Gerarda Cappuccio

Clinical description of a patient carrying the smallest reported deletion involving 10p14 region

Haploinsufficiency of a region located distal to 10p14 designated HDR1, is responsible for hypoparathyroidism, sensorineural deafness, and renal anomalies (HDR syndrome). Haploinsufficiency of a more proximal region, located on 10p13‐10p14, designated as DGCR2 is associated with congenital heart defects and thymus hypoplasia/aplasia or T cell defect. We describe a patient showing facial dysmorphisms, delayed psychomotor development and bilateral sensorineural hearing loss and carrying a 10p14 deletion, the smallest deletion found in the literature so far. Our patient, carrying a partial deletion of the DGCR2 region and of the HDR1 region, including the GATA3 gene, showed, unexpectedly, only few of the clinical features of DiGeorge 2 syndrome (psychomotor retardation, palpebral ptosis, epicanthic folds, anteverted nares, cryptorchidism, hand/foot abnormalities) and did not show other typical signs, such as cardiac defect, cleft palate, and abnormal T cell levels. Of the three characteristic features of the HDR syndrome, our patient had only sensorineural deafness. On the basis of the revision of the other cases reported in the literature with a deletion including the 10p14 region, we suggest that GATA3 haploinsufficiency, although not recorded for each patient, is responsible for deafness. The present case shows that even this small 10p deletion is responsible for a specific phenotype. We also underline the importance of CGH‐array, in order to obtain a more precise physical mapping of the 10p deletions and an accurate genotype–phenotype correlation.

Mental Retardation, Congenital Heart Malformation, and Myelodysplasia in a Patient With a Complex Chromosomal Rearrangement Involving the Critical Region 21q22

The region 21q22 is considered crucial for the pathogenesis of both Down syndrome (DS) and the partial monosomy 21q syndrome. Haploinsufficiency of the RUNX‐1 gene, mapping at 21q22 is responsible for a platelet disorder and causes predisposition to myelodysplastic syndrome (MDS). We describe a 3‐year‐old girl with mental retardation, congenital heart malformation, and subtle dysmorphic facial features. The patient developed thrombocytopenia when she was 2 years old. Bone marrow smear led to the diagnosis of myelodysplasia. Prenatal karyotyping had shown chromosome 21 pericentric inversion. Postnatally the array‐CGH revealed duplication at bands 21q11.2–21q21.1 and a simultaneous deletion involving the region 21q22.13–21q22.3. RUNX‐1 mRNA levels analyzed in patients skin fibroblasts were reduced. In this child the monosomy of the region 21q22 likely had the main role in determining the phenotype. Although the RUNX‐1 gene is localized outside the deleted region, we speculate that RUNX‐1 reduced expression, is probably due to the deletion of regulatory factors and caused the hematologic disorder in the patient. The present report underlines also the importance of array‐CGH in characterizing patients with a complex phenotype.

Diagnosis of adenylosuccinate lyase deficiency by metabolomic profiling in plasma reveals a phenotypic spectrum.

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive neurometabolic disorder that presents with a broad-spectrum of neurological and physiological symptoms. The ADSL gene produces an enzyme with binary molecular roles in de novo purine synthesis and purine nucleotide recycling. The biochemical phenotype of ADSL deficiency, accumulation of SAICAr and succinyladenosine (S-Ado) in biofluids of affected individuals, serves as the traditional target for diagnosis with targeted quantitative urine purine analysis employed as the predominate method of detection. In this study, we report the diagnosis of ADSL deficiency using an alternative method, untargeted metabolomic profiling, an analytical scheme capable of generating semi-quantitative z-score values for over 1000 unique compounds in a single analysis of a specimen. Using this method to analyze plasma, we diagnosed ADSL deficiency in four patients and confirmed these findings with targeted quantitative biochemical analysis and molecular genetic testing. ADSL deficiency is part of a large a group of neurometabolic disorders, with a wide range of severity and sharing a broad differential diagnosis. This phenotypic similarity among these many inborn errors of metabolism (IEMs) has classically stood as a hurdle in their initial diagnosis and subsequent treatment. The findings presented here demonstrate the clinical utility of metabolomic profiling in the diagnosis of ADSL deficiency and highlights the potential of this technology in the diagnostic evaluation of individuals with neurologic phenotypes.

