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MYH9-related disorders: a rare cause of neonatal thrombocytopaenia.

ABSTRACT: Myosin heavy chain 9-related disorders (MYH9RD) are a genetic condition characterised by large platelets and thrombocytopaenia. The May-Hegglin anomaly (MHA), an uncommon condition with a potential risk of bleeding complications once thought to be separate, is now known to be part of MYH9RD.There are very limited data on the clinical course and neonatal/paediatric?outcome in children with MHA. We present the case of a newborn with a normal physical examination whose mother had MHA. Peripheral blood examination revealed a platelet count of 16×109/L with giant platelets and neutrophils containing Döhle bodies. Neonatal brain ultrasound examination showed no haemorrhage. The infant received three platelet transfusions during the first 29 days of life, remaining asymptomatic. The genetic molecular test was positive for MYH9RD. It is important to identify at-risk infants with this condition and to initiate therapy to prevent related complications, if needed, in a multidisciplinary team approach.

SUBMITTER: Marques MI

PROVIDER: S-EPMC6067146 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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MYH9-related disorders: a rare cause of neonatal thrombocytopaenia.

Marques Maria Inês MI Carrington Queiró Luísa L Prior Ana Rita AR Lopo Tuna Madalena M

BMJ case reports 20180730

Myosin heavy chain 9-related disorders (MYH9RD) are a genetic condition characterised by large platelets and thrombocytopaenia. The May-Hegglin anomaly (MHA), an uncommon condition with a potential risk of bleeding complications once thought to be separate, is now known to be part of MYH9RD.There are very limited data on the clinical course and neonatal/paediatric outcome in children with MHA. We present the case of a newborn with a normal physical examination whose mother had MHA. Peripheral bl ...[more]

PMID: 30061125

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Project description:Estimates of the frequencies of rare disorders vary from country to country; the global average defined prevalence is 40 per 100?000 (0.04%). Some occur in only one or a few patients. However, collectively rare disorders are fairly common, affecting 6-8% of the US population, or about 30 million people, and a similar number in the European Union. Most of them affect children and most are genetically determined. Diagnosis can be difficult, partly because of variable presentations and partly because few clinicians have experience of individual rare disorders, although they may be assisted by searching databases. Relatively few rare disorders have specific pharmacological treatments (so-called orphan drugs), partly because of difficulties in designing trials large enough to determine benefits and harms alike. Incentives have been introduced to encourage the development of orphan drugs, including tax credits and research aids, simplification of marketing authorization procedures and exemption from fees, and extended market exclusivity. Consequently, the number of applications for orphan drugs has grown, as have the costs of using them, so much so that treatments may not be cost-effective. It has therefore been suggested that not-for-profit organizations that are socially motivated to reduce those costs should be tasked with producing them. A growing role for patient organizations, improved clinical and translational infrastructures, and developments in genetics have also contributed to successful drug development. The translational discipline of clinical pharmacology is an essential component in drug development, including orphan drugs. Clinical pharmacologists, skilled in basic pharmacology and its links to clinical medicine, can be involved at all stages. They can contribute to the delineation of genetic factors that determine clinical outcomes of pharmacological interventions, develop biomarkers, design and perform clinical trials, assist regulatory decision making, and conduct postmarketing surveillance and pharmacoepidemiological and pharmacoeconomic assessments.

Project description:The application of genome sequencing in patients with intellectual disability and congenital anomalies (ID/CA) typically identifies causative mutations only in a minority of cases. We hypothesized that some cases of ID/CA are caused by epigenetic aberrations that dysregulate normal genome function, and that these would be missed by conventional sequencing approaches. We performed Illumina 450k DNA methylation profiling in ~500 individuals with ID/CA, who were negative for causative mutations by microarray, exome- and/or whole genome sequencing. We screened patient methylation profiles for epimutations absent in ~1,500 controls, and validated these by bisulfite sequencing, revealing that epimutations represent large methylation changes specifically on one allele. Parental studies show that approximately half represent de novo events, a rate significantly higher than that seen in controls. We identified seven recurrent events, two of which (FMR1, MEG3) have known disease associations, validating our method for detecting pathogenic epimutations. From large-scale sequencing, population and expression studies we conclude that epimutations are: (i) Frequently associated with extreme outlier and mono-allelic gene expression, with an impact comparable to loss-of-function mutations; (ii) Generally conserved across multiple tissues within an individual, validating the use of blood DNA to study ID/CA; (iii) Can occur secondary to cis-linked regulatory mutations, providing a rationale for interpreting non-coding genetic variants; (iv) Occur sporadically with a remarkably high de novo rate, and (v) Exhibit non-Mendelian inheritance, likely being reset between generations by epigenetic reprogramming during embryogenesis. We conclude that epimutations underlie 5-10% of patients with ID/CA who are refractory to conventional mutation screening, and propose that epigenome profiling represents a promising method for the study of human disease that complements sequence-based approaches.

Dataset Information

MYH9-related disorders: a rare cause of neonatal thrombocytopaenia.

Publications

MYH9-related disorders: a rare cause of neonatal thrombocytopaenia.

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