Tropheryma whipplei , Immunosuppression and Whipple's Disease: From a Low-Pathogenic, Environmental Infectious Organism to a Rare, Multifaceted Inflammatory Complex.

BACKGROUND: The actinobacterium Tropheryma whipplei was detected 20 years ago by molecular techniques, and following its culture has been characterized as the cause of a systemic infection known as Whipple's disease (WD). T. whipplei occurs in the environment, is prevalent only in humans, is believed to be transmitted via oral routes and to be host dependent.

KEY MESSAGES: The classical form of T. whipplei infection, i.e. classical WD (CWD), is rare. It is well defined as slowly progressing chronic infection with arthralgia, diarrhea and weight loss, mostly in middle-aged men. However, current research revealed a much broader spectrum of clinical features associated with T. whipplei infection. Thus, T. whipplei may cause acute and transient infections (observed primarily in children) and the bacterium, which is found in soil and water, occurs in asymptomatic carriers as well as in CWD patients in clinical remission. In addition, T. whipplei affects isolated and localized body compartments such as heart valves or the central nervous system. Subtle immune defects and HLA associations have been described. New findings indicate that the progression of asymptomatic T. whipplei infection to clinical WD may be associated with medical immunosuppression and with immunomodulatory conditions. This explains that there is a discrepancy between the widespread occurrence of T. whipplei and the rareness of WD, and that T. whipplei infection triggered by immunosuppression presents with protean clinical manifestations.

CONCLUSIONS: This review highlights recent findings and the clinical spectrum of infection with T. whipplei and WD, focusing specifically on the role of host immunity and immunosuppression. Current concepts of the pathogenesis, diagnosis and therapy are discussed.