Scrotal tongue and geographic tongue: polygenic and associated traits.

The familial nature of scrotal and geographic tongue was investigated in parents and siblings of 156 probands having these conditions. The prevalence in parents and siblings was significantly higher than that in the control populations. The prevalence in sibilings from families in which at least one parent was also affected was significantly higher than that in siblings from families in which neither parent was affected. The prevalence of scrotal tongue alone in siblins was similar irrespective of the condition in the proband. The prevalence of geographic tongue alone was highest in siblins of probands having only geographic tongue. A polygenic mode of inheritance with some genes common to both conditions is suggested.