Association of the missense variant p.Arg203Trp in PACS1 as a cause of intellectual disability and seizures

Graphical abstract key: ADHD, attention deficit hyperactivity disorder; ASD, atrial septal defect; DD, developmental delay; EEG, electroencephalogram; Ht, height; ID, intellectual disability; OCD, obsessive-compulsive disorder; OFC, open fontanelle; PDA, patent ductus arteriosis; PFO, patent foramen ovale; VSD, ventricular septal defect; Wt, weight.

Social cognitive training in adolescents with chromosome 22q11.2 deletion syndrome: feasibility and preliminary effects of the intervention

BACKGROUND

Children with chromosome 22q11.2 deletion syndrome (22q11DS) often have deficits in social cognition and social skills that contribute to poor adaptive functioning. These deficits may be of relevance to the later occurrence of serious psychiatric illnesses such as schizophrenia. Yet, there are no evidence-based interventions to improve social cognitive functioning in children with 22q11DS.

METHODS

Using a customised social cognitive curriculum, we conducted a pilot small-group-based social cognitive training (SCT) programme in 13 adolescents with 22q11DS, relative to a control group of nine age- and gender-matched adolescents with 22q11DS.

RESULTS

We found the SCT programme to be feasible, with high rates of compliance and satisfaction on the part of the participants and their families. Our preliminary analyses indicated that the intervention group showed significant improvements in an overall social cognitive composite index.

CONCLUSIONS

SCT in a small-group format for adolescents with 22q11DS is feasible and results in gains in social cognition. A larger randomised controlled trial would permit assessment of efficacy of this promising novel intervention.

Genetic Counseling for Fragile X Syndrome: Recommendations of the National Society of Genetic Counselors

The National Society of Genetic Counselors' (NSGC) recommendations for fragile X syndrome (FXS) genetic counseling are intended to assist health care professionals who provide genetic counseling for individuals and families in whom the diagnosis of FXS is strongly suspected or has been made. The recommendations are the opinions of genetic counselors with expertise in FXS counseling and are based on clinical experience, a review of pertinent English language medical articles, and reports of expert committees. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Genetic Counseling-Stress, Coping, and the Empowerment Perspective

Historically one of the basic foundations of the genetic counseling process has been nondirectiveness; however, its definition and utility continues to be in question. There remains a need to develop genetic counseling interventions in order to qualify, quantify, measure, and enhance the genetic counseling process as well as to delineate the complex interactions of education and counseling that occur. We propose a framework for genetic counseling interventions utilizing an empowerment perspective and Lazarus and Folkman's adaptation of the theory of stress and coping. This model frames the genetic counseling process as one that promotes the autonomy of the individual by providing the individual with the tools required to make their own decisions and enhances coping and adjustment to the outcome of those decisions through control and mastery.

Practical considerations in the clinical application of whole-exome sequencing

Despite the exciting advent of whole-exome sequencing (WES) in medical genetics practices, the optimal interpretation of results requires further actions such as reconsidering clinical information and obtaining further laboratory testing. There are no published data to guide clinicians in this process. In a retrospective study on 93 patients who underwent clinical WES, we set out to assess and resolve these practical challenges. With the laboratories reporting a molecular diagnostic rate of 25.8%, the medical geneticists and the laboratories were 90% concordant in their interpretation of the WES results. Divergence occurred when the medical geneticist reconsidered clinical information and/or additional information regarding pathogenicity of a variant. Variants of uncertain significance were reported in 86% of patients, with 53.7% needing follow-up, such as additional laboratory tests and genotyping of family members. By layering clinical data (e.g. mode of inheritance and phenotypic fit) on to the laboratory results, we developed clinical categories for the WES results. These categories of definite diagnosis (14/93), likely diagnosis (8/93), possible diagnosis (13/93) and no diagnosis (58/93) could be used to convey results to patients uniformly. Our framework for a clinically informed interpretation of the results enhances the utility of WES within medical genetics practices.

Indicators of anxiety and depression in women with the fragile X premutation: assessment of a clinical sample

BACKGROUND

Current research suggests that depression and anxiety may be common problems in women with the fragile X (FMR1) premutation.

