Genetic screening for maternal uniparental disomy of chromosome 7 in prenatal and postnatal growth retardation of unknown cause

Case Report: Expressive Speech Disorder in a Family as a Hallmark of 7q31 Deletion Involving the FOXP2 Gene

Pathogenic variants of FOXP2 gene were identified first as a monogenic cause of childhood apraxia of speech (CAS), a complex disease that is associated with an impairment of the precision and consistency of movements underlying speech, due to deficits in speech motor planning and programming. FOXP2 variants are heterogenous; single nucleotide variants and small insertions/deletions, intragenic and large-scale deletions, as well as disruptions by structural chromosomal aberrations and uniparental disomy of chromosome 7 are the most common types of mutations. FOXP2-related speech and language disorders can be classified as "FOXP2-only," wherein intragenic mutations result in haploinsufficiency of the FOXP2 gene, or "FOXP2-plus" generated by structural genomic variants (i.e., translocation, microdeletion, etc.) and having more likely developmental and behavioral disturbances adjacent to speech and language impairment. The additional phenotypes are usually related to the disruption/deletion of multiple genes neighboring FOXP2 in the affected chromosomal region. We report the clinical and genetic findings in a family with four affected individuals having expressive speech impairment as the dominant symptom and additional mild dysmorphic features in three. A 7.87 Mb interstitial deletion of the 7q31.1q31.31 region was revealed by whole genome diagnostic microarray analysis in the proband. The FOXP2 gene deletion was confirmed by multiplex ligation-dependent probe amplification (MLPA), and all family members were screened by this targeted method. The FOXP2 deletion was detected in the mother and two siblings of the proband using MLPA. Higher resolution microarray was performed in all the affected individuals to refine the extent and breakpoints of the 7q31 deletion and to exclude other pathogenic copy number variants. To the best of our knowledge, there are only two family-studies reported to date with interstitial 7q31 deletion and showing the core phenotype of FOXP2 haploinsufficiency. Our study may contribute to a better understanding of the behavioral phenotype of FOXP2 disruptions and aid in the identification of such patients. We illustrate the importance of a targeted MLPA analysis suitable for the detection of FOXP2 deletion in selected cases with a specific phenotype of expressive speech disorder. The "phenotype first" and targeted diagnostic strategy can improve the diagnostic yield of speech disorders in the routine clinical practice.

Diagnosis and management of Silver-Russell syndrome: first international consensus statement

This Consensus Statement summarizes recommendations for clinical diagnosis, investigation and management of patients with Silver-Russell syndrome (SRS), an imprinting disorder that causes prenatal and postnatal growth retardation. Considerable overlap exists between the care of individuals born small for gestational age and those with SRS. However, many specific management issues exist and evidence from controlled trials remains limited. SRS is primarily a clinical diagnosis; however, molecular testing enables confirmation of the clinical diagnosis and defines the subtype. A 'normal' result from a molecular test does not exclude the diagnosis of SRS. The management of children with SRS requires an experienced, multidisciplinary approach. Specific issues include growth failure, severe feeding difficulties, gastrointestinal problems, hypoglycaemia, body asymmetry, scoliosis, motor and speech delay and psychosocial challenges. An early emphasis on adequate nutritional status is important, with awareness that rapid postnatal weight gain might lead to subsequent increased risk of metabolic disorders. The benefits of treating patients with SRS with growth hormone include improved body composition, motor development and appetite, reduced risk of hypoglycaemia and increased height. Clinicians should be aware of possible premature adrenarche, fairly early and rapid central puberty and insulin resistance. Treatment with gonadotropin-releasing hormone analogues can delay progression of central puberty and preserve adult height potential. Long-term follow up is essential to determine the natural history and optimal management in adulthood.

Accurate Breakpoint Mapping in Apparently Balanced Translocation Families with Discordant Phenotypes Using Whole Genome Mate-Pair Sequencing

