The so-called Helsingborg Disease is an intestinal degenerative neuropathy discovered in a kindred in South Sweden. Affected subjects develop severe intestinal symptoms, the most common being chronic diarrhea, but abdominal pain, constipation and severe vomiting are common. Chronic intestinal pseudo-obstruction is the end-stage with high mortality from intestinal failure. Two families with affected members were shown by histopathology and genealogy to be one large kindred with the same underlying disease. Genetic analysis shows that this disease, having an autosomal dominant transmission, is strongly linked to a region in the short arm of chromosome 9 and a 1.2 Mb duplication in this region. The duplication includes 22 protein-coding genes, most of them are interferon genes. Family members not carrying the duplication have no increased prevalence of gut diseases. Genetic analysis including gene-dose array should be important for etiologic diagnosis and for genetic guidance in this kindred.