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Understanding how primary congenital glaucoma (PCG) occurs may be a little closer now that the phenotype of the P4501B1 (CYP1B1) gene mutation in Japanese infants has been determined.
A case series of 32 infants, all but one with sporadic PCG, was tested for CYP1B1 gene mutations: 11 had mutations in both alleles, the others had none. The defining features of those with the mutation were early onset of the condition (1.7 v 3.1 months) and lower male:female ratio (6:5 v 19:2). Typical signs and symptoms were present regardless of mutation status; most infants had opacity of the cornea and many had ruptures in Descemet’s membrane. Nearly all those with the mutation and 87% of those without had disease in both eyes.
Four cases with the mutation were special. One had a unique phenotypic trait which may point to a new classification of PCG in infants based on whether the CYP1B1 mutation is present or not. Another was a compound heterozygote with C313OT mutation, whose late presentation suggests that this mutation affects P4501B1 expression. Compound heterozygotic identical twins with Ala330Phe and Val364Met mutations showed discordance in visual acuity, maybe indicating an environmental influence.
DNA from leucocytes was used to screen for CYP1B1 mutations by PCR amplification and single strand conformational analysis followed by DNA sequencing. Clinical features at onset of the condition were compared from the hospital notes in each case.
PCG is rare and occurs at very different frequencies in different ethnic populations. In Japan most cases are sporadic.
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