Familial apparently balanced translocations (ABTs) segregating with discordant phenotypes are extremely challenging for interpretation and counseling due to the scarcity of publications and lack of routine techniques for quick investigation. Recently, next generation sequencing has emerged as an efficacious methodology for precise detection of translocation breakpoints. However, studies so far have mainly focused on de novo translocations. The present study focuses specifically on familial cases in order to shed some light to this diagnostic dilemma. Whole-genome mate-pair sequencing (WG-MPS) was applied to map the breakpoints in nine two-way ABT carriers from four families. Translocation breakpoints and patient-specific structural variants were validated by Sanger sequencing and quantitative Real Time PCR, respectively. Identical sequencing patterns and breakpoints were identified in affected and non-affected members carrying the same translocations. PTCD1, ATP5J2-PTCD1, CADPS2, and STPG1 were disrupted by the translocations in three families, rendering them initially as possible disease candidate genes. However, subsequent mutation screening and structural variant analysis did not reveal any pathogenic mutations or unique variants in the affected individuals that could explain the phenotypic differences between carriers of the same translocations. In conclusion, we suggest that NGS-based methods, such as WG-MPS, can be successfully used for detailed mapping of translocation breakpoints, which can also be used in routine clinical investigation of ABT cases. Unlike de novo translocations, no associations were determined here between familial two-way ABTs and the phenotype of the affected members, in which the presence of cryptic imbalances and complex chromosomal rearrangements has been excluded. Future whole-exome or whole-genome sequencing will potentially reveal unidentified mutations in the patients underlying the discordant phenotypes within each family. In addition, larger studies are needed to determine the exact percentage for phenotypic risk in families with ABTs.

Differentially methylated regions in maternal and paternal uniparental disomy for chromosome 7

DNA methylation is a hallmark of genomic imprinting and differentially methylated regions (DMRs) are found near and in imprinted genes. Imprinted genes are expressed only from the maternal or paternal allele and their normal balance can be disrupted by uniparental disomy (UPD), the inheritance of both chromosomes of a chromosome pair exclusively from only either the mother or the father. Maternal UPD for chromosome 7 (matUPD7) results in Silver-Russell syndrome (SRS) with typical features and growth retardation, but no gene has been conclusively implicated in SRS. In order to identify novel DMRs and putative imprinted genes on chromosome 7, we analyzed eight matUPD7 patients, a segmental matUPD7q31-qter, a rare patUPD7 case and ten controls on the Infinium HumanMethylation450K BeadChip with 30 017 CpG methylation probes for chromosome 7. Genome-scale analysis showed highly significant clustering of DMRs only on chromosome 7, including the known imprinted loci GRB10, SGCE/PEG10, and PEG/MEST. We found ten novel DMRs on chromosome 7, two DMRs for the predicted imprinted genes HOXA4 and GLI3 and one for the disputed imprinted gene PON1. Quantitative RT-PCR on blood RNA samples comparing matUPD7, patUPD7, and controls showed differential expression for three genes with novel DMRs, HOXA4, GLI3, and SVOPL. Allele specific expression analysis confirmed maternal only expression of SVOPL and imprinting of HOXA4 was supported by monoallelic expression. These results present the first comprehensive map of parent-of-origin specific DMRs on human chromosome 7, suggesting many new imprinted sites.

Early developmental influences on hepatic organogenesis

The liver is the largest of the body's organs, with the greatest number of functions, playing a central role in coordinating metabolic homeostasis, nutrient processing and detoxification. The fetal liver forms during early gestation in response to a sequential array of distinct biological events, regulated by intrinsically programmed mechanisms and extracellular signals which instruct hepatic cells to either proliferate, differentiate or undergo apoptosis. A vast number of genes are involved in the initiation and control of liver development, many of which are sensitive to nutritional and hormonal regulation in utero. Moreover, liver mass is influenced by the gestational environment. Therefore, during periods of hepatic cell proliferation and differentiation, the developing fetal liver is sensitive to damage from both internal and external sources including teratogens, infection and nutritional deficiencies. For example, fetuses exposed to decreased materno-fetal nutrition during late gestation have a reduced liver mass, and/or perturbed liver function, which includes increased plasma LDL cholesterol and fibrinogen concentrations. These occur in conjunction with other risk factors present in the early stages of cardiovascular disease i.e. decreased glucose tolerance and insulin insensitivity in later life. Taken together, these findings suggest that liver mass, and later function, are essentially set in utero during fetal development-a process that is ultimately regulated by the intrauterine environment.

Atypical Silver-Russell phenotype resulting from maternal uniparental disomy of chromosome 7

We report on a patient with atypical Silver-Russell phenotype comprising severe growth retardation, unusual facies, bilateral Duane anomaly and infantile hypercalcemia caused by maternal uniparental iso/heterodisomy (mUPD) of chromosome 7. The development of myoclonus in this patient lends further support to the hypothesis that abnormal imprinting of the SGCE gene is responsible for some cases of myoclonus-dystonia syndrome. This case highlights the utility of SNP microarray technology as an accessible tool for the diagnosis of mUPD7 in atypical cases. We propose that depending on the balance of iso- and heterodisomic segments in a particular patient, mUPD7 may result in a range of phenotypes not confined to classic Silver-Russell syndrome.

