Elizabeth A. Sellars

Clinical delineation and natural history of the PIK3CA -related overgrowth spectrum

Somatic mutations in the phosphatidylinositol/AKT/mTOR pathway cause segmental overgrowth disorders. Diagnostic descriptors associated with PIK3CA mutations include fibroadipose overgrowth (FAO), Hemihyperplasia multiple Lipomatosis (HHML), Congenital Lipomatous Overgrowth, Vascular malformations, Epidermal nevi, Scoliosis/skeletal and spinal (CLOVES) syndrome, macrodactyly, and the megalencephaly syndrome, Megalencephaly‐Capillary malformation (MCAP) syndrome. We set out to refine the understanding of the clinical spectrum and natural history of these phenotypes, and now describe 35 patients with segmental overgrowth and somatic PIK3CA mutations. The phenotypic data show that these previously described disease entities have considerable overlap, and represent a spectrum. While this spectrum overlaps with Proteus syndrome (sporadic, mosaic, and progressive) it can be distinguished by the absence of cerebriform connective tissue nevi and a distinct natural history. Vascular malformations were found in 15/35 (43%) and epidermal nevi in 4/35 (11%) patients, lower than in Proteus syndrome. Unlike Proteus syndrome, 31/35 (89%) patients with PIK3CA mutations had congenital overgrowth, and in 35/35 patients this was asymmetric and disproportionate. Overgrowth was mild with little postnatal progression in most, while in others it was severe and progressive requiring multiple surgeries. Novel findings include: adipose dysregulation present in all patients, unilateral overgrowth that is predominantly left‐sided, overgrowth that affects the lower extremities more than the upper extremities and progresses in a distal to proximal pattern, and in the most severely affected patients is associated with marked paucity of adipose tissue in unaffected areas. While the current data are consistent with some genotype–phenotype correlation, this cannot yet be confirmed.

The H19 Differentially Methylated Region Marks the Parental Origin of a Heterologous Locus without Gametic DNA Methylation

ABSTRACT Igf2 and H19 are coordinately regulated imprinted genes physically linked on the distal end of mouse chromosome 7. Genetic analyses demonstrate that the differentially methylated region (DMR) upstream of the H19 gene is necessary for three distinct functions: transcriptional insulation of the maternal Igf2 allele, transcriptional silencing of paternal H19 allele, and marking of the parental origin of the two chromosomes. To test the sufficiency of the DMR for the third function, we inserted DMR at two heterologous positions in the genome, downstream of H19 and at the alpha-fetoprotein locus on chromosome 5. Our results demonstrate that the DMR alone is sufficient to act as a mark of parental origin. Moreover, this activity is not dependent on germ line differences in DMR methylation. Thus, the DMR can mark its parental origin by a mechanism independent of its own DNA methylation.

Further supporting evidence for the SATB2‐associated syndrome found through whole exome sequencing

The SATB2‐associated syndrome (SAS) was recently proposed as a clinically recognizable syndrome that results from deleterious alterations of the SATB2 gene in humans. Although interstitial deletions at 2q33 encompassing SATB2, either alone or contiguously with other genes, have been reported before, there is limited literature regarding intragenic mutations of this gene and the resulting phenotype. We describe five patients in whom whole exome sequencing identified five unique de novo mutations in the SATB2 gene (one splice site, one frameshift, and three nonsense mutations). The five patients had overlapping features that support the characteristic features of the SAS: intellectual disability with limited speech development and craniofacial abnormalities including cleft palate, dysmorphic features, and dental abnormalities. Furthermore, Patient 1 also had features not previously described that represent an expansion of the phenotype. Osteopenia was seen in two of the patients, suggesting that this finding could be added to the list of distinctive findings. We provide supporting evidence that analysis for deletions or point mutations in SATB2 should be considered in children with intellectual disability and severely impaired speech, cleft or high palate, teeth abnormalities, and osteopenia.

Cardiovascular and genitourinary anomalies in patients with duplications within the Williams syndrome critical region: phenotypic expansion and review of the literature.

