Summary Lysosomal α-galactosidase A (α-Gal) is the enzyme deficient in Fabry disease (FD), an X-linked glycosphingolipidosis caused by pathogenic mutations affecting the GLA gene. The early-onset, multi-systemic FD classical phenotype is associated with absent or severe enzyme deficiency, as measured by in vitro assays, but patients with higher levels of residual α-Gal activity may have later-onset, more organ-restricted clinical presentations. A change in the codon 118 of the wild-type α-Gal sequence, replacing basic arginine by a potentially sulfhydryl-binding cysteine residue – GLA p.(Arg118Cys) –, has been recurrently described in large FD screening studies of high-risk patients. Although the Cys118 allele is associated with high residual α-Gal activity in vitro, it has been classified as a pathogenic mutation, mainly on the basis of theoretical arguments about the chemistry of the cysteine residue. However its pathogenicity has never been convincingly demonstrated by pathology criteria. We reviewed the clinical, biochemical and histopathology data obtained from 22 individuals of Portuguese and Spanish ancestry carrying the Cys118 allele, including 3 homozygous females. Cases were identified either on the differential diagnosis of possible FD manifestations and on case-finding studies (n=11; 4 males), or on unbiased cascade screening of probands’ close relatives (n=11; 3 males). Overall, those data strongly suggest that the GLA p.(Arg118Cys) variant does not segregate with FD clinical phenotypes in a Mendelian fashion, but might be a modulator of the multifactorial risk of cerebrovascular disease, since the allelic frequency in stroke patients was 0.0087 (p=0.0185 vs the general population). The Cys118 allelic frequency in healthy Portuguese adults (n=696) has been estimated as 0.001, therefore not qualifying for “rare” condition.

Haploinsufficiency of AUTS2 has been associated with a syndromic form of neurodevelopmental delay characterized by intellectual disability, autistic features, and microcephaly, also known as AUTS2 syndrome. While the phenotype associated with large deletions and duplications of AUTS2 is well established, clinical features of patients harboring AUTS2 sequence variants have not been extensively described. In this study, we describe the phenotype of five new patients with AUTS2 pathogenic variants, three of them harboring loss-of-function sequence variants. The phenotype of the patients was characterized by attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) or autistic features and mild global developmental delay (GDD) or intellectual disability (ID), all in 4/5 patients (80%), a frequency higher than previously reported for ADHD and autistic features. Microcephaly and short stature were found in 60% of the patients; and feeding difficulties, generalized hypotonia, and ptosis, were each found in 40%. We also provide the aggregated frequency of the 32 items included in the AUTS2 syndrome severity score (ASSS) in patients currently reported in the literature. The main characteristics of the syndrome are GDD/ID in 98% of patients, microcephaly in 65%, feeding difficulties in 62%, ADHD or hyperactivity in 54%, and autistic traits in 52%. Finally, using the location of 31 variants from the literature together with variants from the five patients, we found significantly higher ASSS values in patients with pathogenic variants affecting the 3′ end of the gene, confirming the genotype-phenotype correlation initially described.

Purpose Prenatal diagnosis with ultrasound findings compatible with skeletal dysplasia due to FGFR3 mutations over a 9 year period in pregnancies and abortuses. Methods 54 samples were studied. Aneuploidy studies were carried out on all samples. By sequencing analysis, we determined mutations for achondroplasia (ACH), hypochondroplasia (HCH), and type I and type II tanathophoric dysplasia (TD). Results 2 chorionic villi samples had a G380R mutation due to a mother with ACH; 4 amniotic fluid samples with TDs in which the foetuses had micromelia plus hypoplastic thoraces; 5 samples from abortuses with TDs. Neither ACH nor HCH occurred in sporadic cases. Conclusions Molecular studies in ongoing pregnancies are indicated in cases with an affected parent, a family history with positive molecular studies (maternal anxiety), and when the US finding demonstrates micromelia with a hypoplastic thorax. A protocol for tissues of abortuses should include an X-ray, pathologic anatomy, and genetic studies.

Acromesomelic dysplasia, Grebe type is a very rare skeletal dysplasia characterized by severe dwarfism with marked micromelia and deformation of the upper and lower limbs, with a proximodistal gradient of severity. CDMP1 gene mutations have been associated with Grebe syndrome, Hunter-Thompson syndrome, Du Pan syndrome and brachydactyly type C. The proband is a 4-year-old boy, born of consanguineous Pakistani parents. Radiographic imaging revealed features typical of Grebe syndrome: severe shortening of the forearms with an acromesomelic pattern following a proximodistal gradient, with distal parts more severely affected than medial parts; hypoplastic hands, with the phalangeal zone more affected than the metacarpal zone; and severe hypoplastic tibial/femoral zones in both limbs. After molecular analyses, the p.Arg377Trp variant in a homozygous pattern was identified in the CDMP1 gene in the affected child. In silico and structural analyses predicted the p.Arg377Trp amino acid change to be pathogenic. Of the 34 mutations described in the CDMP1 gene, four different missense mutations have been associated with Grebe syndrome. The CDMP1 gene encodes growth differentiation factor 5 (GDF5), which plays a role in regulation of limb patterning, joint formation and distal bone growth. Homozygous mutations in the mature domain of GDF5 result in severe limb malformations such as the Grebe type or the Hunter-Thompson type of acromesomelic chondrodysplasia. The p.Arg377Trp mutation is located within the recognition motif at the processing site of GDF5 where the sequence RRKRR changes to WRKRR. The genotype-phenotype correlation allowed not only confirmation of the clinical diagnosis but also appropriate genetic counselling to be offered to this family.

Xq28 microduplications including the MECP2 gene constitute a 100% penetrant X-linked syndrome in males caused by overexpression of normal MeCP2 protein. A small number of cases of affected females have been reported. This can be due to the location of the duplicated material into an autosome, but it can also be due to the location of the duplicated material into one of the X chromosomes and random or unfavorable skewed X chromosome inactivation, which is much more likely to occur but may be underdiagnosed because of the resulting broad phenotypic spectrum. In order to contribute to the phenotypic delineation of Xq28 microduplications including MECP2 in symptomatic females, the authors present clinical and molecular data on 3 patients illustrating the broad phenotypic spectrum. Our finding underlines the importance of quantitative analysis of MECP2 in females with intellectual disability and raises the question of the indication in females with borderline intellectual performances or learning difficulties.