A patient is being investigated for chronic diarrhoea. Small intestinal mucosal biopsy shows PAS positive foamy macrophages. The diagnosis is probably -

Whipple's disease is a rare condition characterised by infiltration of small imtestinal mucosa by foamy macrophages, which stain positive with periodic acid-schiff reagent. It is caused by infection with Gram positive bacillusTropheryma whipplei, which becomes resident in the bowel mucosa. Clinical features include diarrhea ,steatorrhea,weight loss,ascites, sacroiliitis,protein losing enteropathy, apathy,fits,pleurisy. Reference Harrison20th edition pg 1103