METHODS

To learn more about this in a clinical setting, we asked 33 women with the FMR1 premutation and 20 women without the FMR1 premutation to complete the Brief Carroll Depression Scale (Brief CDS) and the Multidimensional Anxiety Questionnaire (MAQ) and to provide information about mental health medication use. Questionnaire findings were compared between groups and with normative samples. Trinucleotide (CGG) repeat counts were also correlated to checklist findings.

RESULTS

Both women with the FMR1 premutation and the comparison group had high current mental health medication use (33% vs. 35%). Approximately 1/3 of the women from both groups had high Brief CDS Total T-scores (33% vs. 30%). More women with the FMR1 premutation had at least one elevated MAQ Total or sub-scale T-score than the comparison group (39% vs. 10%, P = 0.03). Twenty-one per cent of women with the FMR1 premutation had all three of the indicators of distress targeted in this study vs. none of the women in the comparison samples (P < 0.05). There was no statistically significant correlation between CGG repeat size and abnormal checklist findings using the Spearman rank correlation, although a higher percentage of women with >100 CGG repeats (57%) had an elevated Brief CDS Total T-score than women with <or=100 CGG repeats (16%) (P = 0.02). More women with >100 CGG repeats also had all three indicators of anxiety and depression (P = 0.03).

CONCLUSIONS

Women with the FMR1 premutation appear to have a high incidence of depression and increased symptoms of anxiety. Screening tools like the Brief CDS and the MAQ may be useful to identify these women in the clinic setting. Positive identification could lead to increased mental health care and treatment.

Longitudinal study of the carrier testing process for fragile X syndrome: perceptions and coping

This paper reports the results of a longitudinal study of women at-risk to inherit the fragile X mutation. It addresses 1) how upsetting the women perceived their carrier information to be, 2) how serious a problem they perceive fragile X syndrome to be, and 3) descriptions of feelings about the carrier testing process. The study sample consisted of 42 women (20 carriers and 22 noncarriers). There were two measurement times (just prior to carrier testing and after learning actual carrier status). The measures used were a Fragile X Visual Analog Scale and a structured interview. At time 1, being at-risk was reported to be upsetting and fragile X syndrome was perceived to be a serious problem. For the women found to be carriers there was no change from time 1 to time 2 on any of the items. Significant change occurred in the non-carriers. They were significantly less upset at time 2 after receiving the results of their carrier test than at time 1. They also perceived fragile X syndrome to be a more serious problem than they did at time 1 and a more serious problem than the carriers at time 2. Themes found included concerns that carrier status for fragile X syndrome presented a barrier for having healthy biological children and concern for children's and grandchildren's adaptation to their own carrier status. Coping behaviors were activated to manage the emotions related to these concerns. The coping behaviors identified were minimization, acceptance of the possibility of being a carrier, a sense of being able to deal with the outcome of the carrier test, positive comparison, problem solving, and positive interpretation.

Carrier testing in fragile X syndrome: effect on self-concept

The purpose of the study was to explore self-concept in women at risk for inheriting the fragile X mutation. Time 1 measures were obtained prior to carrier testing and Time 2 measures were collected approximately 5 months after learning carrier status. The sample consisted of 42 women from 17 families. Measures included the Tennessee Self-Concept Scale (TSCS), the fragile X Visual Analog Scale (VAS), and a structured interview. The TSCS provided a global measure of self-concept and the fragile X VAS and structured interview provided a contextual measure of self related to carrier status. Results indicated that there were no differences initially between carriers and noncarriers and no change from Time 1 to Time 2 on the TSCS. Analysis of the Time 1 fragile X VAS means for the total sample found a reduction in positive feelings about self. Analysis of the Time 2 fragile X VAS found that noncarriers reported improvement in feelings about self, with no change in feelings about self found in the carriers. Responses from the structured interview indicated that the feelings regarding self in the context of genetic testing are not related to global self-concept, but result from concerns regarding the implications of a positive carrier test for themselves and their families. This information highlights areas related to carrier testing that warrant further investigation and may ultimately result in modifications to the genetic counseling.

