SIL1 mutations and clinical spectrum in patients with Marinesco-Sjogren syndrome

Marinesco-Sjögren syndrome is a rare autosomal recessive multisystem disorder featuring cerebellar ataxia, early-onset cataracts, chronic myopathy, variable intellectual disability and delayed motor development. More recently, mutations in the SIL1 gene, which encodes an endoplasmic reticulum resident co-chaperone, were identified as the main cause of Marinesco-Sjögren syndrome. Here we describe the results of SIL1 mutation analysis in 62 patients presenting with early-onset ataxia, cataracts and myopathy or combinations of at least two of these. We obtained a mutation detection rate of 60% (15/25) among patients with the characteristic Marinesco-Sjögren syndrome triad (ataxia, cataracts, myopathy) whereas the detection rate in the group of patients with more variable phenotypic presentation was below 3% (1/37). We report 16 unrelated families with a total of 19 different SIL1 mutations. Among these mutations are 15 previously unreported changes, including single- and multi-exon deletions. Based on data from our screening cohort and data compiled from the literature we found that SIL1 mutations are invariably associated with the combination of a cerebellar syndrome and chronic myopathy. Cataracts were observed in all patients beyond the age of 7 years, but might be missing in infants. Six patients with SIL1 mutations had no intellectual disability, extending the known wide range of cognitive capabilities in Marinesco-Sjögren syndrome to include normal intelligence. Modestly constant features were somatic growth retardation, skeletal abnormalities and pyramidal tract signs. Examination of mutant SIL1 expression in cultured patient lymphoblasts suggested that SIL1 mutations result in severely reduced SIL1 protein levels irrespective of the type and position of mutations. Our data broaden the SIL1 mutation spectrum and confirm that SIL1 is the major Marinesco-Sjögren syndrome gene. SIL1 patients usually present with the characteristic triad but cataracts might be missing in young children. As cognitive impairment is not obligatory, patients without intellectual disability but a Marinesco-Sjögren syndrome-compatible phenotype should receive SIL1 mutation analysis. Despite allelic heterogeneity and many families with private mutations, the phenotype related to SIL1 mutations is relatively homogenous. Based on SIL1 expression studies we speculate that this may arise from a uniform effect of different mutations on protein expression.

Mutations in BICD2, which encodes a golgin and important motor adaptor, cause congenital autosomal-dominant spinal muscular atrophy

Spinal muscular atrophy (SMA) is a heterogeneous group of neuromuscular disorders caused by degeneration of lower motor neurons. Although functional loss of SMN1 is associated with autosomal-recessive childhood SMA, the genetic cause for most families affected by dominantly inherited SMA is unknown. Here, we identified pathogenic variants in bicaudal D homolog 2 (Drosophila) (BICD2) in three families afflicted with autosomal-dominant SMA. Affected individuals displayed congenital slowly progressive muscle weakness mainly of the lower limbs and congenital contractures. In a large Dutch family, linkage analysis identified a 9q22.3 locus in which exome sequencing uncovered c.320C>T (p.Ser107Leu) in BICD2. Sequencing of 23 additional families affected by dominant SMA led to the identification of pathogenic variants in one family from Canada (c.2108C>T [p.Thr703Met]) and one from the Netherlands (c.563A>C [p.Asn188Thr]). BICD2 is a golgin and motor-adaptor protein involved in Golgi dynamics and vesicular and mRNA transport. Transient transfection of HeLa cells with all three mutant BICD2 cDNAs caused massive Golgi fragmentation. This observation was even more prominent in primary fibroblasts from an individual harboring c.2108C>T (p.Thr703Met) (affecting the C-terminal coiled-coil domain) and slightly less evident in individuals with c.563A>C (p.Asn188Thr) (affecting the N-terminal coiled-coil domain). Furthermore, BICD2 levels were reduced in affected individuals and trapped within the fragmented Golgi. Previous studies have shown that Drosophila mutant BicD causes reduced larvae locomotion by impaired clathrin-mediated synaptic endocytosis in neuromuscular junctions. These data emphasize the relevance of BICD2 in synaptic-vesicle recycling and support the conclusion that BICD2 mutations cause congenital slowly progressive dominant SMA.

