Whole-exome sequencing is a valuable diagnostic tool for inherited peripheral neuropathies: Outcomes from a cohort of 50 families.

The inherited peripheral neuropathies (IPNs) are characterized by marked clinical and genetic heterogeneity and include relatively frequent presentations such as Charcot-Marie-Tooth disease and hereditary motor neuropathy, as well as more rare conditions where peripheral neuropathy is associated with additional features. There are over 250 genes known to cause IPN-related disorders but it is estimated that in approximately 50% of affected individuals a molecular diagnosis is not achieved. In this study, we examine the diagnostic utility of whole-exome sequencing (WES) in a cohort of 50 families with 1 or more affected individuals with a molecularly undiagnosed IPN with or without additional features. Pathogenic or likely pathogenic variants in genes known to cause IPN were identified in 24% (12/50) of the families. A further 22% (11/50) of families carried sequence variants in IPN genes in which the significance remains unclear. An additional 12% (6/50) of families had variants in novel IPN candidate genes, 3 of which have been published thus far as novel discoveries (KIF1A, TBCK, and MCM3AP). This study highlights the use of WES in the molecular diagnostic approach of highly heterogeneous disorders, such as IPNs, places it in context of other published neuropathy cohorts, while further highlighting associated benefits for discovery.

Clinical reappraisal of SHORT syndrome with PIK3R1 mutations: toward recommendation for molecular testing and management.

SHORT syndrome has historically been defined by its acronym: short stature (S), hyperextensibility of joints and/or inguinal hernia (H), ocular depression (O), Rieger abnormality (R) and teething delay (T). More recently several research groups have identified PIK3R1 mutations as responsible for SHORT syndrome. Knowledge of the molecular etiology of SHORT syndrome has permitted a reassessment of the clinical phenotype. The detailed phenotypes of 32 individuals with SHORT syndrome and PIK3R1 mutation, including eight newly ascertained individuals, were studied to fully define the syndrome and the indications for PIK3R1 testing. The major features described in the SHORT acronym were not universally seen and only half (52%) had four or more of the classic features. The commonly observed clinical features of SHORT syndrome seen in the cohort included intrauterine growth restriction (IUGR) <10th percentile, postnatal growth restriction, lipoatrophy and the characteristic facial gestalt. Anterior chamber defects and insulin resistance or diabetes were also observed but were not as prevalent. The less specific, or minor features of SHORT syndrome include teething delay, thin wrinkled skin, speech delay, sensorineural deafness, hyperextensibility of joints and inguinal hernia. Given the high risk of diabetes mellitus, regular monitoring of glucose metabolism is warranted. An echocardiogram, ophthalmological and hearing assessments are also recommended.

Tenascin-X deficiency is associated with Ehlers-Danlos syndrome.

The tenascins are a family of large extracellular matrix proteins with at least three members: tenascin-X (TNX), tenascin-C (TNC, or cytotactin) and tenascin-R (TN-R, or restrictin). Although the tenascins have been implicated in a number of important cellular processes, no function has been clearly established for any tenascin. We describe a new contiguous-gene syndrome, involving the CYP21B and TNX genes, that results in 21-hydroxylase deficiency and a connective-tissue disorder consisting of skin and joint hyperextensibility, vascular fragility and poor wound healing. The connective tissue findings are typical of the Ehlers-Danlos syndrome (EDS). The abundant expression of TNX in connective tissues is consistent with a role in EDS, and our patient's skin fibroblasts do not synthesize TNX protein in vitro or in vivo. His paternal allele carries a novel deletion arising from recombination between TNX and its partial duplicate gene, XA, which precludes TNX synthesis. Absence of TNX mRNA and protein in the proband, mapping of the TNX gene and HLA typing of this family suggest recessive inheritance of TNX deficiency and connective-tissue disease. Although the precise role of TNX in the pathogenesis of EDS is uncertain, this patient's findings suggest a unique and essential role for TNX in connective-tissue structure and function.

Lethal acantholytic epidermolysis bullosa due to a novel homozygous deletion in DSP: expanding the phenotype and implications for desmoplakin function in skin and heart.