Prenatal diagnosis of glycogen storage disease type IV using PCR-based DNA mutation analysis

Deficiency of glycogen branching enzyme activity causes glycogen storage disease type IV (GSD-IV). Clinically, GSD-IV has variable clinical presentations ranging from a fatal neonatal neuromuscular disease, to a progressive liver cirrhosis form, and to a milder liver disease without progression. Current methods for prenatal and postnatal diagnosis are based on an indirect method of measuring the enzyme activity, which has a limited sensitivity and cannot be used to distinguish patients with these variable clinical phenotypes. In this study, a GSD-IV family with a non-progressive hepatic form of the disease requested prenatal diagnosis. Determination of the branching enzyme activity in cultivated amniocytes showed 20 per cent residual activity overlapping with the level detected in the heterozygotes. Mutation analysis revealed that the fetus carried two mutant alleles, L224P and Y329S, the same as the proband of this family. The fetus was predicted to be affected and postnatally his clinical presentation is consistent with the diagnosis. We conclude that DNA mutation analysis should be used in the prenatal diagnosis of GSD-IV, especially in the situation of high residual enzyme activity.

Parental attitudes regarding carrier testing in children at risk for fragile X syndrome

Sixty-five parents of individuals affected by fragile X syndrome who attended the National Fragile X Conference in Portland, Oregon (1996), were asked to complete a survey assessing parental level of concern about carrier testing in children at risk for fragile X syndrome. All subjects completed a 15-item paper and pencil Likert response scale measure that was developed specifically for this study. The items included parental rights and duties, psychological adjustment, adaptation, discrimination, harm, childbearing, and interpersonal relationships. The major concern of the parents was that their children have knowledge of their carrier status prior to becoming sexually active and that their children be able to marry informed of their genetic risk. Mothers were significantly more concerned than fathers about raising their children with the knowledge of their carrier status. A sense of parental right to make the decision regarding carrier testing for children was associated with concerns about (1) behavioral or educational problems, (2) knowledge of carrier status prior to sexual activity or marriage, and (3) adjustment of the children to knowledge of their carrier status. As the sample was drawn from a unique population of parents, the results of this survey should be interpreted with caution. The findings of this study suggest a model of parents providing anticipatory guidance for their children to help them adjust to carrier information and for their children to have this knowledge prior to the possibility of reproduction.

A gene on chromosome 11q23 coding for a putative glucose- 6-phosphate translocase is mutated in glycogen-storage disease types Ib and Ic

Glycogen-storage diseases type I (GSD type I) are due to a deficiency in glucose-6-phosphatase, an enzymatic system present in the endoplasmic reticulum that plays a crucial role in blood glucose homeostasis. Unlike GSD type Ia, types Ib and Ic are not due to mutations in the phosphohydrolase gene and are clinically characterized by the presence of associated neutropenia and neutrophil dysfunction. Biochemical evidence indicates the presence of a defect in glucose-6-phosphate (GSD type Ib) or inorganic phosphate (Pi) (GSD type Ic) transport in the microsomes. We have recently cloned a cDNA encoding a putative glucose-6-phosphate translocase. We have now localized the corresponding gene on chromosome 11q23, the region where GSD types Ib and Ic have been mapped. Using SSCP analysis and sequencing, we have screened this gene, for mutations in genomic DNA, from patients from 22 different families who have GSD types Ib and Ic. Of 20 mutations found, 11 result in truncated proteins that are probably nonfunctional. Most other mutations result in substitutions of conserved or semiconserved residues. The two most common mutations (Gly339Cys and 1211-1212 delCT) together constitute approximately 40% of the disease alleles. The fact that the same mutations are found in GSD types Ib and Ic could indicate either that Pi and glucose-6-phosphate are transported in microsomes by the same transporter or that the biochemical assays used to differentiate Pi and glucose-6-phosphate transport defects are not reliable.

