The different clinical facets of SYN1-related neurodevelopmental disorders

Synapsin-I (SYN1) is a presynaptic phosphoprotein crucial for synaptogenesis and synaptic plasticity. Pathogenic SYN1 variants are associated with variable X-linked neurodevelopmental disorders mainly affecting males. In this study, we expand on the clinical and molecular spectrum of the SYN1-related neurodevelopmental disorders by describing 31 novel individuals harboring 22 different SYN1 variants. We analyzed newly identified as well as previously reported individuals in order to define the frequency of key features associated with these disorders. Specifically, behavioral disturbances such as autism spectrum disorder or attention deficit hyperactivity disorder are observed in 91% of the individuals, epilepsy in 82%, intellectual disability in 77%, and developmental delay in 70%. Seizure types mainly include tonic-clonic or focal seizures with impaired awareness. The presence of reflex seizures is one of the most representative clinical manifestations related to SYN1. In more than half of the cases, seizures are triggered by contact with water, but other triggers are also frequently reported, including rubbing with a towel, fever, toothbrushing, fingernail clipping, falling asleep, and watching others showering or bathing. We additionally describe hyperpnea, emotion, lighting, using a stroboscope, digestive troubles, and defecation as possible triggers in individuals with SYN1 variants. The molecular spectrum of SYN1 variants is broad and encompasses truncating variants (frameshift, nonsense, splicing and start-loss variants) as well as non-truncating variants (missense substitutions and in-frame duplications). Genotype-phenotype correlation revealed that epileptic phenotypes are enriched in individuals with truncating variants. Furthermore, we could show for the first time that individuals with early seizures onset tend to present with severe-to-profound intellectual disability, hence highlighting the existence of an association between early seizure onset and more severe impairment of cognitive functions. Altogether, we present a detailed clinical description of the largest series of individuals with SYN1 variants reported so far and provide the first genotype-phenotype correlations for this gene. A timely molecular diagnosis and genetic counseling are cardinal for appropriate patient management and treatment.

POLD1 Germline Mutations in Patients Initially Diagnosed with Werner Syndrome

Segmental progeroid syndromes are rare, heterogeneous disorders characterized by signs of premature aging affecting more than one tissue or organ. A prototypic example is the Werner syndrome (WS), caused by biallelic germline mutations in the Werner helicase gene (WRN). While heterozygous lamin A/C (LMNA) mutations are found in a few nonclassical cases of WS, another 10%-15% of patients initially diagnosed with WS do not have mutations in WRN or LMNA. Germline POLD1 mutations were recently reported in five patients with another segmental progeroid disorder: mandibular hypoplasia, deafness, progeroid features syndrome. Here, we describe eight additional patients with heterozygous POLD1 mutations, thereby substantially expanding the characterization of this new example of segmental progeroid disorders. First, we identified POLD1 mutations in patients initially diagnosed with WS. Second, we describe POLD1 mutation carriers without clinically relevant hearing impairment or mandibular underdevelopment, both previously thought to represent obligate diagnostic features. These patients also exhibit a lower incidence of metabolic abnormalities and joint contractures. Third, we document postnatal short stature and premature greying/loss of hair in POLD1 mutation carriers. We conclude that POLD1 germline mutations can result in a variably expressed and probably underdiagnosed segmental progeroid syndrome.

Outcomes in children with Noonan syndrome and hypertrophic cardiomyopathy: a study from the Pediatric Cardiomyopathy Registry

BACKGROUND

Studies of cardiomyopathy in children with Noonan syndrome (NS) have been primarily small case series or cross-sectional studies with small or no comparison groups.

METHODS

We used the Pediatric Cardiomyopathy Registry database to compare the survival experience of children with NS and hypertrophic cardiomyopathy (HCM) with children with idiopathic or familial HCM and to identify clinical and echocardiographic predictors of clinical outcomes.

