Deletion of the long arm of chromosome 6: two new patients and literature review

Subtelomeric deletions of chromosome 6q may result in a syndrome with brain malformations, comprising hydrocephalus and hypoplasia of the corpus callosum. Aplasia of the olfactory bulbs (OB) or anosmia has not been described in this syndrome. We describe a 3-year-old girl and a 25-year-old man with subtelomere 6q deletions. Both patients had aplastic OB and hydrocephalus. Subtelomeric 6q deletions might be underdiagnosed as anosmia can be the only symptom.

Section: Discussionmentioning

confidence: 79%

Expanding the clinical and neuroradiological phenotype of 6q27 microdeletion: Olfactory bulb aplasia and anosmia

Gerber¹,

Neuhann²,

Tyshchenko³

et al. 2011

“…It seems that the deletion of 7q and the SHH and HLXB9 genes did not have any significant effects on phenotype in patients 2 and 3, even though the deletion in these patients was larger than in patient 1. Other symptoms such as growth and intellectual disability, hypotonia, hypotelorism, and urogenital anomalies are common to most chromosomal deletions [Telford et al, ; Evers et al, ; Scigliano et al, ; Hiraki et al, ]. In summary, there are many genes present on different chromosomes that play a significant role in the normal development of the human brain.…”

Section: Discussionmentioning

confidence: 99%

Three new cases of terminal deletion of the long arm of chromosome 7 and literature review to correlate genotype and phenotype manifestations

Ayub

Gadji

Krabchi

et al. 2016

Partial monosomy of the long arm of chromosome 7 has been characterized by wide phenotypic manifestations, but holoprosencephaly (HPE) and sacral agenesis have frequently been associated with this chromosomal deletion. A clear relationship between genotype and phenotype remains to be defined in the 7q deletion syndrome. Three patients (1, 2, and 3) were investigated with 7q terminal deletion and compared with similar deletion cases in the literature in order to stratify the phenotypes associated with 7q35 and 7q36 terminal deletion patients. Patients 1, 2, and 3 were carrying a de novo terminal deletion at bands 7q36.2, 7q35, and 7q36.1, respectively. In patient 3, a small Xq28 duplication was also identified by array-CGH. Our patients presented with heterogeneous phenotypic manifestations, which could imply the possible role of environmental factors (multifactorial inheritance), structural variations in the non-coding regions, penetrance, and/or polymorphism. The varying length of deletion was also taken into account. Growth retardation was the most frequent symptom found in both 7q35 and 7q36 patients we reviewed. The occurrence of HPE and sacral malformation together was seen in less than 10% of the reviewed cases in both kinds of deletion. HPE was associated mainly in cases with an unbalanced translocation.

“…Genotype-phenotype correlations have emerged for specific breakpoints dividing deletions of the long arm of chromosome 6 into four groups [Evers et al, 1996;Hopkin et al, 1997;Sukumar et al, 1999;Eash et al, 2005;Bertini et al, 2006;Elia et al, 2006]. One of the limitations of these studies is a lack of molecular data to determine the exact size of the deletions.…”

Section: Discussionmentioning

confidence: 99%

Paternal deletion 6q24.3: A new congenital anomaly syndrome associated with intrauterine growth failure, early developmental delay and characteristic facial appearance

Nowaczyk

Carter

et al. 2008

Deletions of the long arm of chromosome 6 are relatively uncommon and to date minimal genotype-phenotype correlations have been observed. We report on three unrelated patients with de novo paternal interstitial deletions of 6q24.3. FISH mapping was used to delineate the minimal region of overlap between these three patients. Although all three patients had different size deletions and different breakpoints, two of the patients shared a 2.5 Mb region of overlap and strikingly similar facial features including a triangular face, frontal bossing with metopic prominence, short and upward-slanting palpebral fissures, asymmetry of upper eyelids, hooded eyelids, shallow orbits, prominent inferior orbital crease, wide mouth, and long and flat philtrum. They also had redundant skin, joint laxity, a small thorax, and early developmental delay. The smallest region of overlap between all three patients was a region of deletion less than 1 Mb; all had a history of IUGR and postnatal short stature without overt radiologic skeletal anomalies. The dysmorphic features, early developmental and growth delay may be due to the hemizygous state for one of the genes in the deleted region of two of the patients or to a long range effect of the deletion on expression of other genes. In addition, since imprinted genes have been reported in this region, paternal deletion of an imprinted gene in all three patients may contribute to the growth phenotype. We propose that this is a new congenital malformation syndrome associated with a paternal deletion of 6q24.3.