Autosomal recessive spastic ataxia of Charlevoix Saguenay (ARSACS): expanding the genetic, clinical and imaging spectrum

BACKGROUND

Mutations in SACS, leading to autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), have been identified as a frequent cause of recessive early-onset ataxia around the world. Here we aimed to enlarge the spectrum of SACS mutations outside Quebec, to establish the pathogenicity of novel variants, and to expand the clinical and imaging phenotype.

METHODS

Sequencing of SACS in 22 patients with unexplained early-onset ataxia, assessment of novel SACS variants in 3.500 European control chromosomes and extensive phenotypic investigations of all SACS carriers.

RESULTS

We identified 11 index patients harbouring 17 novel SACS variants. 9/11 patients harboured two variants of at least probable pathogenicity which were not observed in controls and, in case of missense mutations, were located in highly conserved domains. These 9 patients accounted for at least 11% (9/83) in our series of unexplained early onset ataxia subjects. While most patients (7/9) showed the classical ARSACS triad, the presenting phenotype reached from pure neuropathy (leading to the initial diagnosis of Charcot-Marie-Tooth disease) in one subject to the absence of any signs of neuropathy in another. In contrast to its name "spastic ataxia", neither spasticity (absent in 2/9=22%) nor extensor plantar response (absent in 3/9=33%) nor cerebellar ataxia (absent in 1/9=11%) were obligate features. Autonomic features included urine urge incontinence and erectile dysfunction. Apart from the well-established MRI finding of pontine hypointensities, all patients (100%) showed hyperintensities of the lateral pons merging into the (thickened) middle cerebellar peduncles. In addition, 63% exhibited bilateral parietal cerebral atrophy, and 63% a short circumscribed thinning of the posterior midbody of the corpus callosum. In 2 further patients with differences in important clinical features, VUS class 3 variants (c.1373C>T [p.Thr458Ile] and c.2983 G>T [p.Val995Phe]) were identified. These variants were, however, also observed in controls, thus questioning their pathogenic relevance.

CONCLUSIONS

We here demonstrate that each feature of the classical ARSACS triad (cerebellar ataxia, spasticity and peripheral neuropathy) might be missing in ARSACS. Nevertheless, characteristic MRI features - which also extend to supratentorial regions and involve the cerebral cortex - will help to establish the diagnosis in most cases.

Pontocerebellar hypoplasia type 1: clinical spectrum and relevance of EXOSC3 mutations

OBJECTIVES

Pontocerebellar hypoplasia with spinal muscular atrophy, also known as PCH1, is a group of autosomal recessive disorders characterized by generalized muscle weakness and global developmental delay commonly resulting in early death. Gene defects had been discovered only in single patients until the recent identification of EXOSC3 mutations in several families with relatively mild course of PCH1. We aim to genetically stratify subjects in a large and well-defined cohort to define the clinical spectrum and genotype-phenotype correlation.

METHODS

We documented clinical, neuroimaging, and morphologic data of 37 subjects from 27 families with PCH1. EXOSC3 gene sequencing was performed in 27 unrelated index patients of mixed ethnicity.

RESULTS

Biallelic mutations in EXOSC3 were detected in 10 of 27 families (37%). The most common mutation among all ethnic groups was c.395A>C, p.D132A, responsible for 11 (55%) of the 20 mutated alleles and ancestral in origin. The mutation-positive subjects typically presented with normal pregnancy, normal birth measurements, and relative preservation of brainstem and cortical structures. Psychomotor retardation was profound in all patients but lifespan was variable, with 3 subjects surviving beyond the late teens. Abnormal oculomotor function was commonly observed in patients surviving beyond the first year. Major clinical features previously reported in PCH1, including intrauterine abnormalities, postnatal hypoventilation and feeding difficulties, joint contractures, and neonatal death, were rarely observed in mutation-positive infants but were typical among the mutation-negative subjects.

CONCLUSION

EXOSC3 mutations account for 30%-40% of patients with PCH1 with variability in survival and clinical severity that is correlated with the genotype.