Williams syndrome results from a microdeletion of approximately 1.5 Mb of chromosome 7q11.23. Several patients have been reported with the reciprocal microduplication in association with a variety of phenotypic features including cognitive impairment and typical facial features, though only a few have had birth defects. We report on three probands with duplications within 7q11.23 of variable sizes; two with cardiovascular involvement including aortic dilation and the other with unilateral renal and gonadal agenesis. We offer a comparison with previously reported cases of duplications of 7q11.23. In light of the present cases, we recommend undertaking echocardiographic and renal ultrasound evaluation of patients with documented 7q11.23 duplications. Further, this cytogenetic abnormality should be part of the differential diagnosis for patients with aortic dilation, as well as those with unilateral renal and gonadal agenesis.

Ventricular noncompaction and absent thumbs in a newborn with tetrasomy 5q35.2-5q35.3: an association with Hunter-McAlpine syndrome?

We report on an infant with tetrasomy of 5q35.2‐5q35.3, an interstitial triplication on one chromosome and normal complement on the other. The patient has some features of Hunter–McAlpine syndrome including intrauterine growth retardation (IUGR), almond‐shaped eyes, epicanthal folds, and downturned mouth with thin vermillion of the upper lip. In addition, left ventricular noncompaction and absent thumbs were identified, which have never been described in Hunter–McAlpine syndrome. This chromosome abnormality is distinct from those previously reported. Within this region of tetrasomy is MSX2, a highly conserved homeobox containing gene. Increased copies of MSX2 have been previously associated with craniosynostosis. Our patients only skeletal defect is absent thumbs, also potentially related to increased dosage of MSX2 which is important for limb formation. In addition, MSX2 is expressed in the developing heart and overexpression of this gene may disrupt the co‐regulation of other cardiac genes in this region, namely CSX1.

A Newborn With Complex Skeletal Abnormalities, Joint Contractures, and Bilateral Corneal Clouding With Sclerocornea

A newborn presented to genetics with complex skeletal abnormalities, joint contractures, and bilateral corneal clouding with sclerocornea. The patient survived for 8 months before succumbing to respiratory failure. Exome sequencing revealed a compound heterozygous mutation in theB3GALT6gene. Mutations in this gene have been associated with both Ehlers- Danlos syndrome, progeroid type 2 and spondyloepimetaphyseal dysplasia with joint laxity type 1. These diagnoses encompass the skeletal and joint findings. Our patient expands the phenotype of these diagnoses, as anterior segment eye anomalies have not been described with either syndrome, and he is much more profoundly affected. Interestingly, our patient fits the description of a rare genetic disease referred to as Al-Gazali syndrome, for which the genetic cause is unknown.

Outcomes of four patients with homocysteine remethylation disorders detected by newborn screening

Purpose:We evaluated the clinical outcome in homocysteine remethylation disorders following newborn screening (NBS) and initiation of early specific treatment.Methods:Five patients with remethylation disorders were included in this study.Results:Two asymptomatic patients (one with cblG and one with cblE) were identified by NBS using an approach that combines a postanalytical interpretive tool (available on the Region 4 Stork (R4S) collaborative project website, http://www.clir-r4s.org) and a second-tier test for total homocysteine determination. Both the initial screening and the second-tier test are performed on the same blood spot, with no additional patient contact, resulting in no false-positive outcomes. Two additional patients with methylenetetrahydrofolate reductase deficiency were detected by NBS using low methionine as a marker. Although already symptomatic despite the early diagnosis, the latter two patients greatly improved with treatment and their outcomes are compared with that of another patient with methylenetetrahydrofolate reductase deficiency and significant morbidity who was diagnosed clinically at 3 months of age.Conclusion:Early detection by NBS and timely and specific treatment considerably improve at least short-term outcomes of homocysteine remethylation disorders. When a remethylation disorder is suspected, group-specific treatment could be started prior to the completion of in vitro confirmatory testing because all disorders from this group require similar intervention.Genet Med 18 2, 162–167.

