Simian Crease in DS

[Soumen Barua]

I was reading articles online on Down Syndrome last few days. One of the issue that was striking was the presence of simian line among down syndrome patients. Although this simian crease is present among normal population without any incidence of DS. Having said that it occurred to me that maybe the presence of Simian Crease is not a marker of DS instead the absence of other creases on the palm are marker of DS. For example DS patients have weak Thenar crease. These palms do not have great many variations as far as palm lines are concerned and most are missing many lines. Just few major lines (including simian crease) and few others but what about so many other small lines among DS patients? They are all missing and maybe that's more significant in DS than trying to associate DS with simian crease. More research needs to be done and almost all are focused on presence of simian crease on DS palm as well as associate Simian Crease with other chromosomal anomalies. Lots of people with simian crease have genius level intelligence not to mention many ethnic groups have strong occurrence of Simian crease among the population.
My hunch is Simian crease among DS is formed by incomplete distal and proximal line. I believe there are Simian (type A), Sydney (type B) and neither or incomplete (type C) lines. Maybe type C is more prevalent in DS (citation) and incomplete distal starting below little finger and incomplete proximal starting between index and thumb finger meets at middle giving an appearance of one big line or Simian crease. This is just a theory and I can not prove it but hypotonia and poor grasp is common sympton of DS.
Lastly, how hypoplasia of little finger effects the formation of these lines, very little research has been done on that topic, for example weak thumb will result in almost deletion of thenar crease.