Abstract
DRAM2-associated retinopathy is a rare inherited retinal dystrophy, and its outcome has not been determined. A single retinal involvement by a mutation of the DRAM2 gene is unexplained. We found three unrelated patients with a disease-causing DRAM2 variant in a biallelic state from 1555 Japanese individuals of 1314 families with inherited retinal dystrophy. We reviewed their medical records and examined their peripheral lymphocytes by transmission electron microscopy (TEM). Patient 1 was a 38-year-old woman who complained of night blindness and reduced vision. She developed macular degeneration at age 43 years. Patients 2 and 3 were a man and a woman both of whom noticed night blindness in their 30s. Both had a degeneration in the macula and midperiphery in their 40s, which progressed to a diffuse retinal degeneration in their 60s when their vision was reduced to hand motions. Three novel DRAM2 variants were identified. TEM of the lymphocytes of Patients 1 and 2 showed abnormal structures in 40.6% and 0.3% of the peripheral lymphocytes, respectively. We concluded that the DRAM2-associated retinopathy of our patients was a progressive rod-cone dystrophy, and the visual outcome was poor. The systemic effect of DRAM2 mutations may be compensable and have variations.
Highlights
DNA-damage regulated autophagy modulator 2 (DRAM2; MIM #613360; GenBank NM_178454.4) is known as transmembrane protein 77 (TMEM77)
The DRAM2 gene is located at locus 13.3 on the short arm of chromosome 1 and encodes a 266-amino acid transmembrane protein, which plays a role in autophagy induction [1,2] and tumor suppression [3]
This study aimed to determine the clinical course of three patients with DRAM2-associated retinopathy at an advanced stage of the retinopathy and to present the effects of the DRAM2 variants on the peripheral lymphocytes, determined by transmission electron microscopy (TEM)
Summary
DNA-damage regulated autophagy modulator 2 (DRAM2; MIM #613360; GenBank NM_178454.4) is known as transmembrane protein 77 (TMEM77). An autosomal recessive cone-rod dystrophy with macular involvement is reported as DRAM2-associated retinopathy (CORD21) [5,6,7,8]. It is a rare inherited retinal dystrophy, and only 21 patients in 10 families have been reported [5,6,7,8]. The findings at the advanced stage of DRAM2-associated retinopathy have not been reported, and a single retinal involvement by a mutation of the DRAM2 gene is unexplained
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