Murderer’s thumb is one name for brachydactyly, type D. The is a short, round distal phalanx of the thumb and may be one on side or both. The nail looks wide relative to the overall length of the thumb. Other common names include stub thumb and club thumb (not to be confused with the medical condition of clubbing). Good additional information can be found on OMIM.
The condition is associated with the HOXD13 gene. Conditions which affect the entire HOXD gene lead to more severe deficiencies of the upper extremity. This is classically inherited in an autosomal dominant fashion which means 50% of children of a parent with this condition will also have this thumb anomaly.
Treatment is rarely if ever indicated. This is an appearance issue but function is typically normal although some may describe some difficulty with activities that require major thumb bending (i.e., thumb IP joint flexion), including texting.
Murderer’s thumb is one type of brachydactyly. Brachydactyly means ‘short finger’ (from Ancient Greek) and there are a large number of different brachydactylies. Most are quite rare but Type D is one of the more common types, estimated at 2% incidence. There are a wide variety of brachydactylies and these should not be confused with symbrachydactyly (short finger with syndactyly). Type E is also common and has been the source of previous posts on this blog.
Murderer’s thumb is a rare condition with a short, rounded distal phalanx of the thumb. It rarely requires treatment as it is primarily just a difference in appearance.