Syndromic craniosynostosis, fibroblast growth factor receptor 2 (FGFR2) mutations, and sacrococcygeal eversion presenting as human tails.

INTRODUCTION: There have been 23 previously published cases of patients with syndromic craniosynostosis and human tails. In many of these, the tail was composed of prominent coccygeal and sacral vertebrae, curved in a retroverted instead of in the normal anterograde fashion. This has been termed sacrococcygeal eversion. In those cases in which genetic testing results are reported, there were fibroblast growth factor receptor 2 (FGFR2) mutations.
METHODS: We present three patients with Pfeiffer syndrome and sacrococcygeal eversion. Two had genetic testing and both had FGFR2 mutations, one of them a novel mutation in patients with syndromic craniosynostosis and sacrococcygeal eversion. We also briefly review the literature on craniosynostosis and human tails.
RESULTS: All but one reported patient has had either Pfeiffer, Crouzon, or Beare-Stevenson syndrome. Most patients, including ours, have had severe manifestations of their syndrome. Although the pathogenesis of sacrococcygeal eversion is unknown, a similarly posteriorly curved tail bud develops in normal human embryos during the second month of gestation.
CONCLUSIONS: Perhaps increased FGFR2 activation during this embryonic period leads to abnormal differentiation or regression of the tail bud and, in turn, sacrococcygeal eversion, in certain patients with severe syndromic craniosynostosis.