Mediterranean spotted fever is a tick-borne disease that is endemic in the Mediterranean basin from spring to autumn. Usually mild, the disease can be severe in some cases, especially when risk factors are encountered in patients or when treatment is delayed. The correlation between these malignant forms and patients' immunological disorders remains unclear, while the pathophysiology of the disease seems well known. A case of a malignant form of Mediterranean spotted fever is reported which occurred 2 months prior to the diagnosis of polymyalgia rheumatica. Evidence of immunological disorders consisted only in an antiphospholipid antibody associated with a transient lupus anticoagulant. No underlying risk factors other than the primary undiagnosed phase of polymyalgia rheumatica has been observed.