Schnyder corneal dystrophy (SCD) is a rare, autosomal dominant inherited corneal disorder with high penetrance that affects the central and peripheral cornea and is characterized by cholesterol and phospholipid deposition. Those depositions are mainly localized in the corneal epithelium and stroma, and in some cases, the endothelium is involved leading to progressive corneal opacity [1,2]. Corneal crystals which are present only in 54% of SCD patients can facilitate the disease diagnosis [3]. This report documented a Chinese SCD family and further clarified its ocular phenotypes. In this study, we also clarified image features of SCD by IVCM.

After informed consent, five affected individuals from a Chinese SCD family were examined and their clinical features were recorded. Three adults among them also received IVCM examination. SCD diagnosis was based on clinical manifestations and genotype analysis of UBIAD1 gene.

In vivo corneal confocal microscopy examination

IVCM [Heidelberg Retina Tomograph III with Cornea Module (HRT III/CM)] was performed on three affected individuals with SCD. Longitudinal resolution of HRT III/CM is 1 μm. A 670 nm diode laser as the light source was applied in HRT III/CM. Before the examination, one drop of topical anesthesia of 0.5% proparacaine hydrochloride (Alcaine, Alcon) was instilled in both eyes. After applying a large drop of contact gel (Berlin, Germany Subsidiary of Bausch and Lomb) on the front surface of the microscope lens. Then, the cornea was accurately examined layer by layer using IVCM.

Genetic analysis

After obtaining informed consent, blood samples were collected (5 ml of blood in EDTA) from the available family members for a molecular genetic analysis. We extracted genomic DNA from peripheral blood leukocytes according to standard procedures. Exons 1 and 2 of UBIAD1 were amplified by polymerase chain reaction (PCR) using a 25 μl reaction mixture, containing 10× PCR buffer solution (2.5 μl), 2.5 mM dNTPs mixture (2 μl), 50 mM MgCl2 (0.75 μl), forward (5 μM) and reverse (5 μM) primers (1 μl each), Platinum® Taq polymerase (0.2 μl) obtained from Invitrogen Biotechnology Co. Ltd (Shanghai, China), sterile distilled water (16.55 μl) and DNA template (1 μl). Primers for the two coding exons of UBIAD1: 1F-CTC GTG GGG TGT AAG ACC CAC TT, 1R-GCG GCT TAA ATT AGA AAG CCA CCT; 2F-AGT GCC CAC CTG CAC AGT CTA AG, 2R-CAA ACT GGG CAG CTC CTT TAC AA. The target DNA regions were amplified with the following PCR settings: initial 5 min denaturation step at 94°C and a final 5 min extension step at 72°C with an intervening 30 cycles of 30 s denaturation at 94°C, 30 s annealing at 55°C and 30 s extension at 72°C; the samples were maintained at 4°C until use (PCR Amplifier using ABi9700). Amplicons were evaluated using agarose gels and then sequenced on a 3730XL DNA Analyzer.