Whipple's disease is a rare, chronic, multisystemic infectious disease caused by Tropheryma whipplei bacteria. It most commonly involves the gastrointestinal system (jejunum predominant), mesenteric and retroperitoneal lymph nodes, joints, and central nervous system. Most frequent in middle-aged white males with a prevalence below 1 per million. The clinical triad consists of diarrhea, weight loss, and arthralgia, usually developing after years of prodromal arthralgia. On CT, jejunal wall thickening and markedly low-density mesenteric/retroperitoneal lymph nodes (fat deposition — -10 to +20 HU range) are pathognomonic. This low density reflects accumulation of lipid-laden macrophages within lymph nodes and is distinguishing from all other causes of lymphadenopathy. On MRI, T1 hyperintense signal in lymph nodes with signal loss on fat suppression confirms fat content. Diagnosis is established by duodenal biopsy (PAS-positive macrophages — foamy histiocytes accumulating in lamina propria) and T. whipplei PCR. Fatal without treatment, but cure is possible with appropriate antibiotic therapy (initial IV ceftriaxone followed by prolonged trimethoprim-sulfamethoxazole).
Age Range
30-70
Peak Age
50
Gender
Male predominant
Prevalence
Rare
Tropheryma whipplei is a gram-positive bacillus widely found in the environment but rarely causing disease — disease development depends on specific host immune defect (particularly T cell dysfunction and macrophage activation failure). Bacteria are phagocytosed by intestinal mucosal macrophages but intracellular killing mechanism is insufficient — bacteria multiplying within macrophages accumulate as PAS-positive (periodic acid-Schiff) granular material. These lipid and bacteria-laden macrophages infiltrate villus lamina propria, causing villus expansion and malabsorption. Lymphatic obstruction (from macrophage infiltration) disrupts intestinal lymphatic drainage and lipid absorption is impaired — lipid-laden macrophages accumulate in mesenteric and retroperitoneal lymph nodes. Low density in lymph nodes on CT (-10 to +20 HU range) results from low X-ray attenuation of lipid-laden macrophages (chylous material + fat droplets). Jejunal wall thickening results from villus expansion and macrophage infiltration of lamina propria. T1 hyperintense lymph nodes on MRI derive from short T1 relaxation time of lipid content — signal loss on fat-suppressed sequences confirms fat presence. Extra-intestinal involvement (arthritis, cardiac, neurological) reflects hematogenous and lymphatic bacterial spread.
Low density approaching fat density (-10 to +20 HU) in mesenteric and retroperitoneal lymph nodes — pathognomonic CT finding for Whipple's disease. Reflects intranodal accumulation of lipid-laden macrophages and clearly distinguishes from all other LAP causes (lymphoma: 30-50 HU, TB: rim pattern 10-30 HU center, metastasis: 30-60 HU). This single finding, in appropriate clinical context, should strongly suggest Whipple's diagnosis.
Markedly low density is observed in mesenteric and retroperitoneal lymph nodes (-10 to +20 HU). This low density is significantly lower than normal lymph node density (30-50 HU) and reflects lipid/fat deposition. Lymph nodes may be enlarged (>1 cm short axis) but density characteristic is far more important than size. Enhancement is minimal because lipid-laden macrophages are a non-vascular component. This finding is virtually pathognomonic for Whipple's disease and allows differentiation from all other LAP causes (lymphoma, metastasis, TB, sarcoidosis).
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Markedly low density (mean [value] HU) in mesenteric and retroperitoneal lymph nodes consistent with intranodal fat deposition — suggesting Whipple's disease.
Segmental or diffuse wall thickening and mucosal fold prominence in the jejunum is observed. Wall thickness may reach 4-8 mm. Duodenum and ileum may also be involved but jejunal involvement predominates. Wall enhancement may be normal or mildly increased — prominent hypervascular enhancement is not expected. Thickening of mucosal folds reflects villus expansion and macrophage infiltration of lamina propria. CT enterography with neutral oral contrast provides luminal distension for accurate wall thickness assessment.
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Diffuse wall thickening and mucosal fold prominence in the jejunum, together with low-density LAP, consistent with Whipple's disease.
On MRI T1-weighted images, mesenteric lymph nodes show hyperintense signal due to lipid content. Signal loss on fat-suppressed sequences (fat-sat or STIR) — definitively confirms intranodal fat presence. This finding is the MRI correlate of low density on CT and strongly supports Whipple's diagnosis. Chemical shift imaging (in-phase/opposed-phase) can also be used for intranodal lipid demonstration — signal drop on opposed-phase confirms intravoxel fat-water mixture.
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Hyperintense signal in mesenteric lymph nodes on MRI T1, with signal loss on fat suppression confirming intranodal lipid deposition; this finding is consistent with Whipple's disease.
On non-contrast CT, increased mesenteric fat density (haziness/misty mesentery) and mesenteric edema may be observed. Chylous ascites may accompany due to lymphatic obstruction — ascites density is low (-10 to +10 HU) because triglyceride-rich content shows attenuation approaching fat. This finding reflects disruption of mesenteric lymphatic drainage due to macrophage infiltration. Mesenteric haziness results from the normal mesenteric fat density increasing due to edema and inflammatory infiltration.