RESULTS

Longitudinal data in 74 children with NS and HCM and 792 children with idiopathic or familial isolated HCM were compared. Children with NS were diagnosed with HCM before 6 months old more often (51%) than children with HCM (28%) and were more likely to present with congestive heart failure (CHF) (24% vs 9%). The NS cohort had lower crude survival than the group with other HCM (P = .03), but survival did not differ after adjustment for CHF and age at diagnosis. Within the NS cohort (1-year survival 78%), a diagnosis of HCM before age 6 months with CHF resulted in 31% 1-year survival. Lower height-for-age z score (hazard ratio 0.26, P = .005) in place of CHF and lower left ventricular fractional shortening z score (hazard ratio 0.79, P = .04) also independently predicted mortality.

CONCLUSIONS

Patients with NS with HCM have a worse risk profile at presentation compared with other children with HCM, resulting in significant early mortality (22% at 1 year). Decreased height-for-age and lower, although still supranormal, left ventricular fractional shortening z score are independent predictors of mortality in patients with NS with HCM. Such patients should have an aggressive therapeutic approach including potential listing for cardiac transplantation.

Characteristics and outcomes of cardiomyopathy in children with Duchenne or Becker muscular dystrophy: a comparative study from the Pediatric Cardiomyopathy Registry

OBJECTIVE

The aim of this study was to determine in pediatric Duchenne (DMD) and Becker muscular dystrophy (BMD) or other dilated cardiomyopathies (ODCM) whether outcomes differ by diagnosis.

BACKGROUND

Children with dilated cardiomyopathy are treated as a single undifferentiated group.

METHODS

This cohort study of 128 children with DMD, 15 with BMD, and 312 with ODCM uses outcome measures of left ventricular (LV) size and function, death, heart transplant, and death or transplant.

RESULTS

At cardiomyopathy diagnosis, the DMD and BMD groups had similar mean ages (14.4 and 14.6 years), prevalence of congestive heart failure (CHF) (30% and 33%), and LV fractional shortening (FS) Z-scores (median, -5.2 for DMD and -6.7 for BMD). The BMD group had more severe mitral regurgitation (P = .05) and a higher mean LV end-diastolic dimension Z-score than the DMD group (2.9 +/- 1.5 vs 1.2 +/- 1.9, P = .002). Duchenne muscular dystrophy group survival was lower than in BMD or ODCM groups (P = .06) at 5 years (57%, 100%, and 71%, respectively). In BMD, 25% received cardiac transplants within 0.4 years of cardiomyopathy diagnosis. The combined DMD and BMD group had less LV dilation and a closer-to-normal LV FS at cardiomyopathy diagnosis than the ODCM group. After 2 years, LV dilation increased, and LV FS did not change in the combined DMD and BMD group; for ODCM patients, LV dilation did not progress, and LV FS improved.

CONCLUSIONS

Children with DMD and cardiomyopathy have a higher mortality. Becker muscular dystrophy has a high heart transplantation rate in the 5 years after diagnosis of cardiomyopathy. Serial echocardiography demonstrates a different disease course for DMD and BMD patients compared with ODCM patients.

Packed red cell transfusion does not compromise chromosome analysis in newborns

PURPOSE

Critically ill neonates are frequently transfused with packed red cells. Some of these transfused neonates also need chromosome analysis. There is a long-standing tradition in pediatrics of not performing chromosome analysis after transfusion. We wished to determine whether transfusion with packed red cells affect the cytogenetic results in neonates.

METHOD

The medical records of all neonates at the Medical College of Georgia who had had chromosome analysis between June 1995 and June 1998 were reviewed. Ten neonates had received transfusion prior to cytogenetic testing. Of these 10 infants, two had been transfused two or more times. Routine cytogenetic analysis of 20 metaphases at 550-band level had been performed on all 10 patients. Heteromorphic markers were compared in 10 randomly selected metaphases for any discrepancy. To determine whether there were theoretical reasons to delay chromosome analysis in transfused neonates, samples of irradiated, and/or filtered, and nonfiltered blood were obtained from the blood bank and analyzed for the presence of lymphocytes.

