Clinical Information

Whipple disease is a chronic, systemic illness that, in the majority of cases, involves the small intestine and its lymphatic drainage. The disease primarily affects adults of middle age, with a peak incidence in the third and fourth decades of life. Clinical findings may include malabsorption, chronic diarrhea, abdominal pain, arthralgia, fever, and central nervous system symptoms.

Pathologic changes associated with Whipple disease are distinctive, with diagnosis dependent on histologic examination of biopsy specimens from involved tissues. Electron microscopic or special high-resolution light microscopic examination of the lamina propria of the small intestine of patients with untreated Whipple disease reveals many rod-shaped bacillary organisms. These tiny bacilli, referred to as Whipple bacilli, measure about 0.25 micrometer long and are seen as periodic acid-Schiff-positive granules within macrophages. These inclusions represent fragments of the cell walls from degenerating bacilli.

Culture of Whipple bacilli from biopsy material is laborious, and the organism is very slow growing. Definitive identification of the Whipple-associated bacillus has been difficult because of these limitations. Molecular techniques using polymerase chain reaction and nucleotide sequencing allow classification of this bacillus as an actinomycete not closely related to any other known species, which has been named Tropheryma whipplei.