase FISH only in very high-risk pregnancies or/and at late gestational age because of the cost of the test. We think that an aberrant FISH result can be used for a clinical decision when it is associated with a corresponding abnormal ultrasound scan. In other cases, most of the time, we prefer to wait for the standard karyotype.

A multicentric study of 41 cases of B-prolymphocytic leukemia: two evolutive forms

B-prolymphocytic leukemia (B-PLL) is an infrequent disease with a poor prognosis. We present the clinical and biological features of 41 patients. Median age was 67 years [42-89] and male-female sex ratio was 2.4. The immunophenotyping revealed B-cell phenotype, with a high level expression of surface IgM and/or IgD in all cases, FMC7+ in 76 % of cases and CD5+ in 67%. Marked spontaneous in-vitro apoptosis was observed in most cases tested (n = 12). The median overall survival time was 5 years and the event-free survival time was 37 months. As detected by univariate and multivariate analysis, the only variables associated with a poor prognosis were advanced age and anemia. No significant difference was observed between de novo PLL (n = 27) and prolymphocytoid transformation of chronic lymphocytic leukemia (n = 14). Two groups of patients were individualized according to their clinical course: patients who died within one year of diagnosis (n = 14) and patients who had a prolonged survival (n = 23) without any treatment in some cases. The comparison between the 2 groups showed that they differed in age (p = 0.01) and anemia (p = 0.02). We also observed that the patients with p53 mutations had a worse clinical outcome. Taken together these data confirm that B-PLL should be regarded as a distinct form of chronic lymphoproliferative disorder and suggest the existence of two patterns of clinical evolution.

A case of (X;15) translocation diagnosed as a paracentric inversion of Xp: diagnostic revision with FISH

In 1990 we reported the case of a 17 years old girl with growth retardation, overweight and primary amenorrhea, presenting a de novo chromosomal rearrangement cytogenetically characterized as a paracentric inversion of the short arm of X chromosome. The FISH analyses that were recently performed, revealed that in fact our patient presented a case of unbalanced translocation, 46,X, t(X;15)(p11.2; q15).

Identification of human candidate genes for male infertility by digital differential display

Evidence for the importance of genetic factors in male fertility is accumulating. In the literature and the Mendelian Cytogenetics Network database, 265 cases of infertile males with balanced reciprocal translocations have been described. The candidacy for infertility of 14 testis-expressed transcripts (TETs) were examined by comparing their chromosomal mapping position to the position of balanced reciprocal translocation breakpoints found in the 265 infertile males. The 14 TETs were selected by using digital differential display (electronic subtraction) to search for apparently testis-specific transcripts in the TIGR database. The testis specificity of the 14 TETs was further examined by reverse transcription-polymerase chain reaction (RT-PCR) on adult and fetal tissues showing that four TETs (TET1 to TET4) were testis-expressed only, six TETs (TET5 to TET10) appeared to be differentially expressed and the remaining four TETs (TET11 to TET14) were ubiquitously expressed. Interestingly, the two tesis expressed-only transcripts, TET1 and TET2, mapped to chromosomal regions where seven and six translocation breakpoints have been reported in infertile males respectively. Furthermore, one ubiquitously, but predominantly testis-expressed, transcript, TET11, mapped to 1p32-33, where 13 translocation breakpoints have been found in infertile males. Interestingly, the mouse mutation, skeletal fusions with sterility, sks, maps to the syntenic region in the mouse genome. Another transcript, TET7, was the human homologue of rat Tpx-1, which functions in the specific interaction of spermatogenic cells with Sertoli cells. TPX-1 maps to 6p21 where three cases of chromosomal breakpoints in infertile males have been reported. Finally, TET8 was a novel transcript which in the fetal stage is testis-specific, but in the adult is expressed in multiple tissues, including testis. We named this novel transcript fetal and adult testis-expressed transcript (FATE).

High resolution comparative genomic hybridisation analysis reveals imbalances in dyschromosomal patients with normal or apparently balanced conventional karyotypes

A sensitive technique is needed for screening whole genome imbalances in dyschromosomal patients when G-banding shows normal karyotypes or apparently balanced translocations. In this study we performed highly sensitive comparative genomic hybridisation analysis on a number of such cases and revealed chromosomal imbalances in all.

Two unrelated patients with inversions of the X chromosome and non-specific mental retardation: physical and transcriptional mapping of their common breakpoint region in Xq13.1

Two unrelated mildly retarded males with inversions of the X chromosome and non-specific mental retardation (MRX) are described. Case 1 has a pericentric inversion 46,Y,inv(X) (p11.1q13.1) and case 2 a paracentric inversion 46,Y,inv(X) (q13.1q28). Both male patients have severe learning difficulties. The same chromosomal abnormalities were found in their mothers who are intellectually normal. Fluorescence in situ hybridisation mapping showed a common area of breakage of each of the inverted chromosomes in Xq13.1 near DXS131 and DXS162. A detailed long range restriction map of the breakpoint region was constructed using YAC, PAC, and cosmid clones. We show that the two inverted chromosomes break within a short 250 kb region. Moreover, a group of ESTs corresponding to an as yet uncharacterised gene was mapped to the same critical interval. We hypothesise that the common inversion breakpoint region of the two cases in Xq13.1 may contain a new MRX gene.