Prenatal diagnosis and carrier detection for glycogen storage disease type III using polymorphic DNA markers

Deficiency of glycogen debranching enzyme gene (AGL) causes glycogen storage disease type III (GSD-III), an autosomal recessive disease. Prenatal diagnosis and carrier detection using enzymatic methods are technically difficult and have limited ability to distinguish a carrier from an affected patient. Mutations in the AGL gene can be used for these purposes. However, the mutations identified thus far account for less than half of the total mutant alleles, and no common mutations have been detected except in North African Jews and in a rare subtype of the disease (GSD-IIIb). Our recent identification of three highly informative DNA polymorphic markers in the AGL gene allowed us to perform prenatal diagnosis and carrier detection in two GSD-III families with unknown mutations, using the polymerase chain reaction (PCR) and restriction analysis. In one family, a fetus was diagnosed to be a GSD-III carrier and his carrier status was confirmed postnatally. A newborn in the second family was postnatally diagnosed with the disease.

Carrier testing in the fragile X syndrome: attitudes and opinions of obligate carriers

This study surveyed obligate carriers of the fragile X syndrome fra(X) to ascertain opinions and attitudes regarding carrier testing. Female carriers of fra(X) syndrome were recruited during their visits to the Fragile X Clinic at Duke University Medical Center. Twenty-eight obligate carriers completed a 48 question structured interview and a visual analog scale (VAS). Strong trends in the responses were identified. Fra(X) syndrome was viewed as a very serious problem and the risk to offspring high. Subjects reported that prior knowledge of carrier status would have changed their reproductive plans. All felt that relatives should be informed about the inheritance of fra(X) syndrome; the mean age given for preferred age to inform their children of the inheritance of fra(X) syndrome was 12 years, and mean age given for optimal timing of carrier testing was 10 years. The women interviewed indicated that growing up with knowledge of their carrier status would have been preferable to learning this information as adults and they endorsed an aggressive approach to informing and testing their children. Further investigation is warranted to determine the psychological consequences of carrier testing for fra(X) syndrome in order to develop appropriate guidelines for testing and informing individuals at risk for fra(X) syndrome.

A fragile X male with a broad smear on Southern blot analysis representing 100-500 CGG repeats and no methylation at the EagI site of the FMR-1 gene

Fragile X DNA studies were carried out on all obligate carriers of a large fragile X family with 10 mentally retarded individuals. One 64-year-old carrier man with an altered FMR-1 allele was not described as being mentally retarded or as having any limitations in function. He was married, raised 8 children, and worked as an auto mechanic. On examination, he had macrocephaly and mild macroorchidism but few of the other typical physical findings of males with fragile X syndrome. His Full Scale IQ is 73, and his Vineland Adaptive Behavior Composite is 73. On the Woodcock-Johnson Psycho-Educational Battery-Revised, he achieved standard scores of 64 in Reading, 55 in Math, and 83 in Knowledge. His DNA findings showed a broad smear on Southern blot analysis of 100-500 CGG repeats and no methylation at the EagI site upstream of the FMR-1 protein coding region. His FMR-1 protein production is 12% of normal. His daughters all have large premutations, with somatic instability in the size of the CGG repeat lengths. They all have evidence of academic underachievement and 2 have physical characteristics frequently described in individuals with fragile X.

Clinical and laboratory findings in four patients with the non-progressive hepatic form of type IV glycogen storage disease

The classic clinical presentation for type IV glycogen storage disease (branching enzyme deficiency, GSD IV) is hepatosplenomegaly with failure to thrive occurring in the first 18 months of life, followed by progressive liver failure and death by age 5 years. Although there have been two patients without apparent liver progression previously reported, no long-term follow-up clinical data have been available. We present here the clinical spectrum of the non-progressive liver form of GSD IV in four patients, and long-term follow-up of the oldest identified patients (ages 13 and 20 years). None has developed progressive liver cirrhosis, skeletal muscle, cardiac or neurological involvement, and none has been transplanted. Branching enzyme activity was also measured in cultured skin fibroblasts from patients with the classic liver progressive, the early neonatal fatal, and the non-progressive hepatic presentations of GSD IV. The residual branching enzyme activity in the patients without progression was not distinguishable from the other forms and could not be used to predict the clinical course. Our data indicate that GSD IV does not always necessitate hepatic transplantation and that caution should be used when counselling patients regarding the prognosis of GSD IV. Patients should be carefully monitored for evidence of progression before recommending liver transplantation.