Recessive congenital myotonia resulting from maternal isodisomy of chromosome 7: a case report

Autosomal dominant (Thomsen) and recessive (Becker) congenital myotonia are two different non dystrophic disorders, due to allelic mutations of the muscle chloride channel gene, located on chromosome 7q35. More than two thirds of the muscle chloride channel gene mutations occur independently in unique families and cause the recessive form of the disease. Becker disease is more common and severe than Thomsen disease. Here, we report on the clinical and molecular data of the first patient with maternal uniparental disomy for chromosome 7 and recessive congenital myotonia. The proband is a 15-year-old male, homozygous for a missense mutation within muscle chloride channel gene, showing few characteristic signs of the Silver Russell Syndrome.

Recessive congenital myotonia resulting from maternal isodisomy of chromosome 7: a case report

Autosomal dominant (Thomsen) and recessive (Becker) congenital myotonia are two different non dystrophic disorders, due to allelic mutations of the muscle chloride channel gene, located on chromosome 7q35. More than two thirds of the muscle chloride channel gene mutations occur independently in unique families and cause the recessive form of the disease. Becker disease is more common and severe than Thomsen disease. Here, we report on the clinical and molecular data of the first patient with maternal uniparental disomy for chromosome 7 and recessive congenital myotonia. The proband is a 15-year-old male, homozygous for a missense mutation within muscle chloride channel gene, showing few characteristic signs of the Silver Russell Syndrome.

Clinically distinct epigenetic subgroups in Silver-Russell syndrome: the degree of H19 hypomethylation associates with phenotype severity and genital and skeletal anomalies

CONTEXT

The H19 imprinting control region (ICR), located on chromosome 11p15.5, has been reported hypomethylated in 20-65% of Silver-Russell syndrome (SRS) patients.

OBJECTIVE

We investigated the methylation status of 11p15.5 ICRs in SRS patients and children born small for gestational age (SGA) to clarify the relationship between phenotype and H19 methylation status.

METHODS

We performed methylation screens of the H19 and KCNQ1OT1 ICRs in 42 SRS patients, including seven maternal uniparental disomy of chromosome 7 patients, and 90 SGA children without SRS. Clinical data were evaluated from patient records, and seven hypomethylated patients were clinically and radiologically reexamined.

RESULTS

H19 ICR hypomethylation was found in 62% of SRS patients but in no SGA children. A clinical severity score demonstrated strong correlation between hypomethylation level and phenotype severity. Hypomethylation related to a more severe SRS phenotype, in which especially asymmetry and micrognathia were significantly more common. Extremely hypomethylated patients had abnormally high lumbar vertebrae, lumbar hypomobility, elbow subluxations, and distinct hand and foot anomalies. They also presented with congenital aplasia of the uterus and upper vagina, equivalent to the Mayer-Rokitansky-Küster-Hauser syndrome in females, and cryptorchidism and testicular agenesis in males.

CONCLUSIONS

We found a dose-response relationship between the degree of H19 hypomethylation and phenotype severity in SRS. We report for the first time the association of specific anomalies of the spine, elbows, hands and feet, and genital defects in SRS with severe H19 hypomethylation. Classical SRS features were found in H19 hypomethylation and milder symptoms in maternal uniparental disomy of chromosome 7, thus distinguishing two separate clinical and etiological subgroups.

Investigating parent of origin effects in studies of type 2 diabetes and obesity

The role of parent-of-origin effects (POE) in the etiology of complex diseases such as type 2 diabetes (T2DM) and obesity is currently of intense interest, but still largely unclear. POE are transmittable genetic effects whereby the expression of the phenotype in the offspring depends upon whether the transmission originated from the mother or father. In mammals, POE can be caused by genetic imprinting, intrauterine effects, or maternally inherited mitochondrial genes. In this paper, we describe the different mechanisms underlying POE, characterize known examples of POE in rare forms of diabetes, and review the evidence from linkage and association studies for POE in T2DM and obesity. Finally, we summarize some of the new and established statistical and experimental approaches commonly used to detect POE. Through this paper, we hope emphasizes the potentially significant importance of POE in the etiology of T2DM and obesity.