Report Sentence
Increased mesenteric fat density (misty mesentery) and low-density ascites are observed, consistent with lymphatic obstruction.
On MRI T2-weighted images, jejunal wall thickening and hyperintense mucosal signal — reflecting villus expansion, lamina propria edema, and macrophage infiltration. Mucosal folds are prominent. Mild diffusion restriction on DWI may reflect chronic inflammatory infiltration but is not as prominent as in TB or lymphoma. MR enterography is valuable as a radiation-free alternative for jejunal wall thickening assessment.
Report Sentence
Hyperintense mucosal signal and wall thickening in the jejunal wall on MRI T2, consistent with malabsorptive disease.
As additional finding in Whipple's disease, sacroiliitis or peripheral joint arthropathy findings may be observed on CT. Irregularity of sacroiliac joint space, subchondral erosion, and sclerosis may be seen. Joint involvement usually begins years before GI symptoms and may be the initial presentation — therefore Whipple's should be considered in unexplained seronegative arthropathy + malabsorption combination. Synovial thickening and effusion in peripheral joints may also be seen.
Report Sentence
Inflammatory changes in sacroiliac joints, potentially consistent with extra-intestinal involvement of Whipple's disease.
Criteria
Jejunal involvement predominant. Diarrhea, steatorrhea, malabsorption, weight loss dominate the clinical picture. Most common form, comprising 80-90% of cases.
Distinct Features
Jejunal wall thickening + low-density LAP on CT is the pathognomonic combination. PAS-positive macrophages on duodenal biopsy confirm diagnosis. Anemia, hypoalbuminemia, and vitamin deficiencies from malabsorption accompany.
Criteria
GI symptoms minimal or absent. CNS involvement (dementia, supranuclear ophthalmoplegia, myoclonus, hypothalamic dysfunction) or culture-negative endocarditis may be the dominant presentation.
Distinct Features
White matter lesions, hypothalamic involvement on brain MRI. Culture-negative vegetations on echocardiography. LAP and jejunal involvement findings may be absent — diagnosis becomes challenging. T. whipplei PCR may be positive in cerebrospinal fluid.
Criteria
Polyarticular arthralgia/arthritis beginning on average 6-8 years before GI symptoms. Seronegative spondyloarthropathy-like pattern. RF and anti-CCP negative.
Distinct Features
Early diagnosis difficult — Whipple's not considered before GI symptoms appear. LAP finding may not yet be present on CT. Unexplained seronegative arthritis + later developing malabsorption should raise suspicion for Whipple's. PAS-positive macrophages may be seen on synovial biopsy.
Distinguishing Feature
In lymphoma, LAP is homogeneous soft tissue density (30-50 HU), enhancing, wall thickening >2 cm, aneurysmal dilatation; in Whipple's, LAP is markedly low-density (-10 to +20 HU, fat-containing), minimal enhancement, milder wall thickening. Density measurement is the most critical distinguishing criterion.
Distinguishing Feature
TB shows rim-enhancing LAP (central necrosis 20-40 HU), ileocecal predilection, cecal contraction, peritoneal involvement; Whipple's shows low-density fat-containing LAP (-10 to +20 HU), jejunal predilection, no cecal contraction. The rim pattern of TB LAP is distinctly different from the homogeneous low-density pattern of Whipple's.
Distinguishing Feature
In celiac disease, jejunoileal fold reversal (jejunal folds decrease, ileal folds increase), splenic atrophy, cavitating mesenteric LAP; in Whipple's, jejunal fold increase (no reversal), normal spleen, fat-containing low-density LAP (no cavitation). Fold reversal pattern is specific for celiac.
Distinguishing Feature
Metastatic LAP is soft tissue density (30-60 HU), enhancing, may be heterogeneous; Whipple LAP is low-density (-10 to +20 HU), minimal enhancement, homogeneous. Known primary malignancy and multiple bowel involvement favor metastasis; jejunal predilection and arthralgia history distinguish Whipple's.
Distinguishing Feature
Radiation enteritis shows wall thickening limited to radiation field, submucosal edema (halo sign), mesenteric vascular occlusion; Whipple's has no radiation history, fat-containing low-density LAP, jejunal predilection. Overlap of radiation field with lesion localization supports diagnosis.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
specialist-referralWhipple's disease is fatal without treatment but cure is possible with appropriate antibiotic therapy. Diagnosis by duodenal biopsy (PAS-positive macrophages — foamy histiocytes accumulating in expanded lamina propria) and T. whipplei PCR. Treatment: induction — ceftriaxone 2 g/day IV 2 weeks (or meropenem), then maintenance — trimethoprim-sulfamethoxazole 160/800 mg twice daily orally for at least 1 year. Treatment duration extended for CNS involvement with CSF PCR negativity monitoring. Treatment response assessed by clinical improvement + PAS staining negativization. On CT, normalization of LAP density and regression of jejunal wall thickening reflect treatment response. Relapse risk is 10-30% with CNS being the most serious relapse form. Gastroenterology and infectious disease consultation is mandatory.
Whipple's disease is cured with long-term antibiotic therapy (trimethoprim-sulfamethoxazole). It may be fatal if untreated. Diagnosis is by endoscopic biopsy (PAS-positive macrophages) and PCR.