Distal phalangeal creases--a distinctive dysmorphic feature in disorders of the RAS signalling pathway?

We have observed unusual transverse distal phalangeal creases in two patients, one with Costello syndrome (G12S mutation in the HRAS gene) and one with cardio-facio-cutaneous (CFC) syndrome or possibly Noonan syndrome (Q22E mutation in the KRAS gene). This feature along with fetal pads was present in both children at birth and has persisted until age two years. Distal phalangeal creases, when present, may be a good diagnostic handle for syndromes belonging to the RAS signalling pathway.