Epigenetics in Silver-Russell syndrome

Silver-Russell syndrome (SRS) is a clinically heterogeneous syndrome characterized by intra-uterine and postnatal growth retardation with spared cranial growth, dysmorphic features and frequent body asymmetry. Various cytogenetic abnormalities have been described in a small number of SRS or SRS-like cases involving chromosomes 7, 8, 11, 15, 17 and 18. However, until recent data became available involving imprinted genes on chromosome 7 and chromosome 11p15, the molecular cause of the syndrome was unknown in most cases. Genomic imprinting is the best example of transcriptional control of genes by epigenetic modifications. Many imprinted genes play key roles in fetal and placental growth and behaviour. This is illustrated in SRS, which can now be considered as a new imprinting disease model. These new findings in the pathophysiology of SRS allow long-term follow-up studies to be performed based on molecular diagnosis. This could help to define appropriate clinical guidelines regarding growth and feeding difficulties.

Restriction Site–Specific Methylation Studies of Imprinted Genes with Quantitative Real-Time PCR

Background: Epigenetic studies, such as the measurement of DNA methylation, are important in the investigation of syndromes influenced by imprinted genes. Quick and accurate quantification of methylation at such genes can be of appreciable diagnostic aid.

Methods: We first digested genomic DNA with methylation-sensitive restriction enzymes and used DNA without digestion as a control and nonmethylated λ DNA as an internal control for digestion efficiency. We then performed quantitative real-time PCR analyses with 6 unique PCR assays to investigate 4 imprinting control regions on chromosomes 7 and 11 in individuals with uniparental disomy of chromosome 7 (UPD7) and in control individuals.

Results: Our validation of the method demonstrated both quantitative recovery and low methodologic imprecision. The imprinted loci on chromosome 7 behaved as expected in maternal UPD7 (100% methylation) and paternal UPD7 (<10% methylation). In controls, the mean (SD) for percent methylation at 2 previously well-studied restriction sites were 46% (6%) for both H19 and KCNQ1OT1, a result consistent with the previously observed methylation rate of approximately 50%. The methylation percentages of all investigated imprinted loci were normally distributed, implying that the mean and SD can be used as a reference for screening methylation loss or gain.

Conclusion: The investigated loci are of particular importance for investigating the congenital Silver–Russell and Beckwith–Wiedemann syndromes; however, the method can also be applied to other imprinted regions. This method is easy to set up, has no PCR bias, requires small amounts of DNA, and can easily be applied to large patient populations for screening the loss or gain of methylation.

Third case of paternal isodisomy for chromosome 7 with cystic fibrosis: a new patient presenting with normal growth

Many patients with maternal uniparental disomy of chromosome 7 (UPD7) have been described, mainly with intrauterine and postnatal growth retardation or with Silver-Russell syndrome. In contrast, only three cases of paternal UPD7 have been reported, all associated with recessive disorders. Here, we report on the clinical and molecular data of the third patient with paternal UPD7 and cystic fibrosis. Pre- and postnatal growth were normal. These findings support the hypothesis that paternal isodisomy for human chromosome 7 may have no phenotypic effect on growth.

Growth parameters in maternal uniparental disomy 7 and 14

INTRODUCTION

Growth retardation has been reported in most cases of maternal uniparental disomy (UPD) 7 and 14, but has never been evaluated in a systematic approach. In this study, an analysis is presented of the auxological data from the literature at birth and on the occasion of the last evaluation of 34 cases with maternal UPD 7 (21 heterodisomy, 13 isodisomy) and 29 cases with maternal UPD 14 (22 heterodisomy, 7 isodisomy). For maternal UPD 7, statistical analysis revealed that length and weight at birth as well as on the occasion of the last evaluation were strongly below average (-2.94 SD and -2.62 SD, and -3.39 SD and -3.11 SD, respectively), whereas at both evaluations occipitofrontal head circumference (OFC) was only slightly below the average (-1.00 SD and -0.85 SD). For maternal UPD 14 at birth, growth retardation is rather concordant for length, weight, and OFC (-2.78 SD, -2.84 SD, and -1.69 SD). Later in life body mass index (BMI) is above average (1.06 SD) and continuously increasing before and after puberty (-0.58 SD and 2.07 SD).

CONCLUSION

Growth retardation and relative macrocephaly are of prenatal onset and still present in adults with maternal UPD 7. For patients with maternal UPD 14, growth curves for height, BMI and OFC differ strongly. Genomic imprinting might be a major causative factor, but it seems to function differently for maternal UPD 7 and maternal UPD 14.

