Periprosthetic collagen deposition around the proximal interphalangeal joint is a rare, non-inflammatory collagen deposition disorder that occurs mainly in adolescent males and is characterized by non-inflammatory enlargement around the proximal interphalangeal joint. The disease has not been reported globally cumulatively, and six cases were first reported in China by Ye Shannon et al. in 2005. The disease predominantly affects adolescent males, but there is also a small proportion of female patients. It is characterized by non-inflammatory enlargement around the proximal interphalangeal joints, and the involved phalanges are usually II, III, and IV fingers, with a small percentage of single-joint involvement and a special type of terminal fingertip involvement. The histopathological features are a large number of collagen fibers deposited in the dermis, without any obvious fibroblast proliferation or inflammatory cell infiltration, and the collagen fibers isolated are mainly collagen types I, III and V, which are different from the normal skin. Ultrasound, X-ray or MRI examination of the affected finger only indicated soft tissue enlargement, without bone or joint changes or inflammatory exudation in the joint space. The pathogenesis of the disease is unclear, and repeated microtrauma is one of the possible hypotheses. The disease was once thought to be a specific type of fibromatosis, but no significant fibroblast proliferation or inflammatory cell infiltration was seen locally in the lesion, except for massive collagen fiber deposition. We report two cases with characteristics consistent with those of the six cases reported by Ye Shann et al. They were male patients with symmetrical swelling of the PIP in both hands without pain or morning stiffness, and no abnormalities in laboratory and imaging examinations. This disease usually does not involve the distal interphalangeal joints and other joint sites, and the swelling or enlargement of the joints is mainly on both sides of the joints, rarely affecting the extensor surfaces of the joints, and does not involve the palmar surfaces of the joints, thus presenting a “flattened” appearance of the joints. In addition to the dermatologically related knuckle pads, foreign body granulomas, fibromas, keratosis-like elastosis, periosteal hyperplasia, and cerebral gyrus-like fibrous hyperplasia, the differential diagnosis should also be differentiated from rheumatoid arthritis, osteoarthrosis and other rheumatic diseases involving PIP, Thiemann’s disease, especially juvenile chronic arthritis, and thyroid extremity lesions, to avoid Misdiagnosis and mistreatment. Since the disease is benign in nature, no special treatment is often required. Topical hormone therapy is ineffective, and the effect of local hormone injections is not certain.