Abstract
Purpose :
DMD is an X-linked recessive disorder [mutations in the dystrophin gene on chromosome Xp21.2] affecting about 1/5000 male live births. Dystrophin maintains muscle strength and participates in central nervous system [CNS] and retinal signaling. Deletion upstream to position 45 in the DMD gene results in more deleterious frameshift mutations than those downstream, which have a good amount of residual dystrophin left. A great deal of genetic and clinical heterogeneity exists in presentation. Presumptive sporadic DMD on pedigree charting is observed in about 33% cases and may be due to de novo mutations as well as maternal transmission. This cross-sectional study aimed to evaluate CV and photopic ERG as functional evidence of retinal malfunctioning in a cohort of children with presumptive sporadic [on 3 generation pedigree charting] DMD [genetic or muscle biopsy diagnosis] in a tertiary care pediatric ophthalmology centre in northern India.
Methods :
Complete ophthalmic evaluation of 19 male children [8±1.8years] with DMD, 13 diagnosed on genetic analysis and 6 on muscle biopsy, was performed. Detailed CV assessment was done with Ishihara, Hardy-Rand-Rittler {HRR}, Farnsworth and Lanthony saturated and desaturated tests and photopic ERG was performed on Metrovision MonPack One ERG module, France, 2011. The mothers were evaluated as controls.
Results :
Anterior and posterior segment ocular evaluation was normal with best corrected visual acuity [BCVA] of logMAR 0.00 in both eyes in all cases. Red-green CV deficit was present in 3 cases with all demonstrating a/b wave inversion and attenuation of b waves on photopic ERG. They had deletions in exon 17-21, 45-90 and 60 respectively. In 10 subjects with normal CV, only 1 subject with deletion in exon 46-47 had normal photopic ERG waves. In 6 subjects with biopsy proven DMD, 1 had normal photopic ERG waves while the rest showed b wave attenuation. The mothers of these children did not demonstrate any functional or structural ocular anomalies.
Conclusions :
This study, unique in the north Indian cohort, demonstrates significant attenuation of photopic ERG waves in 17/19 and red-green CV deficit in 3/19 presumptive sporadic cases of DMD irrespective of the position of exon deletion. These tests were however not useful in identifying the carrier status of the mothers, as these functions were normal in them.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.