Mixed connective tissue disease

an overlap syndrome characterized by presence of a ribonuclease-sensitive extractable nuclear antigen in serum, with clinical features typical of more than one collagen disease, including systemic lupus erythematosus, scleroderma, dermatomyositis and rheumatoid arthritis.

Radiographically, alterations compatible with rheumatoid arthritis (joint erosion, joint space narrowing, periarticular osteoporosis), scleroderma (tuftal resorption, soft tissue calcification) and systemic lupus erythematosus (deforming nonerosive arthropathy) may be noted. The regions affected most commonly are the proximal interphalangeal and metacarpophalangeal joints of the hands, midcarpal and radiocarpal compartments of the wrist, and metatarsophalangeal and interphalangeal joints of the feet. In some cases the distal interphalangeal joints may also be involved. In the hands, bone resorption leads to typical pencilling of the phalanges.