We have been unable to detect any abnormality in the structure or function of the small bowel in eight psoriatic patients who underwent studies of fecal fat excretion, xylose excretion, microscopic (routine, dissection, and electron) examination of jejunal mucosa, and roentgenographic examination.
Preger L, Maibach HI, Osborne RB, Shapiro HA, Lee JC. On the Question of Psoriatic Enteropathy. Arch Dermatol. 1970;102(2):151-153. doi:10.1001/archderm.1970.04000080023004