Dissemination of genetic risk information to relatives in the fragile X syndrome: guidelines for genetic counselors

Fragile X Syndrome, which affects 1 in 1,250 males, is the most common inherited condition causing mental retardation. Although carrier detection for the fragile X syndrome utilizing DNA has now been simplified, genetic counseling and the process of informing at-risk family members remains complex. The purpose of this paper is to offer practical guidelines to health professionals providing genetic counseling to fragile X families in order to facilitate the dissemination of genetic risk information to relatives. This paper was developed from a workshop held at the 4th International Fragile X Conference. The guidelines presented here represent a beginning in the development of an approach to informing relatives in fragile X families about genetic risk, and the identification of mechanisms to reduce the burden to families.

Fryns syndrome survivors and neurologic outcome

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome characterized by diaphragmatic hernia, unusual facies, and distal limb hypoplasia. It was first reported as a lethal condition. We report on a three-year-old survivor with Fryns syndrome, and provide a review on the outcome of other survivors. Patients who survive the neonatal period represent 14% of reported cases. Characteristics of survivors include less frequent diaphragmatic hernia and milder lung hypoplasia, absence of complex cardiac malformation, and neurologic impairment. Multiple central nervous system abnormalities have been reported in Fryns syndrome, including agenesis of the corpus callosum, Dandy-Walker abnormality, cerebellar heterotopias, cerebellar hypoplasia, enlarged ventricles, and hypoplasia of the olfactory bulbs. Our patient exhibited profound mental retardation. He had malformations of gyration and sulcation, particularly around the central sulcus, and hypoplastic optic tracts beyond the optic chiasm. Understanding of long-term outcome of survivors is important for counseling of families with Fryns syndrome. Careful brain examination is advised; however, a normal radiological brain examination does not preclude developmental delay. The spectrum of individual outcome and of associated anomalies indicates that individual evaluation, including imaging for structural brain malformation, is strongly advised.

Hemangioma, supraumbilical midline raphé, and coarctation of the aorta with a right aortic arch: single causal entity?

Most congenital cutaneous hemangiomas are a sporadic occurrence. Hemangiomas have been found in association with coarctation of the aorta and a right aortic arch. A separate association has been noted of midline ventral defects with hemangiomas. We report on a patient with multiple hemangiomas, coarctation of the aorta and a right aortic arch, a superaumbilical midabdominal raphé and sternal cleft. Our patient represents an overlap between these two conditions. Review of the literature identified four additional patients with a similar combination of anomalies. The clinical overlap between these 5 patients suggests that they are variants of the same conditions and represent a spectrum of defects that includes hemangiomas, midline ventral defects, aortic arch abnormalities and brain malformation.

Genetic basis of glycogen storage disease type 1a: prevalent mutations at the glucose-6-phosphatase locus

Diagnosis of glycogen storage disease (GSD) type 1a currently is established by demonstrating the lack of glucose-6-phosphatase (G6Pase) activity in the patient's biopsied liver specimen. Recent cloning of the G6Pase gene and identification of mutations within the gene that causes GSD type 1a allow for the development of a DNA-based diagnostic method. Using SSCP analysis and DNA sequencing, we characterized the G6Pase gene of 70 unrelated patients with enzymatically confirmed diagnosis of GSD type 1a and detected mutations in all except 17 alleles (88%). Sixteen mutations were uncovered that were shown by expression to abolish or greatly reduce G6Pase activity and that therefore are responsible for the GSD type 1a disorder. R83C and Q347X are the most prevalent mutations found in Caucasians, 130X and R83C are most prevalent in Hispanics, and R83H is most prevalent in Chinese. The Q347X mutation has thus far been identified only in Caucasian patients, and the 130X mutation has been identified only in Hispanic patients. Our results demonstrate that the DNA-based analysis can accurately, rapidly, and noninvasively detect the majority of mutations in GSD type 1a. This DNA-based diagnosis now permits prenatal diagnosis among at-risk patients and serves as a database in screening and counseling patients clinically suspected of having this disease.

