Expanding the phenotype of PIGP deficiency to multiple congenital anomalies-hypotonia-seizures syndrome.

Glycosylphosphatidylinositol-anchored proteins are involved in multiple physiological processes and the initial stage of their biosynthesis is mediated by PIGA, PIGC, PIGH, PIGP, PIGQ, PIGY, and DMP2 genes, which have been linked to a wide spectrum of phenotypes depending on the gene damaged. To date, the PIGP gene has only been related to Developmental and Epileptic Encephalopathy 55 (MIM#617599) in just seven patients. A detailed medical history was performed in two affected siblings with a multiple malformation syndrome. Genetic testing was performed using whole-exome sequencing. One patient presented dysmorphic features, congenital anomalies, hypotonia and epileptic encephalopathy as described in PIGA, PIGQ and PIGY deficiencies. The other one was a fetus with a severe malformation disorder at 17 weeks of gestation whose pregnancy was interrupted. Both were compound heterozygous of pathogenic variants in PIGP gene: NM_153682.3:c.2 T > C(p.?) and a 136 Kb deletion (GRCh37/hg19 21q22.13(chr21:38329939-38 466 066)×1) affecting the entire PIGP gene. Our results extend the clinical phenotype associated to PIGP gene and propose to include it as a novel cause of Multiple Congenital Anomalies-Hypotonia-Seizures syndrome.

Further characterization of Borjeson-Forssman-Lehmann syndrome in females due to de novo variants in PHF6.

While inherited hemizygous variants in PHF6 cause X-linked recessive Borjeson-Forssman-Lehmann syndrome (BFLS) in males, de novo heterozygous variants in females are associated with an overlapping but distinct phenotype, including moderate to severe intellectual disability, characteristic facial dysmorphism, dental, finger and toe anomalies, and linear skin pigmentation. By personal communication with colleagues, we assembled 11 additional females with BFLS due to variants in PHF6. We confirm the distinct phenotype to include variable intellectual disability, recognizable facial dysmorphism and other anomalies. We observed skewed X-inactivation in blood and streaky skin pigmentation compatible with functional mosaicism. Variants occurred de novo in 10 individuals, of whom one was only mildly affected and transmitted it to her more severely affected daughter. The mutational spectrum comprises a two-exon deletion, five truncating, one splice-site and three missense variants, the latter all located in the PHD2 domain and predicted to severely destabilize the domain structure. This observation supports the hypothesis of more severe variants in females contributing to gender-specific phenotypes in addition to or in combination with effects of X-inactivation and functional mosaicism. Therefore, our findings further delineate the clinical and mutational spectrum of female BFLS and provide further insights into possible genotype-phenotype correlations between females and males.

Mitochondrial developmental encephalopathy with bilateral optic neuropathy related to homozygous variants in IMMT gene.

IMMT gene codes for mitofilin, a mitochondrial inner membrane protein that regulates the morphology of mitochondrial cristae. The phenotype associated with mutations in this gene has not been yet established, but functional studies carried out show that its loss causes a mitochondrial alteration, both in the morphology of the mitochondrial crests and in their function. We present two cousins from an extended highly consanguineous family with developmental encephalopathy, hypotonia, nystagmus due to optic neuropathy. The likely pathogenic homozygous c.895A>G (p.Lys299Glu) variant in the IMMT gene co-segregates with the disease and associates altered mitochondrial cristae observed by electron microscopy.

Leucoencefalopatía megalencefálica con quistes: importancia de la descripción clínica en la era genética / Megalencephalic leukoencephalopathy with cysts -the clinical importance in the genetic era

INTRODUCCIÓN: La leucoencefalopatía megalencefálica con quistes es una leucodistrofia de origen genético que produce una alteración de la homeostasis del agua e iones en el cerebro, generando formas vacuolares y edema crónico en la sustancia blanca con deterioro neurológico progresivo. Debe sospecharse en los lactantes que presentan macrocefalia progresiva durante el primer año de vida, retraso motor y hallazgos característicos en la resonancia magnética cerebral. CASO CLÍNICO: Niña en seguimiento desde los 9 meses por macrocefalia progresiva y retraso del desarrollo psicomotor con presencia en la resonancia magnética cerebral de hallazgos compatibles con leucoencefalopatía megalencefálica con quistes, y aparición de epilepsia en su evolución. Los estudios genéticos habituales (secuenciación de nueva generación y array) fueron negativos, pero, al cumplir los criterios diagnósticos, se procedió al estudio del ARN mensajero y el ADN complementario, que confirmó la presencia de dos variantes patogénicas en MLC1. CONCLUSIONES: La leucoencefalopatía megalencefálica con quistes es una entidad infrecuente. Es característica la macrocefalia progresiva en el primer año de vida, la ausencia de deterioro o deterioro lento, y la posibilidad de desarrollar epilepsia, espasticidad y ataxia en su evolución. Cobra importancia en dichos pacientes la realización de una prueba de imagen que muestre hallazgos propios de la entidad, lo que, junto con la clínica, permite diferenciarla de otras leucodistrofias y establecer un diagnóstico confirmatorio. Los estudios genéticos pueden constatar la mutación asociada que posibilita predecir el fenotipo clinicorradiológico

