To the Editor We previously reported in JMG one case of Knobloch syndrome (KS), offspring of first cousin parents with no detectable mutation in COL18A1. By autozygosity mapping and exome sequencing, we discovered a mutation in ADAMTS18, which we concluded to be probably pathogenic and indicative of locus heterogeneity in KS.1 With this letter, we wish to correct the record by reporting that the case was, indeed, due to a mutation in COL18A1.

KS is an autosomal recessive ocular disorder that is often associated with occipital defects (MIM 267750). The ocular phenotype tends to be highly characteristic and involves both the anterior and posterior segments. Typical eye findings include ectopia lentis, cryptless irides, high myopia and a distinctive vitreoretinal atrophy consisting of diffuse very severe retinal pigment epithelium atrophy with prominent choroidal vessel showing, macular atrophy with or without geographic atrophyand white fibrillar vitreous condensations.2 Occipital defects, ranging from encephalocele to mild occipital cutis aplasia, were formerly considered a requirement for …