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Psoriatic Arthritis — SCE Rheumatology MCQ

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ModerateMusculoskeletal ImagingPsoriatic ArthritisSCE Rheumatology

A hand radiograph from a patient with psoriatic arthritis shows erosive tapering of the distal end of the middle phalanx at a DIP joint, which sits within an expanded, cup-shaped base of the distal phalanx. Irregular fluffy periosteal new bone formation is also present. Which radiographic pattern is described?

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Correct answer: E — Pencil-in-cup deformity with periostitis

The answer is **E, pencil-in-cup deformity with periostitis**. Erosive tapering of one phalangeal end forms the “pencil”, while expansion and cupping of the adjacent phalangeal base forms the “cup”. The coexistence of erosion and periosteal new bone formation is characteristic of psoriatic arthritis and is particularly associated with advanced destructive disease, including arthritis mutilans. Marginal erosions may occur in inflammatory arthritis but do not describe the reciprocal pencil-and-cup remodelling; prominent periarticular osteopenia would favour rheumatoid arthritis. Chondrocalcinosis suggests calcium pyrophosphate deposition, while osteophytes and subchondral sclerosis are predominantly degenerative features.

Reference: Crespo-Rodríguez AM et al. Role of diagnostic imaging in psoriatic arthritis: how, when, and why. Insights into Imaging. 2021;12:121. https://pubmed.ncbi.nlm.nih.gov/34432145/