RESULTS

Prior transfusion did not affect karyotype results. A nonmosaic abnormal karyotype was found in 3 of the 10 patients. A fourth patient's karyotype was 45,X/47,XXX. This mosaicism was constitutive and consistent as demonstrated by a follow-up chromosome analysis. All other abnormal karyotypes were consistent with the dysmorphic phenotype. Randomly selected metaphases did not show any differences in the identifiable heteromorphic markers in all 10 patients. Although there was a 50% chance of patients receiving blood from a donor of opposite sex, there were no instances in which cells with a karyotype of the opposite sex were found in the patients' blood. The irradiated and filtered cultured donor blood samples did not show any metaphases. However, metaphases were seen in the cultures from nonfiltered and nonirradiated donor blood.

CONCLUSIONS

Based on these results one does not need to delay karyotyping babies who have had blood transfusions. Packed red cell transfusion in newborns does not compromise the accuracy of chromosome analysis in our study even with multiple transfusions.

Analysis of locus heterogeneity in Waardenburg syndrome types 1 and 2 using highly informative microsatellite markers

We performed linkage and locus heterogeneity analyses of Waardenburg syndrome (WS) types 1 and 2 using 9 DNA markers from 2q35-q37, including two highly polymorphic microsatellites very closely linked to the PAX3 candidate gene. None of 5 WS type 2 (WS2) families showed linkage to the PAX3 candidate region. We localized the marker D2S102 to less than 1 cM from PAX3 (lod = 33.7, theta = 0), but a complete absence of crossovers prevented determining whether it maps distal or proximal to PAX3. Study of 14 WS type 1 (WS1) families yielded a maximum lod score of 27.81 at PAX3, theta f = 0.010, theta = 0.007 assuming homogeneity. However, we found significant evidence of locus heterogeneity, with one family initially classified as WS1 unlinked to the PAX3 region. Reevaluation of the clinical features of this family revealed atypical morphology of inner canthi. This produced the appearance of dystopia canthorum and high W-index scores. While our one unlinked WS1 family exhibits atypical canthal morphology, our type 1 families with classic dystopia appear to be homogeneously linked to PAX3. These and other findings identify precautions that need to be addressed before using PAX3-linked markers for diagnostic purposes.

Mental retardation and Ullrich-Turner syndrome in cases with 45,X/46X,+mar: additional support for the loss of the X-inactivation center hypothesis

Four cases having mosaicism for a small marker or ring [45,X/46,X,+mar or 45,X/46,X,+r] chromosome were ascertained following cytogenetic studies requested because of minor anomalies (cases 1, 3, and 4) and/or short stature (cases 2 and 4). While all 4 cases had traits typical of Ullrich-Turner syndrome (UTS), cases 1, 3, and 4 had manifestations not usually present in UTS, including unusual facial appearance, mental retardation/developmental delay (MR/DD) (cases 3 and 4), and syndactylies (case 1). The facial appearances of cases 1 and 3 were similar yet distinct from that of case 4. Using fluorescence in situ hybridization (FISH), each of the markers in these 4 cases was identified as having been derived from an X chromosome. The level of mosaicism for the mar/r(X) cell line in these cases varied from 70% (case 1) to 16% (case 4) but was not apparently correlated with the presence of MR/DD. Replication studies demonstrated a probable early replication pattern for the mar/r(X) in cases 1, 3, and 4, while the marker in case 2 was apparently late replicating. To date, 41 individuals having mosaicism for a small mar/r(X) chromosome have been described. Interestingly, most of the 14 individuals having a presumedly active mar/r(X) demonstrated clinical findings atypical of UTS, including abnormal facial changes (11) and MR/DD (13). MR was noted most frequently in those cases having at least 50% mosaicism for the marker or ring. In contrast, atypical UTS facial appearance or MR/DD was not noted in 14 of the 16 cases with UTS who carried a probable late replicating marker or ring. In conclusion, although the phenotype of 45,X/46,X,mar/r(X) individuals appears to be influenced by the genetic content and degree of mosaicism for the mar/r(X), the most significant factor associated with MR/DD appears to be the activity status of the mar/r(X) chromosome. Thus, our 4 cases provide further support for the hypothesis that a lack of inactivation of a small mar/r(X) chromosome may be a factor leading to the MR and other phenotypic abnormalities seen in this subset of individuals having atypical UTS.

