Review Question - QID 218077

A 2-year-old male presents to clinic with his mother for initial evaluation of bilateral upper extremity deformity. No formal diagnosis has been made at this time, but the patient was diagnosed with an atrial and ventricular septal defect shortly after birth. Recent genetic analysis demonstrates that the patient has a mutation in the gene for the transcription factor TBX5. The mother states she was born without thumbs, and that the patient’s sister has a similar deformity affecting her right upper extremity. There are no other abnormalities noted on physical exam. A radiograph of the patient’s forearms is demonstrated in Figure A. What is the most likely diagnosis?