Pallister-Killian and Fryns syndromes: nosology

Diaphragmatic Hernia as a Prenatal Feature of Glycosylphosphatidylinositol Biosynthesis Defects and the Overlap With Fryns Syndrome - Literature Review

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome, with diaphragmatic defects and secondary lung hypoplasia as cardinal features. Despite it was reported first in 1979, its exact etiology has not been established to date. With this review, we would like to draw attention to the prenatal presentation of multiple congenital anomalies syndromes, resulting from defects in the synthesis of glycosylphosphatidylinositol anchors, to be considered in a prenatal assessment of fetuses with DH and Fryns-like phenotype.

The genetics of common disorders - congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth defect with a high mortality and morbidity. Although numerous chromosomal aberrations and gene mutations have been associated with CDH, the etiology of the diaphragmatic defect is identified in less than 50% of patients. This review discusses the some of the more frequent, recurrent karyotypic abnormalities in which CDH is a feature, including 15q26, 8p23.1 and 4p16.3 deletions and tetrasomy 12p (Pallister-Killian syndrome), together with some of the syndromes in which CDH is a relatively common feature, including Fryns syndrome, Matthew-Wood syndrome, overgrowth syndromes and Donnai-Barrow syndrome. In the era of genomic technologies, our knowledge of the genes and chromosome regions involved in pathogenesis of CDH is likely to advance significantly.

Congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is defined by the presence of an orifice in the diaphragm, more often left and posterolateral that permits the herniation of abdominal contents into the thorax. The lungs are hypoplastic and have abnormal vessels that cause respiratory insufficiency and persistent pulmonary hypertension with high mortality. About one third of cases have cardiovascular malformations and lesser proportions have skeletal, neural, genitourinary, gastrointestinal or other defects. CDH can be a component of Pallister-Killian, Fryns, Ghersoni-Baruch, WAGR, Denys-Drash, Brachman-De Lange, Donnai-Barrow or Wolf-Hirschhorn syndromes. Some chromosomal anomalies involve CDH as well. The incidence is < 5 in 10,000 live-births. The etiology is unknown although clinical, genetic and experimental evidence points to disturbances in the retinoid-signaling pathway during organogenesis. Antenatal diagnosis is often made and this allows prenatal management (open correction of the hernia in the past and reversible fetoscopic tracheal obstruction nowadays) that may be indicated in cases with severe lung hypoplasia and grim prognosis. Treatment after birth requires all the refinements of critical care including extracorporeal membrane oxygenation prior to surgical correction. The best hospital series report 80% survival but it remains around 50% in population-based studies. Chronic respiratory tract disease, neurodevelopmental problems, neurosensorial hearing loss and gastroesophageal reflux are common problems in survivors. Much more research on several aspects of this severe condition is warranted.

Fryns syndrome a presentation of two siblings with congenital diaphragmatic hernia

INTRODUCTION

Congenital diaphragmatic hernia (CDH) is a congenital malformation that has a reported incidence ranging from 2.4 to 4.1 in 10,000 births. Despite advances in neonatal care, a mortality rate of 33% is still reported with isolated CDH, predominantly due to hypoxic respiratory failure secondary to pulmonary hypoplasia. Fryns syndrome is the most common autosomal recessive syndrome associated with CDH, reported in up to 10% of patients with CDH, comprising CDH, pulmonary hypoplasia, craniofacial abnormalities, distal limb hypoplasia and internal malformations.

CASE PRESENTATION

We present two siblings with lethal CDH born within a 30 month period. The clinical course in these two infants is described and the possible mode of inheritance for CDH in this family is reviewed.

CONCLUSION

In spite of lacking many advanced chromosomal evaluations in our institute we recommended for further investigation into isolated and particularly familial cases may lead to the identification of genetic abnormalities detectable with FISH assay, locus-specific DNA probes, or other new techniques. There remains an ongoing need for careful clinical review and blood banking of cases of CDH to allow better insight into the genetic causes of severe fetal anomalies such as CDH.

