CABP4 Mutations Do Not Cause Congenital Stationary Night Blindness – Corrected Proof

I read with interest the analysis of Dutch patients diagnosed with congenital stationary night blindness (CSNB) by Bijveld et al, particularly what was written regarding patients with recessive mutations in calcium binding protein 4 (CABP4; Mendelian Inheritance in Man *608965). CABP4 encodes a protein that is specifically located in photoreceptor synaptic terminals, where it probably modulates photoreceptor calcium release. Only 3 of 101 patients diagnosed with CSNB in the authors' series had CABP4 mutations, and all 3 patients (2 families) harbored the same homozygous mutation (c.646C>T; p.Arg216X). These 3 patients had nystagmus and low vision. Two were photophobic. All 3 had a normal fundus appearance and severe color deficiency. None complained of night blindness. All 3 were hyperopic. Such signs and symptoms, combined with their cone–rod dysfunction by electroretinography, should suggest a diagnosis of cone-rod disease rather than predominantly rod disease such as CSNB. However, because during scotopic flash stimulus there was an electronegative waveform, which is classically associated with CSNB, the 3 patients were labeled as CSNB2 (“incomplete CSNB,” with the “incomplete” referring to some rod function being present rather than completely absent). The authors recognized that these 3 patients had a distinct phenotype that was atypical for a diagnosis of CSNB2 and wondered whether studies of additional patients would confirm or refute their findings.