RESUMO
IRF2BPL gene variants have recently been associated to developmental disability and epilepsy in children and movement disorders in adults. So far, only few cases have been reported; here we present four novel cases identified by exome sequencing, while investigating developmental delay, adult-onset cerebellar ataxia or regression.
RESUMO
Spinocerebellar ataxias and Huntington disease are heritable, adult onset, neurodegenerative disorders of movement. Both are autosomal dominant and caused by expansions in trinucleotide sequences in several genes. Because these expansions are associated with an almost complete penetrance, genetic tests are available at the diagnostic and predictive level. In this study, we describe the expectations and issues raised during pre-test interviews for genetic counselling for these diseases. Data from pre-test interviews with 97 patients and at-risk relatives for spinocerebellar ataxia (SCA) or Huntington disease was comprised of close-ended questions (demographics, personal and current disease history) and open-ended questions, where individuals were asked to describe their hopes and expectations on the genetic counselling evaluation and also their degree of knowledge about genetics and medical genetics. Amongst the main expectations identified in patients and at-risk relatives, issues related to the aetiological diagnosis and/or disclosure of the at-risk status were those most frequently mentioned (57 %). Improvement in quality of life was another identified issue (17 %). Interestingly, the issue of inheritance/transmission was identified as the main expectation by a minority of individuals (3 %). Pre-test interviews are valuable tools to identify issues raised by consultands and promote a better communication between the patient, family and the genetic counselling team.
RESUMO
Segmental uniparental isodisomy (iUPD) is a rare genetic event that may cause aberrant expression of imprinted genes, and reduction to homozygosity of a recessive mutation. Transient neonatal diabetes mellitus (TNDM) is typically caused by imprinting aberrations in chromosome 6q24 TNDM differentially-methylated region (DMR). Approximately, 15.12 Mb upstream in 6q22-q23 is located LAMA2, the gene responsible of merosin-deficient congenital muscular dystrophy type 1A (MDC1A). We investigated a patient diagnosed both with TNDM and MDC1A, born from a twin dichorionic discordant pregnancy. Parents are first-degree cousins. Methylation sensitive-PCR of the imprinted 6q24 TNDM CpG island showed only the non-methylated (paternal) allele. Microsatellite markers and SNP array profiling disclosed normal biparental inheritance at 6p and a segmental paternal iUPD, between 6q22.33 and 6q27. Sequencing of LAMA2 exons showed a homozygous frameshift mutation, c.7490_7493dupAAGA, which predicts p.Asp2498GlufsX4, in exon 54. Her father, but not her mother, was a carrier of the mutation. While segmental paternal iUPD6 causing TNDM was reported twice, there are no previous reports of MDC1A caused by this event. This is a child with two genetic disorders, yet neither is caused by the parental consanguinity, which reinforces the importance of considering different etiological mechanisms in the genetic clinic.