Iris transillumination defects associated with pallister-killian syndrome

This report describes a new finding of iris transillumination defects in Pallister-Killian syndrome, a rare multi-system disorder resulting from mosaic tetrasomy of the short arm of chromosome 12.

Genome scan, fine-mapping, and candidate gene analysis of non-syndromic cleft lip with or without cleft palate reveals phenotype-specific differences in linkage and association results

OBJECTIVES

Non-syndromic orofacial clefts, i.e. cleft lip (CL) and cleft palate (CP), are among the most common birth defects. The goal of this study was to identify genomic regions and genes for CL with or without CP (CL/P).

METHODS

We performed linkage analyses of a 10 cM genome scan in 820 multiplex CL/P families (6,565 individuals). Significant linkage results were followed by association analyses of 1,476 SNPs in candidate genes and regions, utilizing a weighted false discovery rate (wFDR) approach to control for multiple testing and incorporate the genome scan results.

RESULTS

Significant (multipoint HLOD >or=3.2) or genome-wide-significant (HLOD >or=4.02) linkage results were found for regions 1q32, 2p13, 3q27-28, 9q21, 12p11, 14q21-24 and 16q24. SNPs in IRF6 (1q32) and in or near FOXE1 (9q21) reached formal genome-wide wFDR-adjusted significance. Further, results were phenotype dependent in that the IRF6 region results were most significant for families in which affected individuals have CL alone, and the FOXE1 region results were most significant in families in which some or all of the affected individuals have CL with CP.

CONCLUSIONS

These results highlight the importance of careful phenotypic delineation in large samples of families for genetic analyses of complex, heterogeneous traits such as CL/P.

Pallister-Killian syndrome: a report of 2 cases and review of its surgical aspects

Pallister-Killian syndrome (PKS) is a rare mosaic genetic disorder defined by the presence of isochromosome for the short arm of chromosome 12. The authors report 2 new cases of PKS with prenatal diagnosis of tetrasomy 12p made by cytogenetic study of amniocytes. Typical dysmorphic craniofacial features were noted postnatally. Both newborns were referred to a surgical department because of congenital anomalies requiring operative management. One had an imperforate anus with an anocutaneous fistula and underwent minor anorectoplasty on day 2 of life. The second newborn required emergency laparotomy because of malrotation with midgut volvulus. This is the first report of clinical manifestation of malrotation in a patient with PKS. The authors undertook a detailed review of reported to date cases of PKS with special emphasis on its surgical aspects.

Single gene disorders associated with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth defect with a high pre- and postnatal mortality. Although the majority of diaphragmatic hernias occur as isolated malformations, additional major and minor anomalies are common and are present in more than 40% of patients. There are compelling data for the importance of genetic factors in the etiology of CDH, but the pathogenesis and the causative genes for CDH in humans remain elusive. There are more than 70 syndromes in which diaphragmatic hernias have been described, and several of these syndromes are single gene disorders for which the gene is known. One method for identifying the causative genes in isolated CDH is to study syndromes with known genes in which CDH is a recognized feature, with the rationale that those genes have a role in diaphragm development. This review discusses the syndromes that are most commonly associated with CDH, with greater attention towards syndromes in which the causative genes have been identified, including Simpson-Golabi-Behmel syndrome, Denys-Drash syndrome, spondylocostal dysostosis, craniofrontonasal syndrome, Cornelia de Lange syndrome and Marfan syndrome.

Overview of epidemiology, genetics, birth defects, and chromosome abnormalities associated with CDH

Congenital diaphragmatic hernia (CDH) is a common and well-studied birth defect. The etiology of most cases remains unknown but increasing evidence points to genetic causation. The data supporting genetic etiologies which are detailed below include the association of CDH with recurring chromosome abnormalities, the existence of CDH-multiplex families, and the co-occurrence of CDH with additional congenital malformations.

