In one and the same person, diseases may occur randomly combined with the frequency of the probability product of the considered diseases, but it is also possible that they occur in combination for various reasons, either over- or under-probably. How often is the combination of type 1 diabetes and Parkinson's disease observed in the elderly? Are there special treatment options for Parkinson's disease for those people? Is it possible that diabetologists understand too little about Parkinson's disease and neurologists too little about type 1 diabetes? These questions were asked by a 76-year-old man who has had well-adjusted type 1 diabetes for about 60 years and has been suffering from increasing Parkinson's symptoms for about 6 years. In my very large patient base of type 1 diabetics (> 5000, including an increasing number of type 1 diabetics over the age of 60), whom I have been able to look after for up to 40 years, he is the only one I remember. Although I know of a few with cortex atrophies and brainstem insults, even these did not develop clinically tangible symptoms of Parkinson's disease. However, since Parkinson's disease is the 2nd most common neurodegenerative disease worldwide, I am surprised. Who can contribute to this from own experience?