On occasion, an adult comes to my clinic for evaluation of one issue and a previously unrecognized issue is identified. This type of presentation can come in different varieties and, due to my particular practice type, often we find a birth anomaly that has not been recognized or treated. This patient is one very interesting example. She has a left hypoplastic thumb. There is an appearance difference and a functional difference yet it has not caused major problems for her. Her right thumb and hand are dominant and the left hand and thumb are used for assist (as we all function). Her thumb is weaker and more lax and has decreased motion. But none of these problems were completely troubling to her and she certainly is not interested in treatment at this point.
From the hand surgeon perspective, she has a classic small thumb on the right (technically a hypoplastic thumb– Type IIIA). It is thin (and seems long but that is really only because it is thin). She has small muscles at the base of the thumb (thenar muscles), a decreased web space (between the index and thumb), laxity at her MCP joint, and decreased thumb motion. In other words, she checks all the boxes for a classic hypoplastic thumb.
These videos demonstrate many of these classic findings for hypoplastic thumb and hopefully are helpful to better demonstrate the limitations of her left thumb. While I see many children with this condition, it is a little bit more tricky to capture the presentation on video!