Elizabeth Hopkins

Megalencephaly‐capillary malformation (MCAP) and megalencephaly‐polydactyly‐polymicrogyria‐hydrocephalus (MPPH) syndromes: Two closely related disorders of brain overgrowth and abnormal brain and body morphogenesis

The macrocephaly‐capillary malformation syndrome (M‐CM), which we here propose to rename the megalencephaly‐capillary malformation syndrome (MCAP; alternatively the megalencephaly‐capillary malformation‐polymicrogyria syndrome), and the more recently described megalencephaly‐polymicrogyria‐polydactyly‐hydrocephalus syndrome (MPPH) are two megalencephaly (MEG) disorders that involve a unique constellation of physical and neuroimaging anomalies. We compare the features in 42 patients evaluated for physical and neuroimaging characteristics of MCAP and MPPH and propose a more global view of these syndromes based on classes of developmental abnormalities that include primary MEG and growth dysregulation, developmental vascular anomalies (primarily capillary malformations), distal limb anomalies (such as syndactyly and polydactyly), cortical brain malformations (most distinctively polymicrogyria, PMG), and variable connective tissue dysplasia. Based on these classes of developmental abnormalities, we propose that MCAP diagnostic criteria include progressive MEG with either vascular anomalies or syndactyly. In parallel, we propose that MPPH diagnostic criteria include progressive MEG and PMG, absence of the vascular anomalies and syndactyly characteristic of MCAP, and absence of brain heterotopia.

High incidence of progressive postnatal cerebellar enlargement in Costello syndrome: Brain overgrowth associated with HRAS mutations as the likely cause of structural brain and spinal cord abnormalities†

Costello syndrome is a rasopathy caused by germline mutations in the proto‐oncogene HRAS. Its presentation includes failure‐to‐thrive with macrocephaly, characteristic facial features, hypertrophic cardiomyopathy, papillomata, malignant tumors, and cognitive impairment. In a systematic review we found absolute or relative macrocephaly (100%), ventriculomegaly (50%), and other abnormalities on brain and spinal cord imaging studies in 27/28 individuals. Posterior fossa crowding with cerebellar tonsillar herniation (CBTH) was noted in 27/28 (96%), and in 10/17 (59%) with serial studies posterior fossa crowding progressed. Sequelae of posterior fossa crowding and CBTH included hydrocephalus requiring shunt or ventriculostomy (25%), Chiari 1 malformation (32%), and syrinx formation (25%). Our data reveal macrocephaly with progressive frontal bossing and CBTH, documenting an ongoing process rather than a static congenital anomaly. Comparison of images obtained in young infants to subsequent studies demonstrated postnatal development of posterior fossa crowding. This process of evolving megalencephaly and cerebellar enlargement is in keeping with mouse model data, delineating abnormal genesis of neurons and glia, resulting in an increased number of astrocytes and enlarged brain volume. In Costello syndrome and macrocephaly‐capillary malformation syndrome disproportionate brain growth is the main factor resulting in postnatal CBTH and Chiari 1 malformation.

Clinical, pathological, and molecular analyses of cardiovascular abnormalities in Costello syndrome: A Ras/MAPK pathway syndrome

Cardiovascular abnormalities are important features of Costello syndrome and other Ras/MAPK pathway syndromes (“RASopathies”). We conducted clinical, pathological and molecular analyses of 146 patients with an HRAS mutation including 61 enrolled in an ongoing longitudinal study and 85 from the literature. In our study, the most common (84%) HRAS mutation was p.G12S. A congenital heart defect (CHD) was present in 27 of 61 patients (44%), usually non‐progressive valvar pulmonary stenosis. Hypertrophic cardiomyopathy (HCM), typically subaortic septal hypertrophy, was noted in 37 (61%), and 5 also had a CHD (14% of those with HCM). HCM was chronic or progressive in 14 (37%), stabilized in 10 (27%), and resolved in 5 (15%) patients with HCM; follow‐up data was not available in 8 (22%). Atrial tachycardia occurred in 29 (48%). Valvar pulmonary stenosis rarely progressed and atrial septal defect was uncommon. Among those with HCM, the likelihood of progressing or remaining stable was similar (37%, 41% respectively). The observation of myocardial fiber disarray in 7 of 10 (70%) genotyped specimens with Costello syndrome is consistent with sarcomeric dysfunction. Multifocal atrial tachycardia may be distinctive for Costello syndrome. Potentially serious atrial tachycardia may present in the fetus, and may continue or worsen in about one‐fourth of those with arrhythmia, but is generally self‐limited in the remaining three‐fourths of patients. Physicians should be aware of the potential for rapid development of severe HCM in infants with Costello syndrome, and the need for cardiovascular surveillance into adulthood as the natural history continues to be delineated.