Prenatal diagnosis of congenital diaphragmatic hernia in a fetus with 46,XY/46,X,-Y,+der(Y)t(Y;1)(q12;q12) mosaicism: a case report

Congenital diaphragmatic hernia (CDH) is often associated with major anomalies and chromosomal abnormalities. Chromosomal abnormalities are usually detected in 9.5% to 34% of fetuses with CDH prenatally diagnosed and the defect has also been reported in association with multiple syndromes such as Pallister-Killian syndrome, Fryns syndrome, Di George syndrome and Apert syndrome. Among the chromosomal abnormalities associated with CDH, trisomy 21, 18, and 13 are most common. Association with complex chromosomal aberrations such as mosaicism has also been reported. However, CDH presented in a fetus with Y-autosome translocation is extremely rare. Herein, we reported a case of fetus with 46,XY/46,X,-Y, +der(Y)t(Y;1)(q12;q12) mosaicism who presented with CDH diagnosed by ultrasonography at 19 weeks' gestation.

A case of Fryns syndrome without diaphragmatic hernia and review of the literature

We report on a child with Fryns syndrome who showed a characteristic coarse hirsute facial appearance, bilateral cleft lip and palate, cardiac and renal anomalies, dilated bowel and distal limb abnormalities. However, diaphragmatic hernia, which is considered a cardinal feature in this condition, was absent in our patient. The parents were consanguineous supporting autosomal recessive inheritance.

Fryns syndrome: A review of the phenotype and diagnostic guidelines

Fryns syndrome (FS) is the commonest autosomal recessive syndrome associated with congenital diaphragmatic hernia (CDH) and comprises CDH, pulmonary hypoplasia, craniofacial anomalies, distal limb hypoplasia, and internal malformations. Although there have been more than 50 case reports on probands with FS, the diagnostic guidelines were formulated from a review of eight patients and modifications to the guidelines have only once been suggested. Recently, several case reports have described new anomalies in FS and other papers have highlighted the variation in expressivity found in FS. This paper examines the medical literature on FS to define the phenotype and to review the diagnostic guidelines. We conclude that CDH with brachytelephalangy and/or nail hypoplasia is strongly suggestive of the diagnosis and that pulmonary hypoplasia, craniofacial dysmorphism, orofacial clefting, and polyhydramnios are sufficiently frequent to be diagnostically useful. Other distinctive malformations that are consistent with FS include ventricular dilatation or hydrocephalus, agenesis of the corpus callosum, neuronal or cerebellar heterotopias, abnormalities of the aorta, renal cysts, dilatation of the ureters, bicornuate uterus, renal dysplasia, proximal thumbs, and broad clavicles.

A newborn infant with left diaphragm agenesis, radial aplasia and preauricular appendices

We report the case of a baby girl born to consanguineous parents who died 36 hours after birth. She had multiple preauricular appendices, right radial aplasia, triphalangeal thumb and several other anomalies. Differential diagnosis included Fryns syndrome, Pallister-Killian syndrome, and hemifacial microsomia. However, since our patient had congenital diaphragmatic hernia, a rare finding in hemifacial microsomia we suggest that she had a variant form of hemifacial microsomia or an undescribed new syndrome.

Cleft-palate lateral synechia syndrome: insight into the phenotypic spectrum of Fryns syndrome?

BACKGROUND

In 1972, Fuhrmann et al. (Humangenetik 1972;14:196-203) described a novel syndrome consisting of cleft palate (CP) and lateral synechiae (LS) between the palate and the floor of the mouth. This constellation of malformations, since denoted as cleft-palate lateral synechiae syndrome (CPLS), is a rare syndrome; only five cases have been reported since the original description. Because of the paucity of recognized cases, little is known regarding the phenotypic spectrum of this presumably autosomal dominant condition.

CASES

We report two unrelated patients who presented with remarkably similar phenotypic features, including multiple intraoral synechiae (filiforme intraalveolar bands), cleft palate, micrognathia, and redundant lower lip tissue. Their phenotypic findings indicate a diagnosis of CPLS; however, case 3 (the monozygotic twin of case 2) had classic phenotypic features of Fryns syndrome.