Glycogen storage disease type Ia in two littermate Maltese puppies

Glycogen storage disease type Ia (GSD-Ia) (von Gierke's disease) was identified in two 47-day-old littermate Maltese puppies. The puppies were presented for necropsy with a history of failure to thrive, mental depression, and poor body condition. Gross findings included small body size and emaciation (212 and 246 g versus 595 g for normal littermate), severely enlarged pale livers (48 and 61 g), and pale kidneys. Histologically, there was marked diffuse vacuolation of hepatocytes with large amounts of glycogen and small amounts of lipid. Renal tubular epithelium was mildly to moderately vacuolated. Soft tissue mineralization was present in renal tubules and pulmonary alveolar septa. Biochemical analysis showed that levels of glucose-6-phosphatase were markedly reduced in liver (0.3 and 0.4 microM/minute/g tissue versus 4.7 +/- 1.5 microM/minute/g tissue for controls) and kidney (0.45 and 0.4 microM/minute/g tissue versus 4.1 microM/minute/g tissue for controls) and that glycogen content was increased in liver (9.4% and 9.4% versus 1.3% +/- 1.4% for controls). This is the first confirmed report of animals with glycogen storage disease type Ia.

Evidence that methylation of the FMR-I locus is responsible for variable phenotypic expression of the fragile X syndrome

DNA at the FMR-1 locus was analyzed by Southern blot using probe StB12.3 in an unusual fragile X family with six brothers, three of whom are affected with fragile X to varying degrees, two of whom are nonpenetrant carriers, and one of whom is unaffected. Fragile X chromosome studies, detailed physical examinations, and psychological testing were completed on all six. Two of the affected brothers and the two nonpenetrant brothers were found to be methylation mosaics. The three affected males spanned the phenotypic and cognitive spectrum of the fragile X syndrome. A correlation was seen between the degree of methylation and the phenotypic expression identified in the three affected males. The two males initially classified as nonpenetrant were found to have mild phenotypic expression which consisted of minor cognitive deficits and a partial physical phenotype. These two, who were negative on fragile X chromosome studies, were found on DNA analysis to have large broad smears, with approximately 97% of the DNA unmethylated. The results described here indicate that some "nonpenetrant" carrier males may have varying amounts of methylation of the FMR-1 region, which can result in mild expression of the fragile X syndrome. The apparently mild phenotypic and cognitive expression of the fragile X syndrome in the two males, initially classified as nonpenetrant, who are mosaic for hypermethylation of an expansion of the CGG repeat in the premutation range, indicates that expression of the syndrome is not confined to males with large, hypermethylated expansions (full mutation) but has instead a gradient effect with a threshold for the full expression of the phenotype.

Prenatal diagnosis of Sanfilippo syndrome type A by early amniocentesis

Early amniocentesis performed at 13 weeks gestation was utilized to obtain amniocytes for culture. Sonicates of cultured amniocytes were used to measure heparin sulfamidase activity for assessment of the status of an at risk pregnancy for Sanfilippo syndrome, type A. The heparin sulfamidase activity was not detectable in cultured amniocytes of the fetus at risk while another enzyme, N-acetylglucosamine 6-sulfatase, was comparable to that of the control. Following termination of the pregnancy, various tissue from the fetus were used for assay of both enzymes. The sulfamidase activity was not detectable in any of the fetal tissue while the 6-sulfatase activity was present in all fetal tissue but varied in activity depending on the type of tissue. Cultured fetal skin and brain contained the highest enzyme activity while skin and liver contained the lowest.

Medium-chain acyl CoA dehydrogenase deficiency: Its relationship to SIDS and the impact on genetic counseling

Sudden infant death syndrome (SIDS) is defined as the sudden and unexpected death of an apparently healthy infant under 1 year of age. Routine autopsies often provide few clues as to the cause of death and rarely include a biochemical evaluation. Genetic counseling for SIDS can be difficult as recurrence risks vary depending on the age at death and the number of deaths which have occurred in the family. Biochemical disorders may account for up to 5% of SIDS. Of the metabolic disorders known to be involved in SIDS, the most commonly found is medium-chain acyl CoA dehydrogenase deficiency (MCAD). MCAD is an autosomal recessive disorder of fatty acid oxidation which accounts for up to 1% of SIDS. For some families, the addition of a postmortem biochemical investigation can identify an unsuspected metabolic disorder as the cause of death. Once the diagnosis is established, accurate genetic counseling can then be provided. Metabolic testing of the surviving siblings of victims of sudden death, and the subsequent identification of those due to MCAD can prevent the tragedy of recurrent SIDS in some families. In addition, screening the survivors of an acute life threatening event (ALTE) may also prevent a recurrence.

