Expanding the phenotype spectrum associated with pathogenic variants in the COL2A1 and COL11A1 genes.

We report the clinical findings of 26 individuals from 16 unrelated families carrying variants in the COL2A1 or COL11A1 genes. Using Sanger and next-generation sequencing, 11 different COL2A1 variants (seven novel), were identified in 13 families (19 affected individuals), all diagnosed with Stickler syndrome (STL) type 1. In nine families, the COL2A1 disease-causing variant arose de novo. Phenotypically, we observed myopia (95%) and retinal detachment (47%), joint hyperflexibility (92%), midface retrusion (84%), cleft palate (53%), and various degrees of hearing impairment (50%). One patient had a splenic artery aneurysm. One affected individual carrying pathogenic variant in COL2A1 showed no ocular signs including no evidence of membranous vitreous anomaly. In three families (seven affected individuals), three novel COL11A1 variants were found. The propositus with a de novo variant showed an ultrarare Marshall/STL overlap. In the second family, the only common clinical sign was postlingual progressive sensorineural hearing impairment (DFNA37). Affected individuals from the third family had typical STL2 signs. The spectrum of disease phenotypes associated with COL2A1 or COL11A1 variants continues to expand and includes typical STL and various bone dysplasias, but also nonsyndromic hearing impairment, isolated myopia with or without retinal detachment, and STL phenotype without clinically detectable ocular pathology.

A novel heterozygous RIT1 mutation in a patient with Noonan syndrome, leukopenia, and transient myeloproliferation-a review of the literature.

UNLABELLED: Noonan syndrome (NS) is a genetic condition presenting with typical facies, cardiac defects, short stature, variable developmental deficit, cryptorchidism, skeletal, and other abnormalities. Germline mutations in genes involved in the RAS/MAPK signaling have been discovered to underlie NS. Recently, missense mutations in RIT1 have been reported as causative for individuals with clinical signs of NS. We report on a 2.5-year-old boy with NS phenotype with a novel heterozygous change in the RIT1 gene. The patient was born prematurely from pregnancy monitored for polyhydramnios. At 7 months of age, non-immune neutropenia and splenomegaly have been observed. During the severe pneumonia at 10 months, significant progression of hepatosplenomegaly, leukopenia with monocytosis (15-29 %), and thrombocytopenia occurred. Bone marrow evaluation showed myeloid hyperplasia and monocytosis, suggestive of myeloproliferative syndrome. Clinical phenotype (facial dysmorphism, soft hair, short neck, broad chest, widely spaced nipples, mild pectus carinatum, deep palmar creases, unilateral cryptorchidism), and moderate pulmonary valve stenosis with mild psychomotor delay were indicative of NS. DNA analysis identified a de novo heterozygous variant c.69A >T, p.(Lys23Asn) in exon 2 of the RIT1 gene, presumed to be causative. CONCLUSION: We present a patient with a clinical suspicion of NS carrying a novel substitution in RIT1 and hematologic findings not being observed in RIT1 positive patients to date. Thus, the case broadens variability of hematologic symptoms in RIT1 positive NS individuals. WHAT IS KNOWN: • Noonan syndrome is a common genetically heterogeneous disorder of autosomal dominant inheritance characterized by craniofacial dysmorphism, short stature, congenital heart defects, variable cognitive deficit, and other anomalies. What is new: • We report on a 2.5-year-old male patient with clinical signs of NS and hematologic abnormalities, in whom a novel heterozygous substitution in RIT1 with probable pathogenicity was detected.

Identification of a patient with intellectual disability and de novo 3.7 Mb deletion supports the existence of a novel microdeletion syndrome in 2p14-p15.

Microdeletions spanning 2p14-p15 have recently been described in two patients with developmental and speech delay and intellectual disability but no congenital malformations or severe facial dysmorphism. We report a 4-year-old boy with a de novo 3.7 Mb long deletion encompassing the region deleted in the previous cases. The patient had clinical features partly consistent with the published cases including intellectual disability, absent speech, microcephaly, long face, bulbous nasal tip and thin upper lip, but his overall clinical picture was more severe compared to the published patients. The identification of this additional patient and a detailed analysis of deletions identified in various patient cohorts and in normal individuals support the existence of a new rare microdeletion syndrome in 2p14-p15. Its critical region is in the vicinity of but clearly separate from the minimal region deleted in the well established 2p15-p16.1 microdeletion syndrome. A thorough comparison of the deletions and phenotypes indicates that multiple genes located in this region may be involved in intellectual functioning, and that some patients may show composite and more complex phenotypes due to deletions spanning both critical regions.

Array comparative genome hybridization in patients with developmental delay: two example cases.

Developmental delay is often a predictor of mental retardation (MR) or autism, two relatively frequent developmental disorders severely affecting intellectual and social functioning. The causes of these conditions remain unknown in most patients. They have a strong genetic component, but the specific genetic defects can only be identified in a fraction of patients. Recent developments in genomics supported the establishment of the causal link between copy number variants in the genomes of some patients and their affection. One of the techniques suitable for this analysis is array comparative genome hybridization, which can be used both for detailed mapping of chromosome rearrangements identified by classical cytogenetics and for the identification of novel submicroscopic gains or losses of genetic material. We illustrate the power of this approach in two patients. Patient 1 had a cytogenetically visible deletion of chromosome X and the molecular analysis was used to specify the gene content of the deletion and the prognosis of the child. Patient 2 had a seemingly normal karyotype and the analysis revealed a small recurrent deletion of chromosome 1 likely to be responsible for his phenotype. However, the genetic dissection of MR and autism is complicated by high heterogeneity of the genetic aberrations among patients and by broad variability of phenotypic effects of individual genetic defects.