CONCLUSIONS

This report presents two new cases of CPLS, and suggests that the CPLS phenotype may represent the mild end of the Fryns syndrome phenotypic spectrum. Supplementary material for this article can be found on the Birth Defects Research (Part A) website (http://www.interscience.wiley.com/ jpages/1542-0752/suppmat/67/fig5.xls).

Documentation of anomalies not previously described in Fryns syndrome

We report on a case of Fryns syndrome with microcephaly, multiple facial anomalies, hypoplasia of distal phalanges, diaphragmatic defect with a thin, translucent diaphragm, microphthalmia (right), anophthalmia (left), and multiple midline developmental defects including gastroschisis, central nervous system defects including left arrhinencephaly and cerebellar hypoplasia, midline cleft of the upper lip, alveolar ridge and maxillary bone, and cleft nose with bilateral choanal atresia. These defects add to our knowledge of the phenotype of Fryns syndrome.

Tissue-limited mosaicism in Pallister-Killian syndrome -- a case in point

We report a case of Pallister-Killian syndrome in a term female infant. Antenatal ultrasound showed left diaphragmatic hernia and polyhydramnios. She was ventilated from birth and the diaphragm defect repaired on day 5. She had dysmorphic features, including median cleft palate, patchy frontotemporal alopecia, hypopigmented skin whorls, and bilateral profound sensorineural hearing loss. Fetal and postnatal karyotypes of peripheral lymphocytes were both normal, 46, XX. Subsequently, a skin fibroblast culture showed mosaic tetrasomy of isochromosome 12p both on G-banding and fluorescence in situ hybridization, consistent with Pallister-Killian syndrome. This case illustrates the importance of using the appropriate sample type for karyotype analysis with implications for prenatal and postnatal diagnosis.

Pallister-Killian syndrome: difficulties of prenatal diagnosis

The first prenatal diagnosis of Pallister-Killian syndrome (PKS) was reported by Gilgenkrantz et al. in1985. Since this report, about 60 prenatal cases have been reported but both sonographic and cytogenetic diagnoses remain difficult. Although ultrasound anomalies such as congenital diaphragmatic hernia, polyhydramnios and rhizomelic micromelia in association with fetal overgrowth are very suggestive of the syndrome, they are inconstant and they may even be absent. The mosaic distribution of the supernumerary isochromosome 12p greatly increases these difficulties. No prenatal cytogenetic technique is sensitive enough to ensure prenatal diagnosis and false-negative results have been described on fetal blood, chorionic villi and amniocentesis. We report here two prenatal cases of PKS which illustrate the great variability of the fetal phenotype. In reviewing the 63 reported cases, we attempt to determine ultrasound indicators of the syndrome and to define a cytogenetic strategy. In cases where ultrasound indicators are present, our proposal is first to perform chorionic villus or placental sampling and then amniocentesis when the first cytogenetic result is normal. Fetal blood sampling is the least indicated method because of the low frequency of the isochromosome in lymphocytes. In this cytogenetic strategy, fluorescent in situ hybridization (FISH) and especially interphase FISH on non-cultured cells increases the probability or identifying the isochromosome. A misdiagnosis remains possible when ultrasound is not contributory; the identification of new discriminating ultrasound indicators would be very helpful in this context.

Fryns syndrome: a surviving case with associated Hirschsprung's disease and hemidiaphragmatic agenesis

Fryns syndrome is a rare autosomal recessive disorder of multiple congenital abnormalities. Major diagnostic criteria include congenital diaphragmatic hernia, distal limb and nail hypoplasia and abnormal facies. More than 70 cases have been reported since the first report in 1979, 86% of which have been associated with an early lethal outcome. We report the case of a survivor who also has associated Hirschsprung's disease. On review of previously reported cases, defects of neuronal migration may be more common than previously recognized. The diaphragmatic hernia was repaired in two stages with a silastic patch followed by a reversed latissimus dorsi muscle flap.

