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.
Genetics
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.
Murderer’s Thumb
Treatment
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.
Brachydactyly
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.
Summary
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.
Nice to know what this is called as both of my thumbs have it but it’s more pronounced on the left. Neither of my siblings have it and neither did my parents but my mom always said her dad did. Can that happen that it skips a generation?
Thanks Kathy. The genetics can be unpredictable and can certainly change. While skipping a generation is not common, it certainly may be your scenario.