Mutations in INPP5K Cause a Form of Congenital Muscular Dystrophy Overlapping Marinesco-Sjögren Syndrome and Dystroglycanopathy

Congenital muscular dystrophies display a wide phenotypic and genetic heterogeneity. The combination of clinical, biochemical, and molecular genetic findings must be considered to obtain the precise diagnosis and provide appropriate genetic counselling. Here we report five individuals from four families presenting with variable clinical features including muscular dystrophy with a reduction in dystroglycan glycosylation, short stature, intellectual disability, and cataracts, overlapping both the dystroglycanopathies and Marinesco-Sjögren syndrome. Whole-exome sequencing revealed homozygous missense and compound heterozygous mutations in INPP5K in the affected members of each family. INPP5K encodes the inositol polyphosphate-5-phosphatase K, also known as SKIP (skeletal muscle and kidney enriched inositol phosphatase), which is highly expressed in the brain and muscle. INPP5K localizes to both the endoplasmic reticulum and to actin ruffles in the cytoplasm. It has been shown to regulate myoblast differentiation and has also been implicated in protein processing through its interaction with the ER chaperone HSPA5/BiP. We show that morpholino-mediated inpp5k loss of function in the zebrafish results in shortened body axis, microphthalmia with disorganized lens, microcephaly, reduced touch-evoked motility, and highly disorganized myofibers. Altogether these data demonstrate that mutations in INPP5K cause a congenital muscular dystrophy syndrome with short stature, cataracts, and intellectual disability.

Biallelic mutations in the ferredoxin reductase gene cause novel mitochondriopathy with optic atrophy

Abstract Iron–sulfur (Fe-S) clusters are ubiquitous cofactors essential to various cellular processes, including mitochondrial respiration, DNA repair, and iron homeostasis. A steadily increasing number of disorders are being associated with disrupted biogenesis of Fe–S clusters. Here, we conducted whole-exome sequencing of patients with optic atrophy and other neurological signs of mitochondriopathy and identified 17 individuals from 13 unrelated families with recessive mutations in FDXR, encoding the mitochondrial membrane-associated flavoprotein ferrodoxin reductase required for electron transport from NADPH to cytochrome P450. In vitro enzymatic assays in patient fibroblast cells showed deficient ferredoxin NADP reductase activity and mitochondrial dysfunction evidenced by low oxygen consumption rates (OCRs), complex activities, ATP production and increased reactive oxygen species (ROS). Such defects were rescued by overexpression of wild-type FDXR. Moreover, we found that mice carrying a spontaneous mutation allelic to the most common mutation found in patients displayed progressive gait abnormalities and vision loss, in addition to biochemical defects consistent with the major clinical features of the disease. Taken together, these data provide the first demonstration that germline, hypomorphic mutations in FDXR cause a novel mitochondriopathy and optic atrophy in humans.

COL1A1 and COL1A2 sequencing results in cohort of patients undergoing evaluation for potential child abuse

Child abuse is a major public health concern that can explain a proportion of fractures in children. Osteogenesis imperfecta (OI) is the most common inherited syndrome that predisposes to skeletal fractures. We conducted a retrospective analysis of data from clinical, laboratory, and radiographic information from children evaluated for child abuse in which molecular testing for COL1A1 and COL1A2 genes was conducted. A total of 43 patients underwent molecular testing for OI. Pathogenic variants predicted to result in a mild form of OI were found in two patients (5%), both clinically suspected to have this diagnosis. None of the cases in whom OI molecular testing was ordered when maltreatment concerns were thought to be more likely (0/35) were identified to have pathogenic variants. After reviewing each individual case, the final diagnosis was child abuse for 34 cases (77%), and additional radiographic and laboratory studies did not identify any with inherited metabolic predisposition to fracture or rickets. We conclude that routine testing for OI in the setting of child abuse when no other suggestive clinical findings are present has a low yield. A careful review of the medical history and a detailed clinical evaluation help identify those at risk for genetic alterations.