Desmoplakin is the major linker in desmosomes in epithelia and myocardium, anchoring intermediate filaments by the C-terminus to plakoglobin and plakophilin in the desmosomal plaque. Mutations in the gene DSP encoding desmoplakin have been associated with various phenotypes affecting skin and/or heart. One of these phenotypes, lethal acantholytic epidermolysis bullosa (LAEB), is characterized by extensive postnatal shedding of epidermis leading to early demise and is caused by recessive mutations in the gene DSP resulting in truncation of the desmoplakin C-terminus. Here we describe two infants born to the same consanguinous parents who suffered extensive epidermal dislodgment and died shortly after birth. In addition, universal alopecia, anonychia, malformed ears and cardiomyopathy were observed. As the clinical diagnosis was LAEB, DSP mutation analysis was performed. A homozygous deletion (c.2874del5) abrogating the donor splice site of exon 20 was found. The deletion is predicted to cause read-through in intron 20 with subsequent recognition of a premature termination codon, resulting in desmoplakin lacking its rod domain and C-terminus (p.Lys959MetfsX5). Electron microscopic analysis of skin biopsies showed absence of the desmosomal inner dense plaque and lack of tonofilament insertion. This is the second report of LAEB. These findings suggest DSP mutations as the aetiology of LAEB and cardiomyopathy as part of the phenotype. Furthermore, they indicate that in addition to the desmoplakin C-terminus, the rod domain is dispensable for intrauterine development but is essential for the inner dense plaque of desmosomes.

Familial cases of gastroschisis in a population-based registry.

Only a few familial cases of gastroschisis have been reported. Consequently, the risk of a recurrence has been thought to be very small. In a population-based study of gastroschisis that included an extended pedigree of all probands, 6 (4.7%) out of 127 families had more than one affected relative. The relationships of the affected were: sib, half-sib (2), first cousin, second cousin once removed, and great uncle. Sib recurrence was 3.5%. Our results suggest that pregnancies occurring in a family with a history of gastroschisis may be at higher risk of recurrence than previously thought.

Possible association between the hernia of Morgagni and trisomy 21.

Of the 5 liveborn infants with the hernia of Morgagni recorded in the California Birth Defects Monitoring Program, 3 had trisomy 21. This significant association (P < 10(-6)) between the hernia of Morgagni and trisomy 21 may reflect defective dorsoventral migration of rhabdomyoblasts from the paraxial myotomes, caused by increased cellular adhesiveness in trisomy 21.

Is there an association of Down syndrome and omphalocele?

The possible association of Down syndrome (DS) with omphalocele is controversial. We reviewed the 2,979 live births and stillbirths with DS born from 1983 to 1993 in the catchment area of the California Birth Defects Monitoring Program (CBDMP). We observed one infant with both defects, a number that did not differ significantly from what was expected (P < 0.40). We also reviewed the pathological reports of one of us (L.H.H.) from a series of 36 DS fetuses and neonatal deaths; none had an omphalocele. We then reviewed the literature for epidemiological studies of DS and for epidemiological, surgical, prenatal, and familial studies of omphalocele. Possible biases inherent in each type of study were evaluated. The majority of epidemiological studies showed no association of DS with omphalocele. In surgical series, the occasional infant with both defects was more likely to undergo surgery than infants with omphalocele and trisomies 13 and 18 or other severe birth defects. Inclusion of both omphalocele and umbilical hernia in the same ICD-9 code may explain some of the correlations with DS noticed in a few epidemiological studies. In conclusion, our data suggest that trisomy 21 does not predispose the fetus to an increased risk for an omphalocele.

Ritscher-Schinzel (3C) syndrome: documentation of the phenotype.

