Complex Mosaic Ring Chromosome 11 Associated with Hemizygous Loss of 8.6 Mb of 11q24.2qter in Atypical Jacobsen Syndrome

Abstract

Jacobsen syndrome (JBS) is a contiguous gene deletion syndrome involving terminal chromosome 11q. The haploinsufficiency of multiple genes contributes to the overall clinical phenotype, which can include the variant Paris-Trousseau syndrome, a transient thrombocytopenia related to FLI1 hemizygous deletion. We investigated a boy with features of JBS using classic cytogenetic methods, FISH and high-resolution array CGH. The proband was found to have a mosaic ring chromosome 11 resulting in a hemizygous 11q terminal deletion of 8.6 Mb, leading to a copy number loss of 52 genes. The patient had a hemizygous deletion in the FLI1 gene region without apparent thrombocytopenia, and he developed diabetes mellitus type I, which has not previously been described in the spectrum of disorders associated with JBS. The relationship of some of the genes within the context of the phenotype caused by a partial deletion of 11q has provided insights concerning the developmental anomalies presented in this patient with atypical features of JBS.

Ten-year use of recombinant parathyroid hormone for the treatment of hypoparathyroidism in a boy with partial Jacobsen syndrome

“…However, no cardiac malformations were detected despite the presence of the JAM3 gene mutation, usually considered a candidate gene for the cardiac phenotype [ 2 , 6 ]. Interestingly, JAM3 gene deletion, one of the 4 genes ( FLI1, ETS1, NFRKB , and JAM3 ) related to thrombocytopenia did not manifest with Paris-Trousseau syndrome in our patient, similar to some previous cases [ 6 , 7 ]. The partial expression of the JS phenotype in our patient may be related to the size of terminal deletion, as the most severe phenotype is usually seen in patients with the largest deletions [ 2 ].…”