Mitochondrial chromosomal abnormaity leads to -
Ans. is 'a' i.e., Lebers hereditary optic neuropathy o Diseases associated with mitochondrial inheritance are rare and many of them affect the neuromuscular system,o Leber hereditary optic neuropathy is a prototype of this disorder. It is a neurodegenerative disease that manifests itself as progressive bilateral loss of central vision. Visual impairment is first noted between ages 15 and 35, and it leads to blindness. Cardiac conduction defects & minor neurologic manifestations have also been seen in some families.Mitochondrial diseaseso DMA in human may be found at two locationsNuclear DNA in the nucleusOrganelle DNA in the mitochondriao Mitocondrial DNA is the only non-chrontosomal DNA in human cells.o Mitochondrial DNA, is always maternally inherited. Why is it so, lets see :-Mitochondrial and nuclear DNA are located in different places in the cell. During fertilization, the sperm and egg cell nuclei fuse to form an embryo. The egg cell is very large compared to the sperm, so although the cells' nuclei fuse, the rest of the cell mass in the embryo comes from the egg only. Nuclear DNA is therefore co-inherited but the mitochondrial DNA, which is located outside of the nucleus, is always maternally inherited because all mitochondria in a foetus and later adult are derived from the mitochondria in the mothers egg.All children from affected mother will inherit the disease but it will not be transmittedfrom an affectedfather to his children.Clinical Syndromes of Mitochondrial DiseasesDisorderPrimary FeaturesAdditional FeaturesChronic progressive external ophthalmoplegia (CPEO)o External ophthalmoplegiao Bilateral ptosiso Mild proximal myopathyKearns-Sayre syndrome (KSS)o PEO onset before age 20 yearso Pigmentaiy retinopathyo One of the following CSF protein greater than 1 g/L, cerebellar ataxia, heart blocko Bilateral deafnesso Myopathyo Dysphagiao Diabetes mellituso Hypoparathyroidismo DementiaPearson syndromeo Sideroblastic anemia of childhoodo Panytopeniao Exocrine pancreatic failureo Renal tubular defectsInfantile myopathy and lactic acidosis (fetal and non-fataJ forms)o Hypotonia in the first year of lifeo Feeding and respiratory difficultieso Fatal form may be associated with a cardiomyopathy and/or the Toni-Fanconi-Debre syndromeLeigh syndroms (LS)o Subacute relapsing encephalopathyo Cerebellar and brain-stem signso Infantile onseto Basal ganglia lucencieso Maternal history of neurologic disease of Leigh syndromsNeurogenic weakness with ataxia and retinitis pigmentosa (NARP)o Late-childhood or adult-onset peripheral neuropathyo Ataxiao Pigmentary retinopathyo Basal ganglia lucencieso Abnormal eiectroretinogramo Sensorimotor neuropathyMitochondria] encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS)o Stroke-like episodes before age 40 yearso Seizures and/or dementiao Ragged-red fibers and/or lactic acidosiso Diabetes mellituso Cardiomyopathy (initially hypertrophic: later dilated)o Bilateral deafnesso Pigmentary retinopathyo Cerebellar ataxiaMyoclonic epilepsy with ragged-red fibers (MERRF)o Myoclonuso Seizureso Cerebellar ataxiao Myopathyo Dementiao Optic atrophyo Bilateral deafnesso Peripheral neuropathyo Spasticityo Multiple lipomataLeber hereditary optic neuropathy (LHON)o Subacute painless bilateral visual failureo Males: females- 4:1o Median age of onset 24 yearso Dystoniao Cardiac pre-excitation syndromes
Lebers hereditary optic neuropathy
Angelman syndrome
Prader villi syndrome
Myotonic dystrophy
Cytogenetic Disorders