Genetic tests in sports medicine - many studies, little impact

Genetic research in sports has a history of more than 40 years of endeavouring to find out which genetic factors can predict the performance of an athlete. With increasing knowledge of the human genome and availability of genetic testing the market of direct-to-consumer genetic tests has exploded in recent years. There are tests for genetic variants for medical and general health issues, but there are also 'lifestyle' tests, including tests for indicators for sport performance. The human gene map for fitness and performance includes hundreds of genes that play a role in cardiorespiratory endurance, muscle strength, exercise tolerance, body composition and energy metabolism. However, there is currently no evidence that genotyping an individual is superior to traditional physiological tests in predicting athletic performance.

The impact of genetic test results is much higher in certain medical conditions which are associated with significant health risks when performing competitive sport. These are generally rare inherited disorders, mostly resulting in cardiovascular dysfunction. There are major ethical issues as to whether genetic or clinical pre-participation screenings should be applied to the population in order to prevent disease or death during sport. Some of these issues will be addressed in this article.

Stress and coping in parents of children and adolescents with spinal muscular atrophy

BACKGROUND

Chronic illness and disability is not only associated with higher rates of behavioural problems in children, but also parental stress which requires active coping. The aim of the study was to analyse stress and coping, as well as their mediating variables, in parents of children and adolescents with Spinal Muscular Atrophy (SMA).

METHOD

96 children and adolescents with SMA aged 6;0 to 18;11 years were compared to 59 age, sex and SES matched controls.

RESULTS

Parental stress was measured with the QRS, coping with the F-COPES and social support with the F-SOZU questionnaires.Parental stress was significantly higher in the SMA families for the total score and all subscales of the QRS. Stress was higher in families with severely affected SMA types I and II. The greatest percentage of variance contributing to stress could be explained by lack of social support, degree of disability and behavioural problems in the child. Although social support was reduced, the actual coping abilities of the families did not differ.

CONCLUSION

Families with children and adolescents with SMA show high degrees of stress and strain which are associated with the severity of the disease, reduced social support and child behaviour. Despite these stresses they manage and cope no differently from families with healthy children.

Life with too much polyprenol: polyprenol reductase deficiency

Congenital disorders of glycosylation (CDG) are caused by a dysfunction of glycosylation, an essential step in the manufacturing process of glycoproteins. This paper focuses on a 6-year-old patient with a new type of CDG-I caused by a defect of the steroid 5α reductase type 3 gene (SRD5A3). The clinical features were psychomotor retardation, pathological nystagmus, slight muscular hypotonia and microcephaly. SRD5A3 was recently identified encoding the polyprenol reductase, an enzyme catalyzing the final step of the biosynthesis of dolichol, which is required for the assembly of the glycans needed for N-glycosylation. Although an early homozygous stop-codon (c.57G>A [W19X]) with no functional protein was found in the patient, about 70% of transferrin (Tf) was correctly glycosylated. Quantification of dolichol and unreduced polyprenol in the patient's fibroblasts demonstrated a high polyprenol/dolichol ratio with normal amounts of dolichol, indicating that high polyprenol levels might compete with dolichol for the initiation of N-glycan assembly but without supporting normal glycosylation and that there must be an alternative pathway for dolichol biosynthesis.

Pregnancy course and outcome in women with hereditary neuromuscular disorders: comparison of obstetric risks in 178 patients

OBJECTIVE

Information about pregnancy and delivery in hereditary neuromuscular disorders (NMD) is limited and largely restricted to small case series and single case reports. Further data of obstetric histories in clinically and genetically defined subgroups are required.

STUDY DESIGN

We reviewed the obstetric histories of 178 patients with myotonic dystrophy type 1 (DM1) and 2 (DM2), Charcot-Marie-Tooth disease (CMT), spinal muscular atrophy (SMA), limb-girdle muscular dystrophy (LGMD), facioscapulohumeral muscular dystrophy (FSHD), and congenital myopathy (CM) by means of questionnaires and medical reports. Patients were recruited in the period 1992-2010 after they had at least completed one pregnancy. A total of 380 pregnancies resulting in 315 children were documented.

