We report a case of arthritis, hypercalcemia, and lytic bone lesions that occurred shortly after repeated administration of recombinant hepatitis B virus (HBV) vaccine in a 44-year-old man who had had myasthenia gravis 20 years earlier. He presented with ankle and knee arthritis and hypercalcemia. Radiographs revealed small lytic lesions and densitometry showed severe osteopenia. Quantimetric bone biopsy confirmed major bone loss and showed dramatic increase in bone turnover, as well as an unusual periosteal apposition of woven bone. Short term treatment with prednisone and furosemide and longterm treatment with clodronate allowed rapid improvement. After one year, the patient remains clinically asymptomatic. Despite negative immunologic investigations to sustain the hypothesis of HBV vaccination as a causal factor, we believe the bone lesions could be attributed to unusual bone "hyperremodeling" triggered by an immune process in a predisposed individual.