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COMMENTARY
Year : 2020  |  Volume : 68  |  Issue : 1  |  Page : 253

Commentary: Heteroplasmy in maternally inherited diabetes and deafness


Department of Vitreoretina and Uveitis Services, L V Prasad Eye Institute, Visakhapatnam, Andhra Pradesh, India

Date of Web Publication19-Dec-2019

Correspondence Address:
Dr. Bhavik Panchal
Department of Vitreoretina and Uveitis Services, L V Prasad Eye Institute, Visakhapatnam - 530 040, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_1296_19

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How to cite this article:
Panchal B, Saoji K. Commentary: Heteroplasmy in maternally inherited diabetes and deafness. Indian J Ophthalmol 2020;68:253

How to cite this URL:
Panchal B, Saoji K. Commentary: Heteroplasmy in maternally inherited diabetes and deafness. Indian J Ophthalmol [serial online] 2020 [cited 2020 Aug 5];68:253. Available from: http://www.ijo.in/text.asp?2020/68/1/253/273189



Maternally inherited diabetes and deafness (MIDD) is a mitochondrially inherited disease. Mitochondrial DNA is inherited from the mother and its defects affect organs that demand higher energy such as the eye, inner ear, central nervous system, skeletal, and cardiac muscle. MIDD is associated with early onset diabetes and sensorineural deafness. The various other systemic features reported include cardiomyopathy, renal problems, and neuropsychiatric symptoms. Pigmentary retinal dystrophy is the most common ophthalmic manifestation.[1]

The prevalence of MIDD ranges from 0.5% to 2.8%.[2] MIDD has been reported to be associated with mutations, such as MT-TL1 and MT-TK of which MT-TL1 is the most common.[3] Tripathy K et al. have noted A3243G mutation in MT-TL1 gene using Sanger sequencing in one of their subject.[4] The A3243G mitochondrial mutation is seen with a wide range of mitochondrial encephalomyopathies including MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke) or MELAS/MERRF (myoclonic epilepsy, red ragged fibers) overlap syndrome.[5] However, the same mutation can cause different phenotypes. The phenotypic variability is determined by the degree of heteroplasmy.[6] The authors too noted a difference in the phenotypes within the family members and related it to heteroplasmy.

Heteroplasmy is the presence of more than one type of organellar genome (mitochondrial DNA or plastid DNA) within a cell or individual. It is an important factor in considering the severity of mitochondrial diseases. The most frequent findings in A3243G mutation-positive participants was hearing loss and macular disturbance, with 95% of mutation-positive relatives having hearing loss.[5] Macular disturbance is in the form of a pattern dystrophy - an important clinical sign in the diagnosis of MIDD. There are three grades for this manifestation: Grade 1: Severe punctate pigment dots in the macula; Grade 2: A butterfly or reticular pattern; and Grade 3: Multifocal or a continuous perifoveal atrophy of the RPE.[5],[6],[7],[8] The variability of the manifestations could be attributed to the heteroplasmy in MIDD.

Financial support and sponsorship

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Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Smith PR, Bain SC, Good PA, Hattersley AT, Barnett AH, Gibson JM, et al. Pigmentary retinal dystrophy and the syndrome of maternally inherited diabetes and deafness caused by the mitochondrial DNA 3243 tRNA (Leu) A to G mutation. Ophthalmology 1999;106:1101-8.  Back to cited text no. 1
    
2.
Massin P, Virally-Monod M, Vialettes B, Paques M, Gin H, Porokhov B, et al. Prevalence of macular pattern dystrophy in maternally inherited diabetes and deafness. GEDIAM Group. Ophthalmology 1999;106:1821-7.  Back to cited text no. 2
    
3.
Van den Ouweland JMW, Lemkes HPJ, Ruitenbeek W, Sandkuijl LA, de Vijlder MF, Struyvenberg P, et al. Mutation in mitochondrial tRNA (leu-UUR) gene in a large pedigree with maternally transmitted type II diabetes mellitus and deafness. Nature Genet 1992;1:368-71.  Back to cited text no. 3
    
4.
Tripathy K, Sarma B, Mazumdar S. Outer retinal tubulation and inner retinal pseudocysts in a patient with maternally inherited diabetes and deafness evaluated with optical coherence tomography angiogram. Indian J Ophthalmol 2020;68:250-3.  Back to cited text no. 4
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5.
Michaelides M, Jenkins SA, Bamiou DE, Sweeney MG, Davis MB, Luxon L, et al. Macular dystrophy associated with the A3243G mitochondrial DNA mutation. Distinct retinal and associated features, disease variability, and characterization of asymptomatic family members. Arch Ophthalmol 2008;126:320-8.  Back to cited text no. 5
    
6.
Rath PP, Jenkins S, Michaelides M, Smith A, Sweeney MG, Davis MB, et al. Characterisation of the macular dystrophy in patients with the A3243G mitochondrial DNA point mutation with fundus\autofluorescence. Br J Ophthalmol 2008;92:623-9.  Back to cited text no. 6
    
7.
Ambonville C, Meas T, Lecleire-Collet A, Laloi-Michelin M, Virally M, Kevorkian JP, et al. Macular pattern dystrophy in MIDD: Long-term follow-up. Diabetes Metab 2008;34:389-91.  Back to cited text no. 7
    
8.
Agarwal A. Heredodystrophic disorders affecting the pigment epithelium and retina. In: Agarwal A. editor. Gass' Atlas of Macular Diseases. Edinburgh, New York: Elsevier/Saunders; 2012. p. 272-3.  Back to cited text no. 8
    




 

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