Ritscher-Schinzel syndrome or 3C (craniocerebello-cardiac) syndrome is characterized by cardiac defects, cerebellar vermis hypoplasia, and cranial defects. Nineteen cases were reported previously; however, the full spectrum of this disorder has not been determined. We have evaluated two unrelated males with this condition. Both had defects of the endocardial cushion and vermis hypoplasia with hypotonia. In addition, both had hypospadias, a previously undescribed finding of this disorders. Review of the previously reported cases and those described herein demonstrate: 1) Although varying degrees of vermis hypoplasia are accompanied by hypotonia, delayed gross motor function improves with advancing age leaving speech delay as the major neurodevelopmental handicap. 2) Two different types of cardiac anomalies occur: defects of the endocardial cushion ranging from anomalies of the mitral or tricuspid valves to complete AV canal, and/or conotruncal defects. 3) Postnatal growth deficiency was seen in most patients in whom longitudinal information was available. In our review of patients with vermis hypoplasia we ascertained a patient diagnosed as having "Joubert syndrome" who had most findings of the Ritscher-Schinzel syndrome and several other patients with "Dandy-Walker syndrome" who likely have had Ritscher-Schinzel syndrome, suggesting that Ritscher-Schinzel syndrome is more common than has been appreciated. Careful search for the subtle facial changes characteristic of this disorder as well as coloboma, cleft palate/bifid uvula, short neck, syndactyly, and hypoplasia of the nails is warranted when evaluating children with Dandy-Walker malformation with or without clinical signs of Joubert syndrome.

Prenatal diagnosis of the Beckwith-Wiedemann syndrome.

We report on the prenatal diagnosis of Beckwith-Wiedemann syndrome (BWS) in a pregnancy monitored because of a previously affected child. The proposita had classical stigmata of BWS including macroglossia, omphalocele, and typical ear creases. Chromosomes were 46,XX. Both parents and the extended maternal family were clinically normal. In a subsequent pregnancy by another father, the mother had serial ultrasound monitoring at 13.5, 18, and 19 weeks gestation which showed an enlarged abdominal circumference and a 2-cm omphalocele. At termination the female fetus weighed more than two times the expected weight, had striking hypertrophy of skeletal muscles, a protuberant abdomen, and a 2-cm omphalocele and characteristic facial appearance. Autopsy confirmed generalized organomegaly. This is the first report of the prenatal diagnosis of BWS prior to 20 weeks in an at-risk family. The recurrence in this family emphasizes the difficulty in providing accurate genetic recurrence risks in BWS and suggests that ultrasonographic prenatal diagnosis should be offered to families even when the case appears to be "sporadic."

The fetal valproate syndrome.

We evaluated seven children who had been exposed to sodium valproate (or valproic acid) in utero. A consistent facial phenotype was observed in all seven in addition to other birth defects in four. The facial changes consisted of epicanthal folds which continued inferiorly and laterally to form a crease or groove just under the orbit, flat nasal bridge, small upturned nose, long upper lip with a relatively shallow philtrum, a thin upper vermillion border, and downturned angles of the mouth. Hypospadias, strabismus, and psychomotor delay were found in two males; two children had nystagmus and two had low birth weight.

The Potter sequence: a clinical analysis of 80 cases.

Eighty cases of Potter sequence due to a renal or urologic abnormality were studied retrospectively. The abnormal renal findings were bilateral renal agenesis in 21.25%; cystic dysplasia in 47.5%; obstructive uropathy in 25%; and others in 5.25%. Fifteen patients had multiple congenital anomalies; of these three had aneuploidy, four had autosomal recessive syndromes, and eight were of unknown cause. Results of chromosome analysis in 41 patients and 21 sets of parents were abnormal in three patients, one of whom had a balanced translocation carrier parent; two additional patients and three parents had apparently balanced translocations. There was one recurrence within the study (the first child had bilateral renal agenesis and the second cystic dysplasia). The ultrasound prenatal diagnosis of the renal abnormality was made in eight cases between 18 and 34 weeks. Family histories were suggestive of an autosomal dominant gene disorder with incomplete penetrance in four of 45 families with nonsyndromic bilateral renal agenesis and cystic dysplasia. The evaluation of patients with the Potter sequence should include an examination for nonrenal defects, autopsy, chromosome analysis, and renal ultrasound or urologic evaluation of parents. Ultrasonographic prenatal monitoring of subsequent pregnancies in such families is strongly warranted because of a definite but unknown degree of recurrence risk.

Congenital diaphragmatic hernia in the Brachmann-de Lange syndrome.

