A female patient with a three year history of Crohn's disease of the c
olon developed myasthenia gravis. Despite diversion of the faecal stre
am by an ileostomy, and total colectomy, the patient had continuing pr
oblems with perineal and perianal abscesses and fistulas. Her myasthen
ia gravis became unresponsive to anti-cholinergics so a thymectomy was
performed. The perineal and perianal disease improved subsequently. T
his case supports the theory that functional disturbances of the thymu
s may have a role in the pathogenesis of inflammatory bowel disease.