A 7-year-old boy presented with both of his thumbs flexed (Figure 1), the inability to perform the
‘thumbs-up’ gesture, and difficulties in opposing thumbs and fingers in activities such as holding a
pencil during writing, pincer movements, and picking up small objects. His mother only observed
the deformity for one month after the boy complained of difficulty in writing during class. He
had no prior history of trauma to the thumbs or pain and swelling in other joints. There were no
other birth anomalies noticed by his parents. Upon examination, the boy had flexion deformities
of the interphalangeal joint (IPJ) on both of the thumbs. Passive range of motion of the IPJ was
not possible and both were fixed at 60° of flexion. Power of both thumbs could not be assessed as
there was no motion of the joint. The range of motion of the metacarpophalengeal joints (MCPJ)
of both thumbs and all other finger joints was normal. A 0.5cm x 0.5cm subcutaneous nodule was
palpable at the volar crease of the MCPJ bilaterally. The nodule was tender on palpation; however,
no overlying skin changes were evident. (Copied from article).