We present 12 children with typical Brachmann-de Lange syndrome and congenital diaphragmatic hernia. Affected children were more likely to be of low birth weight and to have major upper limb malformations. Hernia repair was attempted in 4 of these children, and only one survived past 12 months. Newborn infants with congenital diaphragmatic hernia should be examined carefully for evidence of the Brachmann-de Lange syndrome because diagnosis of this condition may influence their clinical management and prognosis.

Exclusion of the branchio-oto-renal syndrome locus (EYA1) from patients with branchio-oculo-facial syndrome.

In addition to craniofacial, auricular, ophthalmologic, and oral anomalies, the distinctive phenotype of the branchio-oculo-facial (BOF) syndrome (MIM 113620) includes skin defects in the neck or infra/supra-auricular region. These unusual areas of thin, erythematous wrinkled skin differ from the discrete cervical pits, cysts, and fistulas of the branchio-oto-renal (BOR) syndrome (MIM 113650). Although the BOF and BOR syndromes are sufficiently distinctive that they should not be confused, both can be associated with nasolacrimal duct stenosis, deafness, prehelical pits, malformed pinna, and renal anomalies. Furthermore, a reported father and son [Legius et al., 1990, Clin Genet 37:347-500] had features of both conditions. It was not clear whether they had an atypical presentation of either BOR or BOF syndrome, or represented a private syndrome. In light of these issues, we selected the BOR locus (EYA1) as a possible gene mutation for the BOF syndrome. In five BOF patients, there were no mutations detected in the EYA1 gene, suggesting that it is not allelic to the BOR syndrome.

Trisomy 12 mosaicism confirmed in multiple organs from a liveborn child.

This patient, in whom trisomy 12 mosaicism was confirmed in multiple organs, is the fifth case diagnosed postnatally and the first reported for whom a meiotic origin of the trisomy, maternal meiosis I, was determined. Mosaic aneuploidy was suspected because of pigmentary dysplasia, a frequent but non-specific finding in chromosomal mosaicism. The severe phenotype of this child, who died in infancy with a complex heart malformation, was probably a result of the high percentage of trisomic cells. Cytogenetic and interphase fluorescent in situ hybridization analyses showed a highly variable distribution of aneuploid cells in the nine tissues studied, from none in blood and ovary to 100% in spleen and liver. The trisomy arose meiotically with apparent post-zygotic loss of one of the chromosomes 12; uniparental disomy for this chromosome in the diploid cell line was excluded. The phenotype of the cases reported in living or liveborn individuals has been extremely variable, ranging from the present case, in which the child died in infancy with multiple malformations and pigmentary dysplasia, to a fortuitous finding in an adult studied for infertility. The variation in severity is probably determined by the proportion and distribution of the trisomic cells, which is linked to the timing of the non-disjunctional error.

Lymphedema in Noonan syndrome: clues to pathogenesis and prenatal diagnosis and review of the literature.

The Noonan syndrome (NS) is a true multiple congenital anomalies (MCA) syndrome with numerous manifestations. An association with lymphedema has been noted, but its pathogenesis is not fully understood. Nine new cases and a review of the literature explore the role of lymphedema in NS, including its pathogenesis, presentations, and phenotypic effects. Consideration is given to developmental stage at time of onset, chronicity, resolution, and anatomic site. It appears likely that lymphedema is a much more frequent concomitant in NS than previously realized. The major source of lymphedema in NS appears to be a presently undefined dysplasia of lymphatic vessels of unknown cause. Further study of lymphedema may provide an understanding of its role in shaping the NS phenotype. Comparison with other MCA syndromes and animal models is made in this regard. Relevance to prenatal diagnosis and treatment is discussed.

Smith-Lemli-Opitz syndrome-type II: multiple congenital anomalies with male pseudohermaphroditism and frequent early lethality.

