This in addition to the known impact of TCF4 abundance on fibroblast growth factor production (necessary for neuronal function) was shown [16] prompted us to investigate myofibroblasts in the muscle biopsy of our PTHS patient more detailed: co-staining of CD90 and Vimentin revealed a reduced co-immunoreactivity accompanied by the increase of areas which are solely reactive for CD90 compared to investigated controls. This evidence concerns the gene TCF4 and Pitt-Hopkins syndrome.