RESULTS

Compared to the normal German population, the number of miscarriages and hypertensive diseases in pregnancy was not increased in the cohort. Patients with NMD delivered more frequently by vaginal operations (8.9-18.2%) and by cesarean births with significantly high rates in DM1 (36.7%) and SMA (42.4%). Preterm deliveries were recorded in 30.7% of DM1, 12.6% of DM2, and 29.4% of SMA gestations. Abnormal fetal presentation occurred significantly more frequently in DM1 (34.6%) and LGMD (26.7%) deliveries and was a feature of chairbound patients. Considering a possible influence of pregnancy on the disease course, about half of LGMD, one-third of SMA, and one fifth of CMT patients reported a deterioration of symptoms in pregnancy. Neonatal outcome was favorable in all NMD but DM1, where infantile morbidity and mortality is often but not exclusively related to congenitally affected children.

CONCLUSION

Our data are important for obstetric care and genetic counseling of women with NMD who are contemplating pregnancy.

A phenotype map for 14q32.3 terminal deletions

Detailed molecular-cytogenetic studies combined with thorough clinical characterization are needed to establish genotype-phenotype correlations for specific chromosome deletion syndromes. Although many patients with subtelomeric deletions have been reported, the phenotype maps for many of the corresponding syndromes, including the terminal deletion 14q syndrome, are only slowly emerging. Here, we report on five patients with terminal partial monosomy of 14q32.3 and characteristic features of terminal deletion 14q syndrome. Four of the patients carry de novo terminal deletions of 14q, three of which have not yet been reported. One patient carries an unbalanced translocation der(14)t(9;14)(q34.3;q32.3). Minimum deletion sizes as determined by molecular karyotyping and FISH are 5.82, 5.56, 4.17, 3.54, and 3.29 Mb, respectively. Based on our findings and a comprehensive review of the literature, we refine the phenotype map for typical clinical findings of the terminal deletion 14q syndrome (i.e., intellectual disability/developmental delay, muscular hypotonia, postnatal growth retardation, microcephaly, congenital heart defects, genitourinary malformations, ocular coloboma, and several dysmorphic signs). Combining this phenotype map with benign copy-number variation data available from the Database of Genomic Variants, we propose a small region critical for certain features of the terminal deletion 14q syndrome which contains only seven RefSeq genes.

SETX gene mutation in a family diagnosed autosomal dominant proximal spinal muscular atrophy

Autosomal dominant proximal spinal muscular atrophy (ADSMA) is a rare disorder with unknown gene defects in the majority of families. Here we describe a family where the diagnosis of juvenile and adult onset ADSMA was made in three individuals. Because of retained tendon reflexes an atypical course of juvenile amyotrophic lateral sclerosis (ALS4) was considered. SETX gene sequencing revealed the previously reported heterozygous missense mutation c.1166T<C, L389S in the patients. Moreover the index patient and his sister had an earlier age at onset (10 and 15 years) and a more pronounced weakness as compared to their father with an age at onset of 35 years. Both sibs additionally carried a second SETX missense mutation of unknown function V891A in trans. Altogether these results expand the phenotype associated with SETX mutations supporting the notion that patients with ADSMA should be investigated for SETX mutations.

Recurrence risks of hypertensive diseases in pregnancy after HELLP syndrome

AIM

To determine the recurrence risk for hypertensive diseases in pregnancy after HELLP (Hemolysis Elevated Liver enzymes and Low Platelets) syndrome in a first pregnancy.

METHODS

The study was designed as a cohort study investigating 148 Caucasian primiparae with a diagnosis of HELLP syndrome in a first pregnancy and at least one subsequent pregnancy conducted beyond the 24th gestational week. Diagnoses were verified by reviewing medical records and classified according to ISSHP (International Society for the Study of Hypertension in Pregnancy) criteria. The recurrence risk of HELLP syndrome or other hypertensive disorders in the subsequent pregnancy was calculated with regard to disease severity in the index pregnancy.

RESULTS

Among 148 pregnancies subsequent to HELLP syndrome, 56.1% of the women were normotensive. The recurrence rate was 12.8% for HELLP syndrome, 16.2% for pre-eclampsia, and 14.2% for gestational hypertension only. Women with HELLP syndrome ≤32 gestational weeks tended to show a greater risk of complicated subsequent pregnancies compared to women presenting with HELLP after 32 gestational weeks.