Characterization of seizures associated with biotinidase deficiency

Biotinidase deficiency is an autosomal recessively inherited disorder that is often characterized by neurologic abnormalities. We reviewed the clinical features of 78 symptomatic children, 11 new patients and 67 previously reported cases, to determine the frequency, type, age at onset, and the responsiveness of seizures to antiepileptic drugs and biotin therapy. Forty-three of the 78 (55%) symptomatic children had seizures, and seizures were the presenting symptom in 38% of the enzyme-deficient patients and 70% of those who had had seizures at some time. EEGs were available for 21 of these children. Sixteen were abnormal. The initially abnormal EEGs in eight of 12 infants became normal or improved with biotin therapy, whereas four continued to be abnormal. In 21 (49%) patients, the seizures were not well controlled with antiepileptic drugs. Biotin therapy stopped the seizures within 24 hours in 12 of 16 (75%) of those whose seizures were uncontrolled by anticonvulsants (five children died prior to diagnosis). Although the metabolic and cutaneous abnormalities were corrected in the remaining four children, they continued to have neurologic abnormalities. Biotinidase deficiency and a trial of biotin (5 to 10 mg) should be considered in infants less than 1 year of age with poorly controlled seizures, and biotinidase deficiency should be included in the differential diagnosis of an infant or child with unexplained seizures.

Ophthalmologic findings in biotinidase deficiency

Biotinidase deficiency is an autosomal recessively inherited metabolic disorder characterized by neurological and cutaneous manifestations and metabolic abnormalities. We studied 78 symptomatic children and found that 51% had ophthalmologic abnormalities. These include infections (30%), optic neuropathies and visual disturbances (13%), motility disturbances (13%), retinal pigment changes (4%) and pupillary findings (1%). The most commonly reported findings are optic atrophy and keratoconjunctivities. Although the disorder can be effectively treated with biotin therapy, untreated children are at risk of developing permanent neuro-ophthalmic damage.

Partial trisomy 19p: case report and natural history

Partial trisomy 19p was noted in an infant delivered at 39 weeks gestation with intrauterine growth retardation (IUGR), bilateral club feet, renal abnormalities, hearing deficit, and multiple dysmorphic features. Chromosomes obtained following amniocentesis at 32 weeks gestation revealed that the fetus was partially trisomic for 19p and partially monosomic for a portion of the terminal band of 3q, having inherited a derivative chromosome 3 from her father [46,XX,-3,+der(3)t(3;19)(q29;p13.2)pat]. The father was found to be the carrier of a balanced translocation between chromosomes 3 and 19 [46,XY,t(3;19)(q29;p13.2)]. The only other case of partial trisomy 19p previously reported was an infant with partial trisomy 19p and partial monosomy 13q who died at 59 days of age. This report by Byrne et al. [(Am J Hum Genet 1980: 32:64A] is similar to our case with respect to IUGR, small palpebral fissures, and ear anomalies.

Progressive bilateral nasal alar collapse: a dominantly inherited trait

We describe a 47-year-old woman with progressive bilateral collapse of the alae nasi first noted at age 16 years. Her dizygotic twin daughters have similar nasal collapse beginning at age 20 years. This condition appears to be inherited as a dominant trait. Although plastic surgical correction has been successful for a phenotypically similar condition due to trauma, surgical correction must be considered cautiously in individuals with an atraumative, possibly inherited, progressive form of the disorder.

Tracheomalacia in Hallermann-Streiff syndrome

We report on a white boy with Hallermann-Streiff syndrome (HSS) who also had tracheomalacia. Chronic respiratory insufficiency led to biventricular failure and death at age 6 months. There have been no previously reported cases of Hallermann-Streiff syndrome with documented tracheomalacia. However, there may be cases in which tracheomalacia may have been present, but not diagnosed. The literature contains 6 HSS cases with severe respiratory symptoms. Tracheomalacia should be considered in a patient with HSS who presents with an unusual cry, stridor, choking, or apnea. With the availability of surgery and supportive treatment, early diagnosis of tracheomalacia in these patients may prevent death and secondary neurologic insult from acute hypoxia.