Phenotypic analysis of individuals with Costello syndrome due to HRAS p.G13C

Costello syndrome is characterized by severe failure‐to‐thrive, short stature, cardiac abnormalities (heart defects, tachyarrhythmia, and hypertrophic cardiomyopathy (HCM)), distinctive facial features, a predisposition to papillomata and malignant tumors, postnatal cerebellar overgrowth resulting in Chiari 1 malformation, and cognitive disabilities. De novo germline mutations in the proto‐oncogene HRAS cause Costello syndrome. Most mutations affect the glycine residues in position 12 or 13, and more than 80% of patients share p.G12S. To test the hypothesis that subtle genotype–phenotype differences exist, we report the first cohort comparison between 12 Costello syndrome individuals with p.G13C and individuals with p.G12S. The individuals with p.G13C had many typical findings including polyhydramnios, failure‐to‐thrive, HCM, macrocephaly with posterior fossa crowding, and developmental delay. Subjectively, their facial features were less coarse. Statistically significant differences included the absence of multifocal atrial tachycardia (P‐value = 0.033), ulnar deviation of the wrist (P < 0.001) and papillomata (P = 0.003), and fewer neurosurgical procedures (P = 0.024). Fewer individuals with p.G13C had short stature (height below −2 SD) without use of growth hormone (P < 0.001). The noteworthy absence of malignant tumors did not reach statistical significance. Novel ectodermal findings were noted in individuals with p.G13C, including loose anagen hair resulting in easily pluckable hair with a matted appearance, different from the tight curls typical for most Costello syndrome individuals. Unusually long eye lashes requiring trimming are a novel finding we termed dolichocilia. These distinctive ectodermal findings suggest a cell type specific effect of this particular mutation. Additional patients are needed to validate these findings.

Long-term survival in TARP syndrome and confirmation of RBM10 as the disease-causing gene.

TARP syndrome, comprising Talipes equinovarus, atrial septal defect (ASD), Robin sequence (micrognathia, glossoptosis, and cleft palate), and persistence of the left superior vena cava, is an X‐linked condition with pre‐ or postnatal lethality in affected males. Based on linkage studies and massively parallel sequencing of X‐chromosome exons in two families, the disease‐causing gene was identified as RBM10. We identified a maternally inherited frameshift mutation in an unrelated patient, confirming RBM10 as the disease gene. This is the first reported individual with TARP syndrome who survived past early infancy, thus expanding the phenotypic spectrum of this disorder. In addition to the characteristic cleft palate, ASD, and persistent superior vena cava, he had low‐set and posteriorly angulated ears, upslanting palpebral fissures, cryptorchidism, and structural brain abnormalities including partial agenesis of the corpus callosum, dysplastic enlarged caudate, and cerebellar hypoplasia with megacisterna magna. Preterm delivery, suspected pulmonary hypoplasia, and pulmonary hypertension resulted in chronic lung disease. At the age of

Significant overlap and possible identity of macrocephaly capillary malformation and megalencephaly polymicrogyria-polydactyly hydrocephalus syndromes.

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Cardiac anomalies in Axenfeld–Rieger syndrome due to a novel FOXC1 mutation

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Neurocognitive, Adaptive, and Behavioral Functioning of Individuals With Costello Syndrome: A Review

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Longitudinal course of cognitive, adaptive, and behavioral characteristics in Costello syndrome†

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Assessing genotype-phenotype correlation in Costello syndrome using a severity score

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