Disappearing Foot Disease: An Unusual Presentation of Primary Lymphoma of Bone

In 1989, an 89-year-old woman was diagnosed with primary lymphoma of bone (PLB) after presenting with a painful swollen right foot, which had been worsening over a year and had severe pain in the last two months. Radiographs revealed significant bone destruction in her right mid and forefoot. Although tophaceous gout was initially suspected, a biopsy confirmed PLB. She had no signs of widespread non-Hodgkin's lymphoma and responded well to localized foot irradiation, with symptom improvement in two weeks and no recurrence after 12 months. This case was notable for the rare involvement of the foot's small bones and the patient's age. It also suggested that an absence of acute phase protein response, which usually indicates tissue inflammation, could help differentiate PLB from other inflammatory bone conditions.