What do we (not) know about the human bartonelloses?

The human bartonelloses are a group of diseases with a rapidly increasing clinical spectrum. Well known manifestations such as Carrion's disease, trench fever, cat-scratch disease, and bacillary angiomatosis are examples of Bartonella sp. infection. Along with these diseases, recurrent bacteremia, endocarditis, septicemia, erythema nodosum, erythema multiforme, trombocytopenic purpura and other syndromes have been reported having been caused by bacteria of this genus. The infectious process and the pathogenesis of these microorganisms are poorly understood. The bartonelloses may have a benign and self-limited evolution in a host, or a potentially fatal one. These bacteria can provoke a granulomatous or an angioproliferative histopathologic response. As these diseases are not yet well defined, we have reviewed the four main human bartonelloses and have examined unclear points about these emergent diseases.