Task: Question Answering
Input (English): Context: Infections generally occur in intravenous drug abuse (IVDA) patients, most commonly affecting the spine and proximal joints. Numerous serious musculoskeletal complications of IVDA may involve the upper extremity, however. Soft-tissue complications in the upper extremity of IVDA patients include cellulitis, ulceration, abscess, pyomyositis, septic bursitis, tenosynovitis, and necrotizing fasciitis. Foreign bodies in soft tissue due to needle fragments are common findings. Primary bone and joint IVDA complications include osteomyelitis (acute and chronic) and septic arthritis. Other IVDA complications in the upper extremity affecting blood vessels and lymphatics include hematoma, arterial aneurysm and pseudoaneurysm, thrombosis, thrombophlebitis, "puffy hand" syndrome, and lymphadenopathy. These complications usually present as urgent issues requiring prompt and accurate evaluation in the acute setting. Diagnostic imaging not only aids in making the correct diagnosis but also permits precise definition of the location and extent of these abnormalities. We review the imaging findings and illustrate a wide range of disabling and even life-threatening complications affecting the upper extremity of IVDA patients that require early diagnosis for optimal outcome. 
 Question: What causes "Puffy hand syndrome"?
Output (English): intravenous drug abuse