Variability in the phenotypic expression of fryns syndrome: A report of two sibships

We report on two sibships with four fetuses of 12, 15, 17, and 20 weeks of gestation, respectively, and 1 preterm baby of 31 weeks of gestation affected by a multiple congenital disorder with manifestation suggestive of Fryns syndrome. In addition to the characteristic malformation pattern in Fryns syndrome, they presented with fetal hydrops, cystic hygroma, and multiple pterygias, allowing prenatal ultrasound diagnosis as early as in the 11th week of gestation. The two affected fetuses of family 1 showed severe craniofacial anomalies with bilateral cleft lip and palate, acral hypoplasia, postaxial oligodactyly, persistent truncus arteriosus, and interrupted aortic arch, asplenia sequence, and complex central nervous system midline malformations. In family 2 with three affected sibs, ear anomalies with atresia of the auditory canals, postaxial hexadactyly, intestinal atresias, callosal defects, and eye colobomas were the most outstanding features. On the basis of the present findings and former reports, the inter- and intrafamiliar phenotypic variability in Fryns syndrome, possible pathogenetic mechanisms, and the value of prenatal diagnosis are discussed. In the pathogenetic discussion, a special emphasis is put on the neural crest cell developmental field.

Congenital diaphragmatic herniation: antenatal detection and outcome

201 fetuses and babies with a congenital diaphragmatic herniation or eventration (referred to collectively as CDH) were notified to the Northern Region Congenital Abnormality Survey (NorCAS) in the 13-year period from 1985 to 1997, an incidence of 0.25 per 1000 births. The 1-year survival of all pregnancies associated with CDH was 37%. The 1-year survival of livebirths was 50%. Antenatal scan detected the diaphragmatic defect or associated structural abnormality in 50%. Another major structural abnormality was present in 62 (31%); one of these babies survived and 26 pregnancies were terminated. This group contained four of the six antepartum stillbirths, all three intrapartum stillbirths and four of the five spontaneous miscarriages. Non-isolated CDH occurred in association with Fryns (5), Goldenhar (1) and de Lange (1) syndromes, and in 16 of 17 with a chromosome anomaly. 53% of the 139 fetuses with isolated CDH survived to 1 year of age, and 59% of the 124 liveborn survived. Of 37 fetuses with isolated CDH detected before 25 weeks gestation, 12 pregnancies were terminated. There were 11 survivors among the 25 continuing pregnancies (44%). The overall survival of babies with CDH is very poor but, when a defect is identified by ultrasound before 25 weeks gestation, chromosome analysis and a careful ultrasound scan may suggest which fetuses have an isolated diaphragmatic abnormality and a greater chance of survival.

Report of two new cases of Pallister-Killian syndrome confirmed by FISH: tissue-specific mosaicism and loss of i(12p) by in vitro selection

Tissue-specific mosaic distribution of an additional isochromosome 12p is the characteristic chromosomal aberration in Pallister-Killian syndrome. Often it is confined to fibroblasts, whereas lymphocytes show a normal karyotype. Two cases are reported in which the distribution of the additional i(12p) was analysed in various tissues. The isochromosomes were characterised by conventional banding technics and fluorescence in situ hybridization (FISH). In the first case, diagnosed prenatally, 4 different tissues were analysed. A direct preparation of chorionic villi (21 gestational weeks) showed an extra marker chromosome in 19% and two additional copies in 3% of the examined cells. In two cultures of amniocytes (17 and 21 weeks), the i(12p) was observed in 23% and 12%, respectively. It was absent in cultured lymphocytes of fetal blood (21 weeks). The fibroblast long-term culture of umbilical cord showed the i(12p) in 100% of metaphases. In the second case of a term infant the i(12p) was diagnosed in cultured lymphocytes (4%) and fibroblasts (93%). Secondary loss of the isochromosome was evaluated by in vitro selection in case 2 analysing metaphases and interphases of fibroblasts in the 1st, 4th and 5th subculture using FISH. The proportion of cells with i(12p) decreased from 93% to 40% and to 28%, respectively. DNA analysis in case 1 showed a maternal meiotic origin of the i(12p). The prenatally detected clinical findings in both cases showed characteristic abnormalities of the Pallister-Killian syndrome.

Congenital pulmonary lymphangiectasia and other anomalies in a child: provisionally unique syndrome?

