CLUSTER OF INFLAMMATORY BOWEL DISEASE IN THREE CLOSE COLLEGE FRIENDS?
Aisenberg J; Janowitz HD  Division of Gastroenterology, Mount Sinai School of Medicine of the City University of New York, New York 10029. J Clin Gastroenterol, 1993 Jul, 17:1, 18-20

Although the etiology of inflammatory bowel disease remains unknown, current evidence favors the interplay of genetic predisposition with environmental factors. Clustering of inflammatory bowel disease in spouses had been described, and supports a role for an environmental agent. We describe three unrelated, unmarried men all attorneys who enjoyed a close, sustained friendship in college, and who within a decade of their contact developed inflammatory bowel disease. We describe the nature of their college contact, the course of their inflammatory bowel disease, and relate our cluster to the scanty literature on clustering in inflammatory bowel disease. Physicians should report similar observations to illuminate the roles of genetics and environment in the development of these illnesses.
 

CAUSATION OF CROHN'S DISEASE: THE IMPACT OF CLUSTERS.
Hermon-Taylor J. Gastroenterology 1993 Feb;104(2):643-6

Van Kruiningen et al. describe the clustering of Crohn's disease in two families in northern France. In the first family, the father, mother, and all children, three sons and one daughter, developed Crohn's disease. One of the sons who developed Crohn's disease in 1974 met a girl 3 years later whom he subsequently married in 1983. She developed Crohn's disease in 1991. In the second family, neither the mother nor the father had Crohn's disease; however, four of the five sons and three of the six daughters developed Crohn's disease. These events represent the most concentrated clustering of Crohn's disease ever reported.

Throughout this in-depth study, there were two positive findings of potential significance. The first was elevated titers of antibody to Breda virus in 6 of 10 patients and in 2 of 5 unaffected family members. The second was that of the total of 13 cases of Crohn's disease between the two families, there seemed to be a distinct periodicity in disease emergence; 7 cases from 1970 to 1974 (4 in one family within 10 months from 1972 to 1973) and 4 cases from 1982 to 1984. The authors conclude that the outbreak of Crohn's disease in theses families suggests a causative infectious micro-organism with a considerable latency interval between exposure and the emergence of clinical disease.
 

CLUSTERING OF CROHN’S DISEASE IN A COTSWOLD VILLAGE.
Allan RN; Pease P; Ibbotson JP; Q J Med, 1986 May, 59:229, 473-8
 
The first large cluster of patients with Crohn’s disease, identified in the parish of Blockley,
Gloucestershire is reported. Twelve patients with Crohn’s disease have been identified of whom only two (a father and daughter) are known to be related. The age and sex distribution and macroscopic site of disease at diagnosis is similar to that expected in an unselected series. The identification of such a cluster suggests that environmental factors may be important in pathogenesis.

The observed number of patients( 12 ) was much higher than expected number( 1.8 ) for
parish population of ca. 2000. Inquiries in adjacent parishes have not revealed any excess of patients. Only 2 patients with ulcerative colitis were identified in the parish. The size of the cluster is such that it is unlikely to have occurred by chance. Since the area is relatively isolated, inter-marrying in the past was a potential genetic factor, but HLA and complement typing of the patients and their families has excluded this possibility. The parish has its own water supply, again extensive microbiological sampling have not identified a possible waterborne infectious agent. Geochemical survey did not suggest any trace metal deficiency of the soil, particularly in zinc and copper that might alter intestinal permeability and predispone individuals in the area to Crohn's.
 

CROHN’S DISEASE—IS THERE A LONG LATENT PERIOD?
Reilly RP; Robinson TJ; Postgrad Med J, 1986 May, 62:727, 353-4

Four cases of Crohn’s disease developing in adult females, who had been in close contact during
their teens, are described. It is suggested that this could indicate an infective causation for Crohn’s disease with a long latency.
 

OBSERVATIONS ON 261 CONSECUTIVE PATIENTS WITH INFLAMMATORY BOWEL DISEASE SEEN IN THE SOUTHWEST UNITED STATES.
Robinson WW, Bentlif PS, Kelsey JR Jr. Dig Dis Sci 1980;25:198-204.

It is interesting to note that 13 IBD patients live in the community of Orange (population 25,000), in the far southeast corner of Texas. Of these 13 patients, 8 had Crohn's disease. Four of our eight patients were natives of Orange, while the other four patients moved to Orange prior to the onset of their disease.The incidental observation of a large number of cases of IBD occurring in Orange, Texas, is of special interest and suggests that to some extend there is clustering of cases in this area of population (very apparent from the map in Fig 4).