ORIGINAL RESEARCH ARTICLEPurpose: Mowat-Wilson syndrome (MWS) is a rare intellectual disability/multiple congenital anomalies syndrome caused by heterozygous mutation of the ZEB2 gene. It is generally underestimated because its rarity and phenotypic variability sometimes make it difficult to recognize. Here, we aimed to better delineate the phenotype, natural history, and genotype-phenotype correlations of MWS. Methods:In a collaborative study, we analyzed clinical data for 87 patients with molecularly confirmed diagnosis. We described the prevalence of all clinical aspects, including attainment of neurodevelopmental milestones, and compared the data with the various types of underlying ZEB2 pathogenic variations.Results: All anthropometric, somatic, and behavioral features reported here outline a variable but highly consistent phenotype. By presenting the most comprehensive evaluation of MWS to date, we define its clinical evolution occurring with age and derive suggestions for patient management. Furthermore, we observe that its severity correlates with the kind of ZEB2 variation involved, ranging from ZEB2 locus deletions, associated with severe phenotypes, to rare nonmissense intragenic mutations predicted to preserve some ZEB2 protein functionality, accompanying milder clinical presentations. Conclusion:Knowledge of the phenotypic spectrum of MWS and its correlation with the genotype will improve its detection rate and the prediction of its features, thus improving patient care.

We report on a clinical-genetic study of 16 Wolf-Hirschhorn syndrome (WHS) patients. Hemizygosity of 4p16.3 was detected by conventional prometaphase chromosome analysis (11 patients) or by molecular probes on apparently normal chromosomes (4 patients). One patient had normal chromosomes without a detectable molecular deletion within the WHS "critical region." In each deleted patient, the deletion was demonstrated to be terminal by fluorescence in situ hybridization (FISH). The proximal breakpoint of the rearrangement was established by prometaphase chromosome analysis in cases with a visible deletion. It was within the 4p16.1 band in six patients, apparently coincident with the distal half of this band in five patients. The extent of each of the four submicroscopic deletions was established by FISH analyses with a set of overlapping cosmid clones spanning the 4p16.3 region. We found ample variations in both the size of the deletions and the position of the respective breakpoints. The precise definition of the cytogenetic defect permitted an analysis of the genotype-phenotype correlations in WHS, leading to the proposal of a set of minimal diagnostic criteria, which in turn may facilitate the selection of critical patients in the search for the gene(s) responsible for this disorder. We observed that genotype-phenotype correlations in WHS mostly depend on the size of the deletion, a deletion of <3.5 Mb resulting in a mild phenotype, in which malformations are absent. The absence of a detectable molecular deletion is still consistent with a WHS diagnosis. Based on these observations a "minimal" WHS phenotype was inferred, the clinical manifestations of which are restricted to the typical facial appearance, mild mental and growth retardation, and congenital hypotonia.

Pitt-Hopkins syndrome (PTHS) is characterized by severe intellectual disability, typical facial gestalt and additional features, such as breathing anomalies. Following the discovery of the causative haploinsufficiency of transcription factor 4 (TCF4), about 60 patients have been reported. We looked for TCF4 mutations in 63 patients with a suspected PTHS. Haploinsufficiency of TCF4 was identified in 14 patients, as a consequence of large 18q21.2 chromosome deletions involving TCF4 (2 patients), gene mutations (11 patients) and a t(14q;18q) balanced translocation disrupting TCF4 (one patient). By evaluating the clinical features of these patients, along with literature data, we noticed that, in addition to the typical facial gestalt, the PTHS phenotype results from the various combinations of the following characteristics: intellectual disability with severe speech impairment, normal growth parameters at birth, postnatal microcephaly, breathing anomalies, motor incoordination, ocular anomalies, constipation, seizures, typical behavior and subtle brain abnormalities. Although PTHS is currently considered to be involved in differential diagnosis with Angelman and Rett syndromes, we found that combining the facial characteristics with a detailed analysis of both the physical and the neurological phenotype, made molecular testing for PTHS the first choice. Based on striking clinical criteria, a diagnosis of PTHS was made clinically in two patients who had normal TCF4. This report deals with the first series of PTHS patients of Italian origin.

Untreated classic galactosemia (galactose-1-phosphate uridyltransferase [GALT] deficiency) is known as a secondary congenital disorders of glycosylation (CDG) characterized by galactose deficiency of glycoproteins and glycolipids (processing defect or CDG-II). The mechanism of this undergalactosylation has not been established. Here we show that in untreated galactosemia, there is also a partial deficiency of whole glycans of serum transferrin associated with increased fucosylation and branching as seen in genetic glycosylation assembly defects (CDG-I). Thus galactosemia seems to be a secondary "dual" CDG causing a processing as well as an assembly N-glycosylation defect. We also demonstrated that in galactosemia patients, transferrin N-glycan biosynthesis is restored upon dietary treatment.