Persistence of fetal vasculature in a patient with Knobloch syndrome: Potential role for endostatin in fetal vascular remodeling of the eye

Objective To report a child with Knobloch syndrome (KS) with features of persistent fetal vasculature (PFV) and to discuss the possible role of endostatin in vascular remodeling of the fetal eye. Design Case report with enzyme-linked immunosorbent assay (ELISA) analysis of serum endostatin. Main outcome measures Ocular examination, fluorescein angiography, echography, ELISA analysis of serum endostatin, and typing for pathogenic mutations in COL18A1. Results Slit-lamp examination in the left eye disclosed numerous findings of PFV, including an extensive persistent pupillary membrane, scarcity of iris crypts, and pigmented epicapsular stellate remnants on the anterior lens surface. Dilated fundus examination revealed a total posterior vitreous detachment, despite the young age of the patient, with numerous white intragel opacities that were compatible with remnants of the vasa hyaloidea propria. The fundus had a tesselated appearance with angiographically visible large choroidal vessels. There was a retinochoroidal staphyloma inferotemporal to the optic disc. There were no retinal vessels visible temporally, and there was no macular differentiation or foveal pit. Competitive ELISA analysis disclosed no detectable serum endostatin. None of the 8 reported pathogenic mutations in the COL18A1 gene was found in the patient. Conclusions Persistent fetal vasculature may be a clinical and important manifestation in some patients with KS and can be explained by a deficiency in endostatin. Endostatin deficiency may result in reduced or delayed regression of fetal blood vessels in the eye (including the intravitreal compartment), thereby resulting in incomplete development of the normal vasculature in the retina. Our typing results for the reported COL18A1 mutations confirm the genetic heterogeneity of KS.