Photosensitivity in a patient with C9orf72 repeat expansion

Abstract

The phenotype of C9ORF72 repeat expansions is rapidly expanding. Originally found to be the major genetic cause of familial frontotemporal dementia with amyotrophic lateral sclerosis, several other clinical characteristics have been described more recently. Here, we report on a family diagnosed with ‘degenerative schizophrenia’ and harbouring a C9ORF72 repeat expansion, in which at least the index patient and an uncle showed a photoparoxysmal response during electroencephalography. Whereas epilepsy has been described in several repeat expansion disorders, photosensitivity has thus far only been reported in dentatorubral-pallidoluysian atrophy. The photoparoxysmal response may therefore be a new clinical feature of C9ORF72 repeat expansion related disease. Our observation learns that a repeat expansion disorder like C9ORF72 should be considered in patients with a combination of young-onset dementia, psychiatric symptoms and/or photosensitive epilepsy. We advocate the occasional use of EEG in the dementia workup and in particular urge to consider provocative tests such as photic stimulation.

Key words:

• Frontotemporal dementia
• repeat expansion disorders
• electroencephalography
• EEG
• photoparoxysmal response

Acknowledgements

The authors would like to thank Danitsja Hoff-van Leeuwen for composing the pedigree shown in Figure 2.

Figure 2. Pedigree of the family:

• Members 8, 10, 14 and 15: admitted to same mental health care institution with schizophrenia and young-onset dementia; brain autopsy inconclusive for patients 10 and 14.

• Members 18 and 20: diagnosed with frontotemporal dementia.

• Members 19 and 21 (index patient): known C9orf72 repeat expansion

• Patient 17: lineage uncertain, phenotype identical to index patient, electroencephalography describing intermittent slowing and a photoparoxysmal response (PPR). Reported to be a cousin of family members 8, 10, 14 and 15.

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