Fetal growth restriction and subsequent pregnancy risks

Fetal growth restriction can result from a variety of intrinsic or extrinsic insults, resulting from maternal, fetal, and placental factors. Determining the underlying cause of poor fetal growth can be difficult but is essential for assessing potential risks for future pregnancies. Importantly, recurrence risks greatly depend on these underlying conditions. Understanding these risks can allow more appropriate patient counseling and may influence management strategies to optimize future pregnancies.

Absence of a paternally inherited FOXP2 gene in developmental verbal dyspraxia

Mutations in FOXP2 cause developmental verbal dyspraxia (DVD), but only a few cases have been described. We characterize 13 patients with DVD--5 with hemizygous paternal deletions spanning the FOXP2 gene, 1 with a translocation interrupting FOXP2, and the remaining 7 with maternal uniparental disomy of chromosome 7 (UPD7), who were also given a diagnosis of Silver-Russell Syndrome (SRS). Of these individuals with DVD, all 12 for whom parental DNA was available showed absence of a paternal copy of FOXP2. Five other individuals with deletions of paternally inherited FOXP2 but with incomplete clinical information or phenotypes too complex to properly assess are also described. Four of the patients with DVD also meet criteria for autism spectrum disorder. Individuals with paternal UPD7 or with partial maternal UPD7 or deletion starting downstream of FOXP2 do not have DVD. Using quantitative real-time polymerase chain reaction, we show the maternally inherited FOXP2 to be comparatively underexpressed. Our results indicate that absence of paternal FOXP2 is the cause of DVD in patients with SRS with maternal UPD7. The data also point to a role for differential parent-of-origin expression of FOXP2 in human speech development.

Paternal uniparental isodisomy of the entire chromosome 3 revealed in a person with no apparent phenotypic disorders

Uniparental disomy (UPD) is a rare genetic abnormality. During a whole genome linkage study we identified a case of paternal uniparental isodisomy 3 serendipitously. This is the first ascertained human paternal UPD for chromosome 3 (UPD3pat). The finding of this paternal UPD case of the entire chromosome 3 with no apparent phenotypic disorders suggests that there are no paternal imprinted genes causing rare genetic disorders on chromosome 3.

Diagnostic proceeding in Silver-Russell syndrome

BACKGROUND

Silver-Russell syndrome (SRS) describes a uniform malformation syndrome characterized by pre- and postnatal growth restriction (<3rd percentile) and a typical craniofacial gestalt. The basic defect of SRS is currently unknown, and the number of meaningful genetic tests available is therefore limited. Different chromosomal aberrations have been identified, including in the chromosomal region 7p12-p14. Detailed analyses of numerous candidate genes have not revealed any relevant insights with respect to the etiology of the disease.However, maternal uniparental disomy (UPD) of chromosome 7 (matUPD7), the inheritance of both homologues of chromosome 7 only from the mother, is observed in approximately 10% of SRS patients. Here, we report on our experiences of UPD testing in patients referred to our laboratory with the clinical diagnosis of SRS. A diagnostic algorithm for SRS is suggested.

METHODS

Eighty-six patients with the clinical diagnosis of SRS were screened for matUPD7 by microsatellite typing. In 13 cases, the clinical data were consistent with the diagnosis of SRS. The other 73 patients were referred for UPD testing with the suspected diagnosis of SRS, but clinical data were scarce.

RESULTS

In total, we identified three new cases of matUPD7: one patient belonged to the cohort of 13 clinically characterized patients; the other two patients were referred with the suspected diagnosis of SRS but initially without detailed reports. DNA studies revealed uniparental heterodisomy 7 in two patients, while the results in the third case were consistent with uniparental isodisomy.

CONCLUSIONS

MatUPD7 is predominantly detectable in patients showing SRS features, and testing should therefore be restricted to this group of growth-restricted patients. Generally, a combination of cytogenetic and molecular genetic tests can be offered in SRS, aiming at the detection of chromosomal rearrangements and matUPD7 in >10% of SRS patients.

Cystic fibrosis and Russell-Silver syndrome in a child with maternal isodisomy of chromosome 7

A 6-year-old Asian girl was diagnosed with cystic fibrosis at 3 months of age, following investigations for failure to thrive. She had intrauterine growth retardation and continued to have restricted postnatal growth, despite adequate caloric intake and enzyme replacement therapy. Further investigations were initiated when she was 5 years old, as her growth was not responding to the usual treatment measures. These tests revealed that she had maternal isodisomy of chromosome 7.

