Joshua Ferris's The Unnamed (2010) has as its central character Tim Farnsworth, a lawyer afflicted with compulsive walking. At several points in the novel is is noted that he is the only person who has ever had this disorder: 'I'm the only one ... No one else on record. That's crazy.'
It is crazy because a characters who has been to Switzerland for clinical treatment might have been thought to have come across Ian Hacking's book Mad Travellers (2002) which is about cases of compulsive walking in late nineteenth century France... particularly Albert Dadas, who is mentioned in the wikipedia entry on dromomania. A disorder also familiar to readers of Virilio's Speed and Politics (1977).
In case we might think this is unreliable narrator, the more reliable daughter Becky notes: 'but who had ever heard of what he had? Not even the Internet.' (94)
1. So we can conclude that despite being in ever other way similar to our world (excepting, perhaps, the extreme weather conditions) the world of the novel lacks 'dromomania'
2. Or, Ferris never encountered Hacking's book or the diagnosis, despite all the consulting of authorities listed in the acknowledgements
3. Or, he expects his readers not to know about it.