CONCLUSIONS

Women with a diagnosis of HELLP syndrome are at a strongly increased risk of recurrent HELLP syndrome, pre-eclampsia or gestational hypertension, however, currently no clinical or laboratory parameters allow the prediction of recurrence risk in any individual case.

Primary pulmonary hypertension, congenital heart defect, central nervous system malformations, hypo- and aplastic toes: another case of Yunis-Varón syndrome or report of a new entity

Here we describe a patient with a new malformation syndrome which shows similarities with Yunis-Varon syndrome (YVS). Prenatal presentation included polyhydramnios, increased nuchal translucency, and bilateral hydrothoraces requiring pigtail insertion. Postnatal presentation revealed primary pulmonary hypertension (PPH), persistent hydrothoraces, one atrial and two ventricular septal defects, hypoplasia of the corpus callosum and cerebellar vermis, dilated interhemispheric ventricles, severe developmental delay with general muscular hypotonia, retinal anomalies, sparse scalp hair, sparse eyebrows and eyelashes, hypo- and aplastic nails, low-set dysplastic ears, loose nuchal skin, hypo- and aplastic distal phalanges of the toes as well as postnatal failure to thrive. High resolution molecular karyotyping in the patient did not reveal any causative chromosomal aberration. Since one patient with YVS and PPH has been previously reported, we assume a similar pathogenic pathway. However, molecular confirmation of the clinical diagnosis is not yet possible. It remains uncertain if the presented syndrome can be classified as YVS with PPH or if it constitutes a new YVS like entity.

Two Adult Patients with Ellis-van Creveld Syndrome Extending the Clinical Spectrum

Ellis-van Creveld (EvC) syndrome is a rare autosomal recessive malformation syndrome with the main features cardiac defects, postaxial hexadactyly, mesomelic shortening of the limbs, short ribs, dysplastic nails and teeth, oral frenula and various other abnormalities while mental function is normal. We describe 2 adult EvC patients with the cardinal skeletal features of mesomelic short stature and severe, progressive genu valgum deformity, resulting from loss of function mutations in the EVC genes. While the genu valgum was the predominating and disabling feature in patient 1, patient 2 showed acroosteolyses in the distal phalanges and a symmetrical synostosis of metacarpals in his hands. Moreover, patient 2 developed synostoses in the additional fingers in adolescence which had not been present at the age of 12 years, suggesting a further progression of skeletal disease. Joint fusion of phalanges so far has not been reported in EvC syndrome. Our data further expand the phenotypic spectrum of EvC related skeletal malformations and contribute important new information on the clinical course of EvC syndrome with increasing age.

Digital necroses and vascular thrombosis in severe spinal muscular atrophy

Infantile spinal muscular atrophy (SMA) caused by homozygous SMN1 gene deletions/mutations is characterized by neuronal loss and axonopathy of motor neurons. We report two unrelated patients with severe SMA type I who had only one SMN2 copy and developed ulcerations and necroses of the fingers and toes. Sural nerve biopsy was normal in patient 1, whose affected skin displayed necroses and thrombotic occlusions of small vessels. Corresponding to a mouse model and other patients with similar findings, we believe that severe survival motor neuron (SMN) deficiency may present as vasculopathy.

Andermann syndrome can be a phenocopy of hereditary motor and sensory neuropathy--report of a discordant sibship with a compound heterozygous mutation of the KCC3 gene

Andermann syndrome is a rare autosomal recessive disorder characterized by agenesis of the corpus callosum (ACC), progressive motor-sensory neuropathy, mental retardation and facial features. We report on two siblings with the clinical picture of a demyelinating hereditary motor and sensory neuropathy (HMSN), where only the presence of ACC in the younger brother pointed to the diagnosis of Andermann syndrome. Mutation analysis of the KCC3 (SLC12A6) gene showed a compound heterozygous mutation; a maternal missense mutation c.1616G>A (p.G539D) and a paternal splice mutation c.1118+1G>A in both siblings. We hypothesize that mutations of the KCC3 gene may result in non-syndromic childhood onset HMSN.