Congenital pulmonary lymphangiectasis is a rare anomaly that is causally heterogeneous. It can occur as either an isolated finding or one manifestation of several multiple congenital anomaly syndromes. We describe a child with congenital pulmonary lymphangiectasis and the anomalies who likely has a provisionally unique condition.

Pallister-Killian syndrome: a mild case diagnosed by fluorescence in situ hybridization. Review of the literature and expansion of the phenotype

Pallister-Killian syndrome (PKS) is a rare disorder characterized by a specific combination of anomalies, mental retardation and mosaic presence of a supernumerary isochromosome 12p which is tissue-limited. We report an atypical case of PKS with a mild phenotype. Flourescence in situ hybridization (FISH) was used to demonstrate that the supernumerary marker chromosome identified in the patient's fibroblasts was an isochromosome 12p. This study broadens the spectrum of PKS phenotype. It also illustrates the usefulness of fluorescence in situ hybridization in diagnosis of patients with chromosomal abnormalities and mild or atypical clinical findings.

Fryns syndrome phenotype and trisomy 22

Trisomy 22 was detected in a 32-week-old fetus born to an overweight mother with hypertension. Severe intrauterine growth retardation was associated with phenotypic manifestations of Fryns syndrome: diaphragmatic hernia, facial defects, and nail hypoplasia with short distal fifth phalanges. This is the second report of congenital diaphragmatic hernia in trisomy 22. This case demonstrates the importance of karyotyping malformed fetuses or newborns, even if a nonchromosome syndrome seems identifiable on clinical grounds. To date, at least 10 cases of Fryns syndrome have been reported without chromosome analysis.

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.

Fryns syndrome: two further cases without lateral diaphragmatic defects

We report on two unrelated infants with Fryns syndrome but without lateral diaphragmatic defects. In case 1, a female stillborn, pertinent findings included a coarse facies, cleft palate, short neck with a broad pterygium, heart defect, lung hypoplasia, omphalocele, urogenital malformations, anal atresia, and distal digital hypoplasia. Case 2 showed a coarse facies with cleft lip and palate, para-oesophageal hernia with herniation of the stomach into the thoracic cavity, malrotation of the intestine, hydronephrosis, and anal atresia. At age 14 months she was developmentally severely retarded. These observations represent the 11th and 12th reports of probable Fryns syndrome without lateral diaphragmatic defect.

Skeletal manifestations in Fryns syndrome

We report on a female baby with Fryns syndrome who died soon after birth. The patient had short limbs, coarse face, hypoplastic lungs, diaphragmatic hernia, and acral hypoplasia. Literature review disclosed varying degrees of skeletal manifestations in Fryns syndrome; short limbs may be a component of Fryns syndrome.

Lethal Pallister-Killian syndrome: phenotypic similarity with Fryns syndrome

The Pallister-Killian syndrome is a sporadic multiple congenital anomaly syndrome characterized by "coarse" face, profound mental retardation, and epilepsy. Chromosomes of peripheral lymphocytes are usually normal, but tissue cultures show varying degrees of mosaicism for isochromosome 12p. In babies who die neonatally of severe malformations, including diaphragmatic hernia, and who also have a "coarse" face, acral hypoplasia, and other internal anomalies, Fryns syndrome is more likely to be suspected than Pallister-Killian syndrome, especially if karyotyping is unavailable or if peripheral lymphocytes have a normal chromosome constitution. An initial diagnosis of Fryns syndrome had to be modified in 3 successive newborn infants since chromosome analysis or in situ hybridization with a chromosome 12 probe on kidney tissue demonstrated the mosaic aneuploidy characteristic of Pallister-Killian syndrome. These 3 patients confirm that a similar pattern of malformations can be present in both conditions at birth. It consists of "coarse" face, acral hypoplasia, diaphragmatic hernia, and other defects. Newborn infants who present this phenotype, but lack a conclusively normal chromosome test, may not have Fryns syndrome. A diagnosis of Fryns syndrome should be made carefully to avoid the risk of inappropriate genetic counseling.