A case of 14q11.2 microdeletion with autistic features, severe obesity and facial dysmorphisms suggestive of Wolf–Hirschhorn syndrome

We report on a 21‐year old woman with intellectual disability, autistic features, severe obesity, and facial dysmorphisms suggestive of Wolf–Hirschhorn syndrome (WHS). Array‐CGH analysis showed a 2.89 Mb deletion on chromosome 14q11.2 containing 47 known genes. The most interesting genes included in this deletion are CHD8, a chromodomain helicase DNA binding protein that is associated with autism spectrum disorders, and MMP14, a matrix metalloproteinase that has been linked to obesity and type 2 diabetes. This report shows that 14q11.2 microdeletions can mimic WHS and suggests that gene(s) in the deleted interval that may be responsible for a phenocopy of WHS.

Loeys–Dietz syndrome type 4, caused by chromothripsis, involving the TGFB2 gene

The TGF-β signaling pathway controls cellular proliferation, growth and differentiation and regulates several functions of the connective tissue. Disruption of genes coding for components of the TGF-β signaling pathway or its interactors, such as fibrillin-1, has been shown to cause several human pathologies. Large deletions and non-sense mutations in TGFB2 gene have been recently described in patients with aortic aneurysm, scoliosis, arachnodactyly, chest deformities, joint hyper-flexibility, and mild intellectual disability; this condition has been called Loeys-Dietz syndrome, type 4. In this paper we describe an 18-year-old girl with borderline mental impairment, seizures, retinal degeneration, short stature, congenital hip dysplasia, severe and worsening joint hypermobility, scoliosis, progressive deformation of the long bones, aortic dilatation and platelet disorder. Molecular study of DNA by Array-CGH demonstrated four de novo microdeletions: TGFB2 is among the genes deleted and we consider it the obvious candidate for the clinical phenotype. The multiple chromosomal rearrangements detected in the current patient can be ascribed to an event of constitutional chromothripsis.

Bronchial isomerism in a Kabuki syndrome patient with a novel mutation in MLL2 gene

BackgroundKabuki syndrome (KS) is a rare, multiple congenital anomalies/intellectual disability syndrome caused by mutations of MLL2 gene, which codifies for a histone methyltrasferase that regulates the embryogenesis and the tissue development. Left-bronchial isomerism is a rare congenital abnormality that can be defined as the absence of the normal lateralizing features which distinguish right and left-sides in the lungs. To date, this is the first report of left-bronchial isomerism in association with KS.Case presentationA one-month-old Caucasian male patient underwent our attention for microcephaly, dysmorphic features (long palpebral fissures, eyebrows with sparse lateral third, everted lower eyelids, blue sclerae, large dysplastic ears, lower lip pits), persistent fetal fingertip pads, short stature, heart defects (interventricular defect and aortic coarctation), unilateral cryptorchidism, hypotonia and delay in gross motor skills. These features suggested a diagnosis of KS and a molecular analysis confirmed a novel frame-shift mutation in the exon 11 of MLL2 gene. Subsequently, given recurrent respiratory infections with a normal immunological status, he underwent a chest CT scan that showed a left bronchial isomerism.ConclusionWe report a patient affected by KS, with a novel MLL2 mutation and an atypical phenotype characterized by left-side bronchial isomerism. Interestingly, genes involved in the heterotaxia/isomerism such as ROCK2 and SHROOM3 are known to interact with MLL2 gene. In order to achieve a correct diagnosis and an appropriate therapy, the presence of pulmonary anatomical variations should be investigated in KS patients with respiratory signs not associated to immunological deficiency. Finally, our findings support the hypothesis that the mutations leading to a complete loss of function of MLL2 gene is often associated with complex visceral malformations.

Cardiac valve disease: an unreported feature in Ehlers Danlos syndrome arthrocalasia type?

