Whipple's Disease; An Overlooked Diagnosis.

Whipple disease is a rare multisystem inflammatory disease. Because fewer than 1000 reported cases have been described, clinical experience with this disorder is sparse. We are reporting a case of a 46-year-old man who presented with fever, weight loss, and polyarthralgia for 2 months, and 1 month of diarrhea. The patient was thoroughly investigated for collagen diseases and COVID-19, with no definite diagnosis. A therapeutic trial by immunosuppressive drugs provided partial remission followed by a marked rebound of the symptoms. His occult blood in stool was positive and subsequent upper endoscopy with proximal small intestinal biopsies showed the pathological features of Whipple's disease. The patient showed a dramatic improvement following treatment with ceftriaxone and trimethoprim-sulfamethoxazole. Despite the rarity of Whipple's disease, its course mimics many rheumatological diseases, inflammatory bowel disease, and COVID-19 disease. It should always be a part of the differential diagnosis of obscure polyarthralgia and chronic diarrhea.