INTRODUCTION: Megalencephalic leukoencephalopathy with cysts is a leukodystrophy of genetic origin that produces an alteration in the water and ion homeostasis in the brain, generating vacuolar forms and chronic oedema in the white matter with progressive neurological deterioration. It should be suspected in infants who present progressive macrocephaly during the first year of life, motor retardation and characteristic findings in magnetic resonance brain scans. CASE REPORT: We report the case of a girl who was followed up from the age of 9 months due to progressive macrocephaly and delayed psychomotor development and brain MRI findings consistent with megalencephalic leukoencephalopathy with cysts, and the appearance of epilepsy during its development. The usual genetic studies (new generation sequencing and array) were negative, but as the diagnostic criteria were met, a complementary messenger RNA and DNA study was conducted, which confirmed the presence of two pathogenic variants in MLC1. CONCLUSIONS: Megalencephalic leukoencephalopathy with cysts is a rare condition. Progressive macrocephaly in the first year of life, the absence of deterioration or slow deterioration, and the possibility of developing epilepsy, spasticity and ataxia are characteristic signs in its course. It is important for these patients to undergo an imaging test that shows findings that characterise this condition, which, together with the clinical features, makes it possible to differentiate it from other leukodystrophies and to establish a confirmatory diagnosis. Genetic studies can confirm the associated mutation that makes it possible to predict the clinicoradiological phenotype

Mutations in PMM2 gene in four unrelated Spanish families with polycystic kidney disease and hyperinsulinemic hypoglycemia.

Objectives Hyperinsulinemic hypoglucemia (HH) is characterized by a dysregulation of insulin secretion from pancreatic ß cells. Congenital hyperinsulinism has been associated with specific genes in monogenic forms and also with other diseases with a yet unknown genetic cause. In 2017, Rubio Cabezas et al. described the association of HH and autosomal recessive polycystic kidney disease (ARPKD) with a promoter mutation in the PMM2 gene. They found that all the patients carried a promoter mutation (c-167G>T) in PMM2, either homozygous or in trans with a second PMM2 coding mutation. Methods We performed the study of the PMM2 gene in six patients from four unrelated families, previously diagnosed with ARPKD and HH. Results All these patients had in common the heterozygous variant c-167G>T in the promoter region for PMM2. Additionally, each patient carried a compound heterozygote for a second missense mutation in this gene (p.Arg141His, p.Asp148Asn or p.Phe157Ser), previously reported as pathogenic for congenital disorder of glycosylation type Ia, with an autosomal recessive inheritance pattern. Unlike the previous published article, two of our patients showed altered type 1 pattern and one of them with rectal bleeding that could be a sign of PMM2-congenital disorders of glycosylation. Conclusion We propose the study of this gene when carrying out the diagnosis of patients with HH, especially in the neonatal period and when a recessive polycystic kidney disease without alterations in PKDH1 is diagnosed.

Prenatal diagnosis of a female fetus with ring chromosome 9, 46,XX,r(9)(p24q34), and a de novo interstitial 9p deletion.

Ring chromosomes are circular structures formed as a result of breaks in the chromosome arms and the fusion of the proximal broken ends with a loss of distal material, or by fusion of dysfunctional telomeres without any loss. The mechanism underlying this process has not yet been sufficiently explained. Commonly, rings occur as acquired genetic abnormalities; however, sometimes they are found as constitutional aberrations with a prevalence of around 1:50,000 live births. Here, we present a new case of r(9) in a female fetus with intrauterine growth retardation and slight craniofacial dysmorphisms. Both parents had a normal phenotype. Amniotic fluid karyotype showed r(9)(p24q34). An array CGH revealed 3 deletion segments: a ring chromosome with a 2.57-Mb deletion at 9pterp24.2 (chr9:163,131-2,729,722), a 2.60-Mb deletion at 9q34.3qter (chr9:138,523,302-141,122,055), and also a 0.15-Mb interstitial deletion at 9p24.1 (chr9:5,090,443-5,235,765). These deletions overlap with proposed regions for the 9p24.3 deletion and Kleefstra syndrome. Segregation analysis revealed a maternal origin of the rearranged chromosome. We conclude that both the ring chromosome and the interstitial deletion occurred de novo. This last deletion has not been reported before. Prenatal array CGH, combined with fine mapping of breakpoints contributes to the assessment of genotype-phenotype correlations.