Unbalanced translocation 46,XY,-15,+der(22)t(15;22)(q13;q11)pat: case report and review of the literature

We present a boy with a rare unbalanced translocation 46,XY,-15,+der(22),t(15;22)(q13;q11) pat. Previous reports of similar chromosome findings mention only the Prader-Willi phenotype. At birth, his manifestations included severe hypotonia and lethargy, (typical of deletion of 15pter----q13); hypertelorism, down-slanting small palpebral fissures, preauricular tags, long philtrum (typical of duplication of 22pter----q11); severe laryngotracheomalacia, and proximal implantation of the thumb. In a review of the literature on chromosome abnormalities involving duplication of 22q11 the associated clinical phenotype consists of mild mental retardation, microcephaly, hypotonia, hypertelorism, down-slanting palpebral fissures, a long philtrum, cleft or highly arched palate, and ear abnormalities. Preauricular pits or tags are common. Cardiovascular defects, renal and genital problems and dislocated hips are frequently present. Anal atresia and colobomata are mainly seen in cat-eye syndrome, the phenotype associated with idic 22q11. Our findings indicate that patients with unbalanced t(15;22) can have manifestations of the dup 22q11, in addition to the previously reported Prader-Willi phenotype, even if the duplicated segment is small.

Prenatal diagnosis of Pompe's disease (type II glycogenosis) in chorionic villus biopsy using maltose as a substrate

Uncultured trophoblasts obtained from chorionic villus biopsy during the gestation period of 8-12 weeks were assayed for alpha-glucosidase activity using maltose as the substrate. Only one major form of maltase activity with a pH optimum at 4.0 was demonstrated. Using this method, we performed prenatal diagnosis on three pregnancies at risk for the infantile form of type II glycogen storage disease. Two affected fetuses and one unaffected fetus were predicted and the diagnosis was subsequently confirmed. The maltose assay offered a direct, simple, and sensitive method for prenatal diagnosis of Pompe's disease in the first trimester.

VATER and hydrocephalus: distinct syndrome?

VACTERL association with hydrocephalus is rarely reported, and is thought to be an autosomal recessive uniformly lethal disorder distinct from the VATER association. We have observed 3 patients in a 12-month period with hydrocephalus due to aqueductal stenosis, in addition to vertebral anomalies (3/3), anal anomalies (3/3), cardiac anomalies (3/3), tracheoesophageal fistula (1/3), renal anomalies (3/3), limb anomalies (3/3), single umbilical artery (2/3), hypospadias (1/3), and cryptorchidism (1/2). Chromosomes were normal in all cases. Although one patient died in the neonatal period due to respiratory failure, 2 have survived (30 months and 19 months) with good neurological outcome following early neurosurgical treatment. Although delayed in motor development, both are interactive, social, and continue to make developmental progress. Appropriate surgical treatment, including early ventriculoperitoneal shunting, allowed for the survival of 2 patients with an unexpectedly good outcome. Our experience suggests that the extremely poor prognosis previously ascribed is not universal. We caution against labeling this syndrome as a uniformly lethal, developmentally devastating disorder.

Prenatal diagnosis of metabolic disease

Early detection of metabolic disease affords the possibility of the best possible outcome for affected infants. Prenatal diagnostic capabilities allow for the institution of prenatal therapy, when indicated, and postnatal optimal management. Special formulas, supplemental nutritional therapies, and avoidance of dangerous substrates can be begun in the delivery room, if the affected status of the patient is known. Such therapies are the current mainstay of treatment of inborn errors of metabolism. Earliest possible institution of these therapies allows hope for the best possible outcome for affected infants.