Ehlers Danlos syndrome (EDS) athrocalasia type (type VII), is characterized by joint hypermobility, skin hyperextensibility and tissue fragility. No heart involvement has been reported. Two forms have been described: type VII A and VII B. The abnormally processed collagen α2(I) and the skipping of the exon 6 in COL1A2 gene are typically detected in EDS type VII B. We describe a seven-year old female, with a phenotype consistent with EDS type VII B and a diagnosis further confirmed by biochemical and molecular analyses. Cardiac ultrasound showed normal data in the first year of life. When she was 5 years old, the patient developed mitral valve regurgitation, and aortic and tricuspidal insufficiency at 7 years of age. To our knowledge, this is the first report of cardiac valvular involvement in EDS VII B. This feature probably has been underreported for the limited follow-up of the patients. Echocardiography might be warranted in the clinical assessment of EDS VII patients.

Variegated silencing through epigenetic modifications of a large Xq region in a case of balanced X;2 translocation with Incontinentia Pigmenti-like Phenotype

Molecular mechanisms underlying aberrant phenotypes in balanced X;autosome translocations are scarcely understood. We report the case of a de novo reciprocal balanced translocation X;2(q23;q33) presenting phenotypic alterations highly suggestive of Incontinentia Pigmenti (IP) syndrome, a genodermatosis with abnormal skin pigmentation and neurological failure, segregating as X-linked dominant disorder. Through molecular studies, we demonstrated that the altered phenotype could not be ascribed to chromosome microdeletions or to XIST-mediated inactivation of Xq24-qter. Interestingly, we found that the Xq24-qter region, which translocated downstream of the heterochromatic band 2q34, undergoes epigenetic silencing mediated by DNA methylation and histone alterations. Among the downregulated genes, we found the inhibitor of kappa light polypeptide gene enhancer in B cells, kinase gamma (IKBKG/NEMO), the causative gene of IP. We hypothesize that a mosaic functional nullisomy of the translocated genes, through a Position Effect Variegation-like heterochromatization, might be responsible for the proband’s phenotypic anomalies. Partial silencing of IKBKG may be responsible for the skin anomalies observed, thereby mimicking the IP pathological condition. In addition to its clinical relevance, this paper addresses fundamental issues related to the chromatin status and nuclear localization of a human euchromatic region translocated proximally to heterochromatin. In conclusion, the study provides new insight into long-range gene silencing mechanisms and their direct impact in human disease.

De novo PIK3R2 variant causes polymicrogyria, corpus callosum hyperplasia and focal cortical dysplasia

We report an 8-year-old boy with a complex cerebral malformation, intellectual disability, and complex partial seizures. Whole-exome sequencing revealed a yet unreported de novo variant in the PIK3R2 gene that was recently associated with megalencephaly–polymicrogyria–polydactyly–hydrocephalus (MPPH) syndrome and bilateral perisylvian polymicrogyria (BPP). Our patient showed cerebral abnormalities (megalencephaly, perisylvian polymicrogyria, and mega corpus callosum) that were consistent with these conditions. Imaging also showed right temporal anomalies suggestive of cortical dysplasia. Until now, only three variants (c.1117G>A (p.(G373R)), c.1126A>G (p.(K376E)) and c.1202T>C (p.(L401P))) affecting the SH2 domain of the PIK3R2 protein have been reported in MPPH and BPP syndromes. In contrast to the variants reported so far, the patient described herein exhibits the c.1669G>C (p.(D557H)) variant that affects a highly conserved residue at the interface with the PI3K catalytic subunit α. The phenotypic spectrum associated with variants in this gene and its pathway are likely to continue to expand as more cases are identified.

Early onset Charcot-Marie-Tooth neuropathy type 2A and severe developmental delay: expanding the clinical phenotype of MFN2-related neuropathy

Charcot‐Marie‐Tooth (CMT) syndromes are a group of clinically heterogeneous disorders of the peripheral nervous system. Mutations of mitofusin 2 (MFN2) have been recognized to be associated with CMT type 2A (CMT2A). CMT2A is primarily an axonal disorder resulting in motor and sensory neuropathy. We report a male child with psychomotor delay, dysmorphic features, and weakness of lower limbs associated with electrophysiological features of severe, sensory‐motor, axonal neuropathy. The patient was diagnosed with early onset CMT2A and severe psychomotor retardation associated with c.310C>T mutation (p.R104W) in MFN2 gene. CMT2A should be considered in patients with both axonal sensory‐motor neuropathy and developmental delay.