Clinical utility gene card for: Proximal spinal muscular atrophy (SMA) - update 2015

New Feeding Assessment Scale for individuals with genetic syndromes: Validity and reliability in the CHARGE syndrome population

AIM

To develop a feeding scale for parents/care givers of individuals of all ages with genetic syndromes experiencing extensive feeding and swallowing problems. Second, to assess its validity and reliability in CHARGE syndrome.

METHODS

The new Feeding Assessment Scale (FAS) was adapted from a scale for children who need prolonged tube feeding (Paediatric Assessment Scale for Severe Feeding Problems, PASSFP). Ten parents piloted the new scale before it was sent out with the PASSFP and feeding history questions. A subset completed the new scale again 4-8 weeks later.

RESULTS

One hundred parents of individuals with CHARGE syndrome participated from around the world. The new scale had good construct validity, with a significant effect for an increased number of feeding risk factors having higher scale scores (P < 0.001). Face validity was high, as scores significantly differed between individuals whose parents identified their feeding difficulties as very mild, mild, moderate, severe and very severe (P < 0.001). Test-retest reliability (r = 0.94, P < 0.001) and internal consistency (Cronbach's alpha 0.91) were both high. There was significant convergent validity between the new scale and the PASSFP (r = -0.79, P < 0.001).

CONCLUSIONS

This new tool is reliable and valid for parents/care givers of individuals with CHARGE syndrome. It can be used to assess the current severity of feeding difficulties and to track progress before and after treatment. It expands upon previous existing tools in that it can be used in both individuals who are not tube fed, as well as in those who are, as well as across the life-span.

A Novel Homozygous Variant of SETX Causes Ataxia with Oculomotor Apraxia Type 2

Background and Purpose

Autosomal recessive cerebellar ataxias constitute a highly heterogeneous group of neurodegenerative disorders. This study was carried out to determine the clinical and genetic causes of ataxia in two families from Pakistan.

Methods

Detailed clinical investigations were carried out on probands in two consanguineous families. Magnetic resonance imaging was performed. Exome sequencing data were examined for likely pathogenic variants. Candidate variants were checked for cosegregation with the phenotype using Sanger sequencing. Public databases including ExAC, GnomAD, dbSNP, and the 1,000 Genome Project as well as ethnically matched controls were checked to determine the frequencies of the alleles. Conservation of missense variants was ensured by aligning orthologous protein sequences from diverse vertebrate species.

Results

Reverse phenotyping identified spinocerebellar ataxia, autosomal recessive 1 [OMIM 606002, also referred to as ataxia oculomotor apraxia type 2 (AOA2)] and ataxia telangiectasia (OMIM 208900) in the two families. A novel homozygous missense mutation c.202 C>T (p.Arg68Cys) was identified within senataxin, SETX in the DNA of both patients in one of the families with AOA2. The patients in the second family were homozygous for a known variant in ataxia-telangiectasia mutated (ATM) gene: c.7327 C>T (p.Arg2443Ter). Both variants were absent from 100 ethnically matched control chromosomes and were either absent or present at very low frequencies in the public databases.

Conclusions

This report extends the allelic heterogeneity of SETX mutations causing AOA2 and also presents an asymptomatic patient with a pathogenic ATM variant.

DNA methylation in PRDM8 is indicative for dyskeratosis congenita

Dyskeratosis congenita (DKC) is associated with impaired telomere maintenance and with clinical features of premature aging. In this study, we analysed global DNA methylation (DNAm) profiles of DKC patients. Age-associated DNAm changes were not generally accelerated in DKC, but there were significant differences to DNAm patterns of healthy controls, particularly in CpG sites related to an internal promoter region of PR domain containing 8 (PRDM8). Notably, the same genomic region was also hypermethylated in aplastic anemia (AA) – another bone marrow failure syndrome. Site-specific analysis of DNAm level in PRDM8 with pyrosequencing and MassARRAY validated aberrant hypermethylation in 11 DKC patients and 27 AA patients. Telomere length, measured by flow-FISH, did not directly correlate with DNAm in PRDM8. Therefore the two methods may be complementary to also identify patients with still normal telomere length. In conclusion, blood of DKC patients reveals aberrant DNAm patterns, albeit age-associated DNAm patterns are not generally accelerated. Aberrant hypermethylation is particularly observed in PRDM8 and this may support identification and classification of bone marrow failure syndromes.