The disease is common in farmers and those exposed to soil and animals, suggesting that the infection is acquired from these sources.Individuals who are most susceptible to the disease are those with decreased ability to perform intracellular degradation of ingested pathogens or particles, particularly within macrophages. Several studies indicate that defective T-lymphocyte (particularly TH1 population) function may be an important predisposing factor for the disease. In particular, circulating cells which are CD11b (also known as integrin alpha) expressive are reduced in susceptible individuals. CD11b has a vital role in activation of macrophages to destroy intracellularly ingested T. whipplei bacteria. Diagnosis
Common clinical signs and symptoms of Whipples disease include diarrhea, steatorrhea, abdominal pain, weight loss, migratory arthropathy, fever, and neurological symptoms. Weight loss and diarrhea are the most common symptoms that lead to identification of the process, but may be preceded by chronic, unexplained, relapsing episodes of nondestructive seronegative arthritis, often of large joints.Endoscopy of the duodenum and jejunum can reveal pale yellow shaggy mucosa with erythematous eroded patches in patients with classic intestinal Whipples disease, and small bowel X-rays may show some thickened folds. Other pathological findings may include enlarged mesenteric lymph nodes, hypercellularity of lamina propria with "foamy macrophages", and a concurrent decreased number of lymphocytes and plasma cells, per high power field view of the biopsy.Diagnosis is made by biopsy, usually by duodenal endoscopy, which reveals PAS-positive macrophages in the lamina propria containing nonacid-fast, Gram-positive bacilli.
Chronic malabsorptive diarrhea leads to the poor absorption of fat, causing steatorrhea (fatty, offensive-smelling stool), flatulence, and abdominal distension. Protein-losing enteropathy may also occur, causing depletion of albumin, a blood protein, which may lead to peripheral edema caused by the lowered oncotic pressures.Hyperpigmentation of the skin occurs in almost half; some also have skin nodules. Various eye problems, such as uveitis, may occur; this is typically associated with deteriorating vision and pain in the affected eye. Endocarditis (infection of the heart valve) has been reported in a small number of cases, sometimes in people with no other symptoms of Whipples disease; this is typically noticed as breathlessness and leg swelling due to fluid accumulation as the heart is unable to pump fluid through the body.Of those affected by Whipples disease, 10–40% have problems related to the involvement of the brain; the symptoms relate to the part of the brain that is affected. The most common problems are dementia, memory loss, confusion, and decreased level of consciousness. Eye-movement disturbances and myorhythmia (rapidly repetitive movements of the muscles) of the face, together referred to as oculomasticatory myorhythmia, are highly characteristic for Whipples disease. Weakness and poor coordination of part of the body, headaches, seizures, and a number of more uncommon neurological features are present in some cases. Mechanism
T. whipplei is one of the Actinomycetes, and is a distant relative of the Mycobacterium avium complex, explaining in part why Whipples disease is similar to the diseases caused by MAC bacteria.