The clinical value of optical genome mapping in the rapid characterization of RB1 duplication and 15q23q24.2 triplication, for more appropriate prenatal genetic counselling.

BACKGROUND: Despite recent advances in prenatal genetic diagnosis, medical geneticists still face considerable difficulty in interpreting the clinical outcome of copy-number-variant duplications and defining the mechanisms underlying the formation of certain chromosomal rearrangements. Optical genome mapping (OGM) is an emerging cytogenomic tool with proved ability to identify the full spectrum of cytogenetic aberrations. METHODS: Here, we report on the use of OGM in a prenatal diagnosis setting. Detailed breakpoint mapping was used to determine the relative orientations of triplicated and duplicated segments in two unrelated foetuses harbouring chromosomal aberrations: a de novo 15q23q24.2 triplication and a paternally inherited 13q14.2 duplication that overlapped partially with the RB1 gene. RESULTS: OGM enabled us to suggest a plausible mechanism for the triplication and confirmed that the RB1 duplication was direct oriented and in tandem. This enabled us to predict the pathogenic consequences, refine the prognosis and adapt the follow-up and familial screening appropriately. CONCLUSION: Along with an increase in diagnostic rates, OGM can rapidly highlight genotype-phenotype correlations, improve genetic counselling and significantly influence prenatal management.

Prenatal Diagnosis of Primrose Syndrome.

Primrose syndrome is a very rare congenital malformation. Symptoms of this disorder may appear during childhood, but the diagnosis is identified in adulthood in the majority of cases. The prenatal diagnosis of Primrose syndrome is not developed in the literature. We present herein a case series of 3 cases with characteristic sonographic features. A dysmorphic metopic suture, downslanting palpebral fissures, a wide forehead, and agenesis of corpus callosum are the main signs. A missense mutation in ZBTB20 identified in whole exome sequencing can confirm the prenatal diagnosis of Primrose syndrome.

Toward clinical and molecular dissection of frontonasal dysplasia with facial skin polyps: From Pai syndrome to differential diagnosis through a series of 27 patients.

Unique or multiple congenital facial skin polyps are features of several rare syndromes, from the most well-known Pai syndrome (PS), to the less recognized oculoauriculofrontonasal syndrome (OAFNS), encephalocraniocutaneous lipomatosis (ECCL), or Sakoda complex (SC). We set up a research project aiming to identify the molecular bases of PS. We reviewed 27 individuals presenting with a syndromic frontonasal polyp and initially referred for PS. Based on strict clinical classification criteria, we could confirm only nine (33%) typical and two (7%) atypical PS individuals. The remaining ones were either OAFNS (11/27-41%) or presenting with an overlapping syndrome (5/27-19%). Because of the phenotypic overlap between these entities, OAFNS, ECCL, and SC can be either considered as differential diagnosis of PS or part of the same spectrum. Exome and/or genome sequencing from blood DNA in 12 patients and from affected tissue in one patient failed to identify any replication in candidate genes. Taken together, our data suggest that conventional approaches routinely utilized for the identification of molecular etiologies responsible for Mendelian disorders are inconclusive. Future studies on affected tissues and multiomics studies will thus be required in order to address either the contribution of mosaic or noncoding variation in these diseases.

Clinical and neuroimaging findings in 33 patients with MCAP syndrome: A survey to evaluate relevant endpoints for future clinical trials.

Megalencephaly-CApillary malformation-Polymicrogyria (MCAP) syndrome results from somatic mosaic gain-of-function variants in PIK3CA. Main features are macrocephaly, somatic overgrowth, cutaneous vascular malformations, connective tissue dysplasia, neurodevelopmental delay, and brain anomalies. The objectives of this study were to describe the clinical and radiological features of MCAP, to suggest relevant clinical endpoints applicable in future trials of targeted drug therapy. Based on a French collaboration, we collected clinical features of 33 patients (21 females, 12 males, median age of 9.9 years) with MCAP carrying mosaic PIK3CA pathogenic variants. MRI images were reviewed for 21 patients. The main clinical features reported were macrocephaly at birth (20/31), postnatal macrocephaly (31/32), body/facial asymmetry (21/33), cutaneous capillary malformations (naevus flammeus 28/33, cutis marmorata 17/33). Intellectual disability was present in 15 patients. Among the MRI images reviewed, the neuroimaging findings were megalencephaly (20/21), thickening of corpus callosum (16/21), Chiari malformation (12/21), ventriculomegaly/hydrocephaly (10/21), cerebral asymmetry (6/21) and polymicrogyria (2/21). This study confirms the main known clinical features that defines MCAP syndrome. Taking into account the phenotypic heterogeneity in MCAP patients, in the context of emerging clinical trials, we suggest that patients should be evaluated based on the main neurocognitive expression on each patient.

Mutations in DDHD1, encoding a phospholipase A1, is a novel cause of retinopathy and neurodegeneration with brain iron accumulation.

Defects of phospholipids remodelling and synthesis are inborn errors of metabolism responsible for various clinical presentations including spastic paraplegia, retinopathy, optic atrophy, myo- and cardiomyopathies, and osteo-cutaneous manifestations. DDHD1 encodes a phospholipase A1, which is involved in the remodelling of phospholipids. We previously described a relatively pure hereditary spastic paraplegia (HSP) phenotype associated with mutations in DDHD1. Here we report a complex form of HSP associated with retinal dystrophy and a pattern of neurodegeneration with brain iron accumulation (NBIA) on brain MRI, due to a novel homozygous mutation in DDHD1. This observation enlarges the clinical spectrum of DDHD1-associated disorders and sheds light on a new aetiology for syndromes associating retinopathy and NBIA. It also emphasizes the role of complex lipids in the retina.

Relapsing encephalopathy with cerebellar ataxia related to an ATP1A3 mutation.

ATP1A3, the gene encoding the α3-subunit of the Na(+) /K(+) -ATPase pump, has been involved in four clinical neurological entities: (1) alternating hemiplegia of childhood (AHC); (2) rapid-onset dystonia parkinsonism (RDP); (3) CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss) syndrome; and (4) early infantile epileptic encephalopathy. Here, we report on a 34-year-old female presenting with a new ATP1A3-related entity involving a relapsing encephalopathy characterized by recurrent episodes of cerebellar ataxia and altered consciousness during febrile illnesses. The term RECA is suggested - relapsing encephalopathy with cerebellar ataxia. The phenotype of this patient, resembling mitochondrial oxidative phosphorylation defects, emphasizes the possible role of brain energy deficiency in patients with ATP1A3 mutations. Rather than multiple overlapping syndromes, ATP1A3-related disorders might be seen as a phenotypic continuum.