CSGALNACT1‐congenital disorder of glycosylation: A mild skeletal dysplasia with advanced bone age

Congenital disorders of glycosylation (CDGs) comprise a large number of inherited metabolic defects that affect the biosynthesis and attachment of glycans. CDGs manifest as a broad spectrum of disease, most often including neurodevelopmental and skeletal abnormalities and skin laxity. Two patients with biallelic CSGALNACT1 variants and a mild skeletal dysplasia have been described previously. We investigated two unrelated patients presenting with short stature with advanced bone age, facial dysmorphism, and mild language delay, in whom trio‐exome sequencing identified novel biallelic CSGALNACT1 variants: compound heterozygosity for c.1294G>T (p.Asp432Tyr) and the deletion of exon 4 that includes the start codon in one patient, and homozygosity for c.791A>G (p.Asn264Ser) in the other patient. CSGALNACT1 encodes CSGalNAcT‐1, a key enzyme in the biosynthesis of sulfated glycosaminoglycans chondroitin and dermatan sulfate. Biochemical studies demonstrated significantly reduced CSGalNAcT‐1 activity of the novel missense variants, as reported previously for the p.Pro384Arg variant. Altered levels of chondroitin, dermatan, and heparan sulfate moieties were observed in patients’ fibroblasts compared to controls. Our data indicate that biallelic loss‐of‐function mutations in CSGALNACT1 disturb glycosaminoglycan synthesis and cause a mild skeletal dysplasia with advanced bone age, CSGALNACT1‐CDG.     

Further delineation of putative ACTB loss‐of‐function variants: A 4‐patient series

ACTB encodes β‐cytoplasmic actin, an essential component of the cytoskeleton. Based on chromosome 7p22.1 deletions that include the ACTB locus and on rare truncating ACTB variants, a phenotype resulting from ACTB haploinsufficiency was recently proposed. We report putative ACTB loss‐of‐function variants in four patients. To the best of our knowledge, we report the first 7p22.1 microdeletion confined to ACTB and the second ACTB frameshifting mutation that predicts mRNA decay. A de‐novo ACTB p.(Gly302Ala) mutation affects β‐cytoplasmic actin distribution. All four patients share a facial gestalt that is distinct from that of individuals with dominant‐negative ACTB variants in Baraitser‐Winter cerebrofrontofacial syndrome. Two of our patients had strikingly thin and sparse scalp hair. One patient had sagittal craniosynostosis and hypospadias. All three affected male children have attention deficits and mild global developmental delay. Mild intellectual disability was present in only one patient. Heterozygous ACTB deletion can allow for normal psychomotor function.     

Ewing's sarcoma. New clinico-pathological aspects

Ewing's sarcoma is a rare, but highly malignant bone tumor. During the years 1966-1983 we diagnosed and treated this tumor in 84 patients. Diagnosis of the tumor in an early stage is a prerequisite for successful therapy. Clinical and radiological findings contribute to the diagnosis, but histologic confirmation is indispensible. In addition to histomorphology we regard electron microscopy and the demonstration of glycogen as essential for the final diagnosis. The differential diagnosis includes haematogeneous osteomyelitis, malignant lymphoma, metastases from neuroblastomas, rhabdomyosarcoma and some benign bone tumors. New observations concerning the histogenesis of Ewing's sarcoma are discussed. The introduction of chemotherapy as part of a multimodality approach to treatment has substantially improved the prognosis in comparison to the previous results with surgery and radiation therapy. The role of surgery and radiation independently and in combination is discussed. We propose an approach to treatment based on our experience which involves surgical removal of the primary tumor after preoperative chemotherapy. The overall survival rate among our 84 patients was 40%. Among those who were diagnosed early and treated according to the recommended protocol 54% are alive.