Interstitial deletion of chromosome 7q in a patient with Williams syndrome and infantile spasms

Interstitial deletion of 7q11.23–q21.11 was identified by cytogenetic methods in a 4-year-old boy with Williams syndrome (WS) and infantile spasms. Deletion of the elastin (ELN) gene and the DNA polymorphic markers, D7S1870, D7S2490, D7S2518, and D7S2421, were identified in the patient, but the loci for D7S653 and D7S675 were not involved. Zackowski et al. (1990) reported that 6 of 16 patients with the interstitial deletion of 7q11.2–q22 had abnormal electro encephalograms, or seizures, or both, and that infantile spasms were present in 2 of the 6 patients. WS is a well defined developmental disorder characterized by distinct facial features, gregarious personality, and congenital heart defects. Seizures are not generally associated with this syndrome. WS commonly is characterized by deletion of the loci for ELN and D7S1870, but not those for D7S2490, D7S2518, or D7S2421. This suggests that a gene responsible for infantile spasms is located in the 2.7-cM interval between loci D7S1870 and D7S675. Received: April 27, 1998 / Accepted: May 29, 1998     

Vaccine‐associated varicella and rubella infections in severe combined immunodeficiency with isolated CD4 lymphocytopenia and mutations in IL7R detected by tandem whole exome sequencing and chromosomal microarray

In areas without newborn screening for severe combined immunodeficiency (SCID), disease‐defining infections may lead to diagnosis, and in some cases, may not be identified prior to the first year of life. We describe a female infant who presented with disseminated vaccine‐acquired varicella (VZV) and vaccine‐acquired rubella infections at 13 months of age. Immunological evaluations demonstrated neutropenia, isolated CD4 lymphocytopenia, the presence of CD8⁺ T cells, poor lymphocyte proliferation, hypergammaglobulinaemia and poor specific antibody production to VZV infection and routine immunizations. A combination of whole exome sequencing and custom‐designed chromosomal microarray with exon coverage of primary immunodeficiency genes detected compound heterozygous mutations (one single nucleotide variant and one intragenic copy number variant involving one exon) within the IL7R gene. Mosaicism for wild‐type allele (20–30%) was detected in pretransplant blood and buccal DNA and maternal engraftment (5–10%) demonstrated in pretransplant blood DNA. This may be responsible for the patient's unusual immunological phenotype compared to classical interleukin (IL)‐7Rα deficiency. Disseminated VZV was controlled with anti‐viral and immune‐based therapy, and umbilical cord blood stem cell transplantation was successful. Retrospectively performed T cell receptor excision circle (TREC) analyses completed on neonatal Guthrie cards identified absent TREC. This case emphasizes the danger of live viral vaccination in severe combined immunodeficiency (SCID) patients and the importance of newborn screening to identify patients prior to high‐risk exposures. It also illustrates the value of aggressive pathogen identification and treatment, the influence newborn screening can have on morbidity and mortality and the significant impact of newer genomic diagnostic tools in identifying the underlying genetic aetiology for SCID patients.     

Missense mutation in the ATPase,aminophospholipid transporter protein ATP8A2 is associated with cerebellar atrophy and quadrupedal locomotion

Cerebellar ataxia, mental retardation and dysequilibrium syndrome is a rare and heterogeneous condition. We investigated a consanguineous family from Turkey with four affected individuals exhibiting the condition. Homozygosity mapping revealed that several shared homozygous regions, including chromosome 13q12. Targeted next-generation sequencing of an affected individual followed by segregation analysis, population screening and prediction approaches revealed a novel missense variant, p.I376M, in ATP8A2. The mutation lies in a highly conserved C-terminal transmembrane region of E1 E2 ATPase domain. The ATP8A2 gene is mainly expressed in brain and development, in particular cerebellum. Interestingly, an unrelated individual has been identified, in whom mental retardation and severe hypotonia is associated with a de novo t(10;13) balanced translocation resulting with the disruption of ATP8A2. These findings suggest that ATP8A2 is involved in the development of the cerebro-cerebellar structures required for posture and gait in humans.     

Compound heterozygous mutations in TTC7A cause familial multiple intestinal atresias and severe combined immunodeficiency

Familial multiple intestinal atresias is an autosomal recessive disease with or without combined immunodeficiency. In the last year, several reports have described mutations in the gene TTC7A as causal to the disease in different populations. However, exact correlation between different genotypes and various phenotypes are not clear. In this study, we report identification of novel compound heterozygous mutations in TTC7A gene in a Malay girl with familial multiple intestinal atresias and severe combined immunodeficiency (MIA‐SCID) by whole exome sequencing. We found two mutations in TTC7A: one that destroyed a putative splicing acceptor at the junction of intron 17/exon 18 and one that introduced a stop codon that would truncate the last two amino acids of the encoded protein. Reviewing the recent reports on TTC7A mutations reveals correlation between the position and nature of the mutations with patient survival and clinical manifestations. Examination of public databases also suggests carrier status for healthy individuals, making a case for population screening on this gene, especially in populations with suspected frequent founder mutations.