Oncogenic point mutations in the human retinoblastoma gene: their application to genetic counseling

Mutations of the retinoblastoma gene, most of which cannot be detected by conventional Southern blotting, are known to cause both the nonhereditary and hereditary forms of retinoblastoma and have been implicated in the development of other cancers. Nonhereditary retinoblastoma is caused by a somatic mutation. Hereditary retinoblastoma is caused by a germ-cell mutation, most often a new one, and thus there is usually no family history of the disease. Unlike patients with the nonhereditary disease, those with the hereditary form are at risk for additional retinoblastomas, and their progeny are at risk for the tumors. We used a sensitive technique of primer-directed enzymatic amplification, followed by DNA sequence analysis, to identify mutations as small as a single nucleotide change in tumors from seven patients with simplex retinoblastoma (with no family history of the disease). In four patients the mutation involved only the tumor cells, and in three it involved normal somatic cells as well as tumor cells but was not found in either parent; thus, these mutations appeared to be new, germ-cell mutations. In addition, we found point mutations in cells from a bladder carcinoma, a small-cell carcinoma of the lung, and another retinoblastoma. We conclude that the technique that we have described can distinguish hereditary from nonhereditary retinoblastoma and that it is useful in risk estimation and genetic counseling.

Mild cystic fibrosis linked to chromosome 7q22 markers with an uncommon haplotype

Cystic fibrosis is the commonest autosomal recessive genetic disorder among northern Europeans and their descendants. Recently, investigators have mapped the gene for cystic fibrosis to chromosome 7. We report the results of DNA linkage analysis in a consanguineous family with mild cystic fibrosis. The probes used in this study were pmet D. pmet H, XV-2c, KM.19, and pJ3.11. Linkage to the identified cystic fibrosis locus of 7q22 was established with a peak logarithm of the odds (lod) score of 3.00 at a recombination fraction theta =0.00 using the tightly linked marker KM.19. In addition, we found the D haplotype, which is not commonly associated with cystic fibrosis, to be segregating in this family. The D haplotype is composed of the 1.4-kb allele detectable by XV-2c and the 6.6-kb allele detectable by KM.19. The three patients with cystic fibrosis who had consanguineous parents were homozygous DD, were among the least severely affected, and had no pancreatic insufficiency. The five patients with unrelated parents were heterozygous for the D haplotype and the commoner B haplotype, except one patient who was homozygous DD. All affected persons with pancreatic insufficiency had the DB genotype. These DNA linkage studies provide additional evidence for the existence of a cystic fibrosis allele that is associated with mild disease.

Mild cystic fibrosis in a consanguineous family

Cystic fibrosis is an autosomal recessive genetic disorder linked to chromosome 7q in all families studied. Expression of the disease varies, but the genetic basis for clinical heterogeneity is unknown. We describe an extended consanguineous family with pulmonary disease and the sweat gland phenotype of cystic fibrosis. In the members of this family, clinical expression of the disease was mild, as manifested by the absence of severe childhood lung disease and increased longevity with better functional status than that expected for age. The degree of pancreatic exocrine insufficiency varied (4/10), but the older patients had normal pancreatic function. The pedigree suggested the likelihood of common ancestry, and eight of the ten affected persons were clearly related. At least three of the family members with the mildest clinical disease had consanguineous parents and may therefore have been homozygous for a variant cystic fibrosis gene. The mild expression of cystic fibrosis in this family provides evidence for a form of cystic fibrosis that is intrinsically less debilitating than the classic form.

The case of the gray optic disc!

A child with interstitial deletion of chromosome 17, right optic nerve hypoplasia, and impaired speech had bilateral congenital optic disc pigmentation, giving the appearance of gray optic discs. This appearance did not change over a period of two-and-a-half years. Previous cases of gray optic discs in neonates have been notable for 1) absence of visible pigmentation within the optic discs, 2) resolution of the gray discoloration over a period of months, and 3) development of albinotic features in several infants. This suggests that congenital optic disc pigmentation is a rare cause of gray optic discs. Congenital optic disc pigmentation is compatible with good vision.