In 1964, Smith et al described a syndrome of microcephaly, growth and mental retardation, unusual facial appearance, syndactyly of toes 2 and 3, and genital abnormalities. Major structural malformations and early death have been uncommon in the many subsequent literature reports. We report on 19 infants with a phenotype we propose to call Smith-Lemli-Opitz syndrome (SLOS)-Type II, in which major structural abnormalities, male pseudohermaphroditism, and early lethality are common. Of these 19 patients, 18 had postaxial hexadactyly, 16 had congenital heart defect, 13 had cleft palate, and 10 had cataracts. Unusual findings seen in these patients at autopsy included Hirschsprung "disease" in five patients, unilobated lungs in six, large adrenals in four, and pancreatic islet cell hyperplasia in three. Comparison of our cases to 19 similar literature cases suggests the existence of a distinct phenotype that may be separate from SLOS as originally described. It is also inherited as an autosomal recessive, as documented by occurrence in one pair of sibs in this study and recurrence in three reported families.

Diagnostic criteria for Walker-Warburg syndrome.

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder manifest by characteristic brain and eye malformations. We reviewed data on 21 of our patients and an additional 42 patients from the literature. From this review, we expand the phenotype to include congenital muscular dystrophy (CMD) and cleft lip and/or palate (CLP), and revise the diagnostic criteria. Four abnormalities were present in all patients checked for these anomalies: type II lissencephaly (21/21), cerebellar malformation (20/20), retinal malformation (18/18), and CMD (14/14). We propose that these comprise necessary and sufficient diagnostic criteria for WWS. Two other frequently observed abnormalities, ventricular dilatation with or without hydrocephalus (20/21) and anterior chamber malformation (16/21), are helpful but not necessary diagnostic criteria because they were not constant. All other abnormalities occurred less frequently. Congenital macrocephaly with hydrocephalus (11/19) was more common than congenital microcephaly (3/19). Dandy-Walker malformation (10/19) was sometimes associated with posterior cephalocele (5/21). Additional abnormalities included slit-like ventricles (1/21), microphthalmia (8/21), ocular colobomas (3/15), congenital cataracts (7/20), genital anomalies in males (5/8), and CLP (4/21). Median survival in our series was 9 months. A related autosomal recessive disorder, Fukuyama congenital muscular dystrophy, consists of similar but less severe brain changes and CMD. It differs from WWS because of consistently less frequent and severe cerebellar and retinal abnormalities. We think that WWS is identical to "cerebro-oculo-muscular syndrome" and "muscle, eye, and brain disease."

Male infant with ichthyosis, Kallmann syndrome, chondrodysplasia punctata, and an Xp chromosome deletion.

We report on a male infant with X-linked ichthyosis, X-linked Kallmann syndrome, and X-linked recessive chondrodysplasia punctata (CPXR). Chromosome analysis showed a terminal deletion with a breakpoint at Xp22.31, inherited maternally. This patient confirms the localization of XLI, XLK, and CPXR to this region of the X chromosome and represents an example of a "contiguous gene syndrome." A comparison of the manifestations of patients with CPXR, warfarin embryopathy, and vitamin K epoxide reductase deficiency shows a remarkable similarity. However, vitamin K epoxide reductase deficiency does not appear to be the cause of CPXR. We propose that CPXR may be due to a defect in a vitamin K-dependent bone protein such as vitamin K-dependent bone carboxylase, osteocalcin, or matrix Gla protein.

New mesomelic dysplasia with absent fibulae and triangular tibiae.

We report on two unrelated, sporadic cases of a mesomelic dysplasia characterized by absence of fibulae and severely hypoplastic, triangular-shaped tibiae. Moderate mesomelic shortness was present in the upper limbs with proximal widening of the ulnae. There was also axial skeletal involvement in both cases, characterized radiographically by an abnormal pelvis and marked bilateral glenoid hypoplasia. These cases appear to represent a new form of mesomelic dysplasia distinct from those previously delineated.

Mild autosomal dominant hypophosphatasia: in utero presentation in two families.

We describe four pregnancies in two families in which mild hypophosphatasia, apparently transmitted as an autosomal dominant trait, manifested in utero as severe long bone bowing. Postnatally, there was spontaneous improvement of the skeletal defects. Recognition of this presentation for hypophosphatasia by family investigation and assessment of the fetal skeleton for degree of ossification and chest size using ultrasonography is important. The prognosis for this condition is considerably better than for more severe forms of hypophosphatasia and for many other disorders that cause skeletal defects with long bone bowing in utero.