Phenotypic and genotypic variability in monozygotic triplets with Turner syndrome

Turner syndrome (TS) is a common disorder (1/2500 and 1/5000 female births) which is diagnosed at birth in approximately 20% of patients and during childhood (usually due to growth retardation) or later, (due to lack of pubertal development) for the remaining patients. Here we present a cytogenetic and molecular analysis of three monozygotic sisters. The diagnosis of TS was done for one of them (patient 1) who presented with a typical Turner phenotype. A first karyotype was established as normal and a second karyotype (carried out on 200 cells) revealed a 45,X/46,XX mosaicism with 6% of cells with a 45,X karyotype. Lymphocyte karyotype analysis showed the same mosaicism pattern for the two other sisters, one of them exhibiting only a mild (patient 2) and the other no clinical features of Turner syndrome (patient 3). Karyotype analysis was this time conducted on fibroblasts and showed that the 45,X/46,XX mosaicism pattern correlated with the clinical phenotype with 99, 43 and 3% of 45,X cells in patients 1, 2, and 3, respectively. These data suggest that different tissues other than lymphocytes should be subjected to a karyotype analysis when the observed genotype does not correlate with the clinical phenotype.

[Unusual presentation of nephroblastomatosis]

BACKGROUND

Nephrogenic rests generally constitute precursor lesions of Wilms' tumor. We report a case of right nephroblastomatosis with dysmorphic features.

CASE REPORT

An enlargement of the right kidney was incidentally discovered in a 1-year-old girl with dysmorphic features but normal psychomotor development. Combined ultrasonography and computerized tomography (CT) scan showed right cortical nephroblastomatosis. Chemotherapy using actinomycin D and vincristin was successful; however, an hyperechogenic nodule was subsequently found, necessitating a right nephrectomy.

CONCLUSION

The relationship between nephroblastomatosis and Wilms' tumor is discussed. This case report reminds us of the importance of a long-term follow-up including echography and CT scan in cases of nephroblastomatosis.

Application of fluorescence in situ hybridization to the identification of different marker chromosomes

Chromosome studies performed on lymphocyte culture of a baby with specific dysmorphism and congenital anomalies suggestive of trisomy 21 revealed a mosaicism: 46,XY,rea(21q21q) [25]/47,XY,rea(21q21q),+mar1[25]. The karyotype of the mother is normal, but the father's karyotype presents an supernumerary chromosome greater and different from the marker of his son: 47,XY,+mar2 (100%). The identification of the two marker chromosomes by standard cytogenetic techniques followed by molecular techniques is essential for the identification of the origin of these two chromosomes. The unusual presence of two different markers one in the father and one in the son, as well as the clinical features of the child, are presented. The possible role of the paternal marker, in the de novo chromosomal rearrangement in his child will be discussed.

[Ultrasound abnormalities of the placenta during triploidy with pre-eclampsia in the 2nd trimester]

A documented case of triploidism which developed to 20 weeks gestation underlines the importance of early ultrasonographic assessment of the trophoblast. Large placentas, especially when pre-eclampsia occurs, should lead to assay of beta-hCG and search for chromosome anomalies. Paternal genomic origin was suggested based on the large volume of the placenta.

A large multiple endocrine neoplasia type 1 family with clinical expression suggestive of anticipation

We describe a large multigenerational multiple endocrine neoplasia Type 1 (MEN1) family with clinical expression suggestive of anticipation. In the second and third generations, two deceased obligate gene carriers died at the ages of 85 and 76 without the history of MEN1, whereas two other living gene carriers above the age of 65 have had no clinical evidence of MEN1 to date. In the fourth generation, eight members were affected, with four having severe MEN1-related and atypical malignancies: a case of metastatic endocrine pancreatic tumor, two cases of metastatic thymic carcinoids, and a case of spinal ependymoma. In the fifth generation, all five patients were below the age of 22 when the disease was detected. MEN1 was confirmed in the family by linkage analysis using MEN1-linked microsatellite markers and by identification of a nonsense mutation in the MEN1/menin gene. Alleotyping showed loss of heterozygosity (LOH) involving the wild-type alleles in seven tumors in the family including the ependymoma, which is the first MEN1-related case that shows genetic abnormality in chromosome 11q13, suggesting that MEN1 gene might be involved in the tumorigenesis of a subset of ependymomas. In relation to clinical anticipation, repeated expansion studies were carried out but failed to detect any expansion. We conclude that this is a unique MEN1 family and that an unknown genetic mechanism might be contributing to the anticipation phenomenon. We demonstrate in this family that all gene carriers, including the very young members, will need close and careful follow-up.

Meiotic segregation in males heterozygote for reciprocal translocations: analysis of sperm nuclei by two and three colour fluorescence in situ hybridization

The meiotic segregation of chromosomes was analysed in three reciprocal translocation carriers, using FISH on interphase spermatozoa. The segregation pattern was first studied in 27,844 spermatozoa from two siblings carrying the reciprocal translocation t(6;11)(q14;p14). Three centromeric probes, specific for chromosomes 6, 11 and 1, were simultaneously hybridized so that all centric fragments as well as the ploidy of each cell could be determined by three colour FISH. For both subjects, the respective frequencies of alternate/adjacent 1, adjacent 2, 3:1 and 4:0 segregation modes were 88%, 9%, 3+ and < 1%. In another reciprocal translocation t(2;14)(p23.1;q31), a two colour FISH analysis was performed on 4,610 spermatozoa, using a chromosome 2 centromeric probe and a YAC probe located on the centric fragment of chromosome 14. Frequencies of alternate/adjacent 1, adjacent 2, and 3:1 segregations were 89%, 5.2%, and 5.8% respectively. The segregation of chromosomes X, Y and 1 were also analyzed with three colour FISH on the spermatozoa from all three translocation carriers, in order to detect an interchromosomal effect. Aneuploidy rates for the X and Y chromosomes were found to be in the same range in the three translocation carriers and control donors, but disomy 1 rates were slightly increased in the translocation carriers.