This is a rare bacterial infection
attributed to Tropheryma whippelii which affects the small bowel in a diffuse fashion
but can also involve many
other systems.There may be an underlying immunologic defect in these patients, possibly genetically
determined, but this
has not been clearly established.
Typical patients are middle-aged women,
who present with fever,
malabsorption and weight loss, arthritis, and Iymphadenopathy. Central nervous
system manifestations, including ophthalmoplegia and personality change,
have been reported in about 10% of patients.
The mucosal folds appear thickened
and are patchily coated with yellow-white material.
On closer inspection, these patches
or plaques may represent enlarged bulbous villi. Previously, it was believed
that the proximal small bowel was
always affected in a diffuse fashion. However,some patients may have only
spotty involvement of the
lamina propria, and some biopsy specimen may not contain any characteristic macrophages. Direct viewing
endoscopy offers an advantage because the focal yellow areas can be selectively
Histologically, the only other disorder
that may cause a problem in differential diagnosis is Mycobacterium avium-intracellulare
in patients with AIDS. Acid-fast stains should therefore be done when
macrophages are present in the lamina propria. Massive infection with
M. avium has been termed pseudo- Whipple's disease, but the macrophages
look completely different, even at the light microscopic level.
In AIDS in the absence of M. avium,
small clumps of unexplained PAS-positive macrophages are occasionally
observed in the small bowel mucosa, but they are very patchily distributed
and the intensity of their PAS positivity is variable.
Histoplasmosis may be associated with
a macrophage infiltrate, but if that is part of the differential diagnosis
clinically, then fungal stains should be done.
Involvement of the colon is extremely
rare in Whipple's disease.
(Ref. Ackerman's Surgical Pathology,