Case report
Pathogenesis of vestibular schwannoma in ring chromosome 22
1 Department of human genetics, University Hospital Gasthuisberg, Leuven, Belgium
2 Department of Paediatrics, University Hospital Gasthuisberg, Leuven, Belgium
3 Genetic Medicine, Manchester Academic Health Science Centre, St Mary's hospital, Manchester, UK
4 Department of Neurosurgery, University Hospital Gasthuisberg, Leuven, Belgium
5 Department of Pathology, University Hospital Gasthuisberg, Leuven, Belgium
BMC Medical Genetics 2009, 10:97 doi:10.1186/1471-2350-10-97
Published: 22 September 2009Abstract
Background
Ring chromosome 22 is a rare human constitutional cytogenetic abnormality. Clinical features of neurofibromatosis type 1 and 2 as well as different tumour types have been reported in patients with ring chromosome 22. The pathogenesis of these tumours is not always clear yet.
Methods
We report on a female patient with a ring chromosome 22 presenting with severe mental retardation, autistic behaviour, café-au-lait macules and facial dysmorphism. Peripheral blood lymphocytes were karyotyped and array CGH was performed on extracted DNA. At the age of 20 years she was diagnosed with a unilateral vestibular schwannoma. Tumour cells were analyzed by karyotyping, array CGH and NF2 mutation analysis.
Results
Karyotype on peripheral blood lymphocytes revealed a ring chromosome 22 in all analyzed cells. A 1 Mb array CGH experiment on peripheral blood DNA showed a deletion of 5 terminal clones on the long arm of chromosome 22. Genetic analysis of vestibular schwannoma tissue revealed loss of the ring chromosome 22 and a somatic second hit in the NF2 gene on the remaining chromosome 22.
Conclusion
We conclude that tumours can arise by the combination of loss of the ring chromosome and a pathogenic NF2 mutation on the remaining chromosome 22 in patients with ring chromosome 22. Our findings indicate that patients with a ring 22 should be monitored for NF2-related tumours starting in adolescence.
