Pennings investigated Wolfram syndrome and Usher syndrome. These are two inherited syndromes that cause both deafness and blindness. Female patients with Wolfram syndrome were found to have significantly worse hearing than male patients.
Usher syndrome causes about fifty percent of deaf-blindness cases. This syndrome is characterised by hearing impairment and a retinal disorder. Patients develop tunnel vision and can even become blind.
Various forms of Usher syndrome exist. USH2a and USH1b are the most prevalent variants in the Netherlands. Pennings discovered that the hearing of USH2a patients gradually deteriorates. Each year these patients hear about half a decibel less. Up until now clinicians thought that USH2a patients had a stable hearing loss, which only worsened due to ageing. However, the increase in the hearing loss now appears to be greater.
The researcher also discovered that the onset of the deterioration in vision probably occurs later in USH2a patients than USH1b patients. Eventually, between the ages of 40 and 50 years, the vision of the patients will be the same for both variants, due to a greater decrease in the vision of USH2a patients, and in subsequent years an increasing number of patients will become blind.
Wolfram syndrome is a rare condition of the nervous tissue. Patients with the syndrome suffer, for example, from diabetes and a deterioration of the optic nerve that results in blindness at a young age. Disorders of the urine-concentrating mechanism and a progressive loss of hearing also occur.
Physicians can use the results from this study to provide patients and their families with more detailed and accurate information about the condition. It will also enable physicians to establish a more accurate diagnosis and on the basis of this to offer patients the possibility of DNA diagnostics.
The research was funded by Netherlands Organisation for Health Research and Development (ZonMW).