Deciphering caudal embryonic defects: embryological analysis and reviewing literature data.

BACKGROUND A number of syndromes÷associations involving the caudal region have been described in the literature. Each of them is characterized by a set of morphological features. Reports on difficulties in delineation and an ever-increasing constellation of defects in recent past call for a comprehensive study into the morphologic presentations and pathogenesis of caudal embryonic defects. MATERIALS AND METHODS The present article describes a case of the OEIS complex--a combination of omphalocele, exstrophy of bladder, imperforate anus and spinal defects. Literature search was performed and morphologic presentations, as described in literature, of all syndromes and associations affecting the caudal region of the embryo have been compared. Morphologic presentations were analyzed embryologically. RESULTS A remarkable overlap of symptom complex was observed. Embryological analysis of the phenotypic presentations of all these syndromes points towards a common pathogenesis, early in the embryonic life. The embryologic analysis suggests that these defects are a result of defects in proliferation, migration or subsequent differentiation of any of the three subdivisions of intra-embryonic mesoderm. CONCLUSIONS Based on the analysis a new hypothesis for the causation of caudal defects is proposed. This hypothesis suggests that a local internal environmental imbalance, at the site of implantation, can cause nutritional insult to the embryo during gastrulation, during the third and the early fourth week of embryonic life.