Two mutations in the TGFBI gene (A546D and P551Q) cosegregated with LCD in an extensively studied family that lacked the R124C mutation that frequently accompanies this form of corneal amyloidosis.
The incidence of mutations was ranked as follows: 118 patients (72%), the R124H mutation associated with Avellino corneal dystrophy; 23 patients (14%), the R124C mutation associated with lattice corneal dystrophy type 1; and 10 patients (6%), the P501T mutation associated with lattice corneal dystrophy type 3A.
In exon 4, an R124H mutation associated with Avellino corneal dystrophy (ACD) was found in 39/44 families (86.4%) and an R124C mutation associated with lattice corneal dystrophy type 1 (LCD1) was detected in 2/44 families (4.5%).
This study expands on our previous research investigating dystrophic stromal aggregates, with the aim of better elucidating the pathomechanism of two conditions arising from the most common TGFBI mutations: granular corneal dystrophy type 1 (GCD1; R555W) and lattice corneal dystrophy type 1 (LCD1; R124C).
To report a Japanese family diagnosed clinically as having lattice corneal dystrophy type I (LCDI) in which a Leu518Pro mutation in the betaig-h3 gene and not the R124C mutation reported previously was found.
Genomic DNA was extracted from peripheral leukocytes from six affected and three unaffected members of a family with lattice corneal dystrophy type I. Exon 4 of the transforming growth factor-induced gene (TGFBI) was screened for the most frequent mutation, R124C, in the proband by sequencing.
We identified two TGFBI mutations: R124C (exon 4), which segregated with lattice type I corneal dystrophy, and R555W (exon 12), which segregated granular type I corneal dystrophy.
The R124C mutation of the TGFBI gene gives rise to lattice corneal dystrophy type I, which is characterized by irregularity, turbulence, and opacity of the corneal epithelium.
The novel mutations c.(1702G>C and 1706T>A; p.Arg514Pro and Phe515Leu), c. 531C>T (p. Arg124Cys), c.1876A>G (p.His572Arg) in TGFBI were responsible for LCD in the 3 families.
Six patients with Avellino corneal dystrophy (ACD) associated with R124H, one patient with superficial granular corneal dystrophy (SGCD) associated with R124L, and seven patients with lattice corneal dystrophy type 1 (CDL1) associated with R124C were examined.
Spontaneous mutations were detected in 2 families: an R124C mutation in 1 family with lattice corneal dystrophy (LCD) type I and an A546D mutation in the other with atypical LCD.
Although a slit-lamp examination showed features of LCDI in most cases, the age at onset of the symptoms was several years later than that in cases of LCDI with an R124C mutation.
The fact that the 43-kDa protein fragment was present primarily in R124C and R124H but not in WT implicates its potential role in the protein deposits of LCD.