Uniparental disomy (UPD) other than 15: Phenotypes and bibliography updated

Uniparental disomy (UPD) describes the inheritance of a pair of chromosomes from only one parent. The concept was introduced in Medical Genetics by Engel (1980); Am J Med Genet 6:137-143. Aside UPD 15, which is the most frequent one, up to now (February 2005) 197 cases with whole chromosome maternal UPD other than 15 (124 X heterodisomy, 59 X isodisomy, and 14 cases without information of the mode of UPD) and 68 cases with whole chromosome paternal UPD other than 15 (13 X heterdisomy, 53 X isodisomy, and 2 cases without information of the mode of UPD) have been reported. In this review we discuss briefly the problems associated with UPD and provide a comprehensive clinical summary with a bibliography for each UPD other than 15 as a guide for genetic counseling.

Silver-Russell syndrome as a cause for early intrauterine growth restriction

The diagnosis of Silver-Russell syndrome is based on the characteristic growth restriction and the presence of typical dysmorphic features. We present the prenatal and postnatal findings of a case that was treated at our perinatal center. The suspected diagnosis Silver-Russell syndrome was confirmed after delivery by our medical genetic and neonatology services. The authors want to point out that SRS should be considered in the differential diagnosis of early asymmetric intrauterine growth restriction.

Genetic Analysis of Short Stature

Short stature is a major concern for patients and their parents, and represents a diagnostic challenge to the clinician. A correct diagnosis is of particular importance in view of the availability of effective, but costly, therapy in a small subset of cases. Many different genetic etiologies of short stature are known. Therefore, chromosome as well as molecular analysis are requisite diagnostic investigations in children with short stature. Particularly in the group of children with idiopathic short stature, possibilities of molecular analysis are often underestimated. Important options are UPD7 and the FGFR3, SHOX, GH1 and GHR genes. Furthermore, analysis of the IGF and IGF1R genes should be considered. We propose a flow chart for molecular analysis in short stature.

Current challenges in cystic fibrosis screening

CONTENT

This article gives an overview of the symptoms and mutations associated with classic and atypical cystic fibrosis (CF). Current testing methods for mutation detection in CF are discussed.

OBJECTIVES

Review testing for CF, including American College of Medical Genetics and American College of Obstetrics and Gynecology guidelines and recommendations regarding population screening for CF. Describe symptomatic and mutational differences between patients with classic CF and atypical CF, including monosymptomatic conditions such as congenital bilateral absence of the vas deferens, idiopathic pancreatitis, and chronic sinusitis. Explain the concern about predicting the phenotypic expression of the condition from the genotype. Discuss the challenges of CF testing, including the preanalytic, analytic, and postanalytic phases. List the current methods for detecting CF transmembrane conductance regulator gene mutations, specifying the advantages and disadvantages of each. Describe the basic patient information necessary for laboratories to provide accurate risk assessments, such as ethnicity and family history, and reasons for the test being conducted (carrier or affected status).

RESULTS

The technical challenges of detecting the 25 recommended mutations are being met by commercially available reagents. Challenges remain for the preanalytic and postanalytic phases. Only with accurate patient information can laboratories provide specific risk reductions on the basis of a negative genetic test result.

CONCLUSION

As health care providers become better informed about the recommendations for CF testing and laboratories continue to increase the sensitivities of their assays, patients will benefit from increased screening efficiency and accuracy. This will allow affected individuals to receive prompt and effective treatment and carriers to enjoy an expanded number of reproductive options.

Myoclonus in a patient with a deletion of the epsilon-sarcoglycan locus on chromosome 7q21

Autosomal dominant myoclonus-dystonia syndrome (MDS) is characterized by myoclonic and/or dystonic movements with onset as early as infancy. In most families, MDS is caused by mutations in the gene SGCE, which encodes epsilon -sarcoglycan and is located on chromosome 7q21. Data from several sources, including multi-generation pedigrees revealing parent-of-origin effects on MDS penetrance, suggest that SGCE is maternally imprinted. We present a 32-month-old patient with an interstitial deletion affecting chromosome 7q21, and a phenotype including myoclonus, microcephaly, short stature, dysmorphic face and language delay. We used fluorescence in situ hybridization (FISH) to estimate the size of our patient's deletion (9.0-15 Mbp) and to confirm absence of SGCE on the affected chromosome. Polymerase chain reaction (PCR) analysis of polymorphic markers in the region revealed that the paternally inherited chromosome contained the deletion, consistent with a model of maternal SGCE imprinting. Our patient is the first case of MDS caused by complete deletion of SGCE, and represents a new contiguous gene disorder. The case underscores the need to consider chromosomal deletions in patients whose phenotypes are more complex than the classic presentation of a known disease.