Whipple's disease (WD) is a rare multisystemic infectious disease caused by Tropheryma whipplei. The pathogenesis of Whipple's disease remains unknown and clinical experience relies solely on various case reports published in the literature. The disease may occur at any age, with most studies describing patients in their fifth decade. Classic WD mainly affects the gastrointestinal tract, but extraintestinal commitment can occur, with the most common manifestations being arthralgias, lymphadenopathy, fever, and neurological symptoms. We present a case of a 69-year-old woman who presented with fever, macular rash, abdominal pain, lymphadenopathy, pleural and pericardial effusion, weight loss, and severely altered mental status over seven days. Initial workup tests only revealed leucopenia, thrombocytopenia, and hyperferritinemia. Since the fever persisted despite antibiotic treatment, an extensive workup was required until the final diagnosis of classic WD through histological examination of duodenal biopsies. Treatment with ceftriaxone was implemented for two weeks, followed by trimethoprim-sulfamethoxazole 160/800mg bid for 12 months. The patient presented full recovery and no recurrence after three years of follow-up. Even though WD was first described more than a century ago, WD is an elusive disease with a wide variety of clinical findings, leading to a still significant delay in diagnosis. WD should be considered in the differential diagnosis of rheumatologic disorders, chronic abdominal pain or diarrhea, neurological manifestations not suggestive of any other specific disease, non-caseating granulomatous diseases, and cases of lymphadenopathies. The authors aim to add additional clinical data and raise awareness for a rare condition that can be lethal if not timely treated. More studies and recommendations are needed concerning screening patients and treatment, with an urgent need to improve the delay in diagnosis.