Summary
Mitochondrial disorder | Features |
Ataxia neuropathy syndromes | Sensory ataxia, neuropathy, dysarthria, ophthalmoplegia (SANDO). May also have epilepsy and myopathy. |
Chronic progressive external ophthalmoplegia | External ophthalmoplegia, bilateral ptosis. May also show mild proximal myopathy. |
Kearns-Sayre syndrome | Early onset (< 20 years) progressive external ophthalmoplegia, pigmentary retinopathy, and one of: cerebellar ataxia, heart block, CSF protein >1g/L. Other associations: bilateral deafness, myopathy, dysphagia, diabetes mellitus, hypoparathyroidism, and dementia. |
Leigh syndrome | Infantile onset of subacute relapsing encephalopathy with cerebellar/brain stem signs. Also associated with basal ganglia lucencies and maternal history positive. |
Leber's hereditary optic neuropathy | Subacute bilateral painless visual failure in young men (M:F 4:1, median age 24). Associated with dystonia and cardiac pre-excitation syndromes. |
MEMSA (myoclonic epilepsy, myopathy, sensory ataxia) | Seizures, cerebellar ataxia, and myopathy. Associated with dementia, peripheral neuropathy, and spasticity. |
NARP (neurogenic weakness with ataxia and retinitis pigmentosa) | Late-childhood or adult onset peripheral neuropathy, ataxia and pigmentary retinopathy. Associated basal ganglia lucencies and sensorimotor neuropathy. |
MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) | Commonest mitochondrial disorder. Presents with stroke-like episodes in those < 40 years old, seizures and/or dementia, and lactic acidosis. Associated with diabetes mellitus, cardiomyopathy, bilateral deafness, pigmentary retinopathy, and cerebellar ataxia. |
MERRF (myoclonic epilepsy with ragged-red fibers) | Myoclonus, seizures, cerebellar ataxia and myopathy (ragged-red fibers on biopsy). Associated with dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity, and multiple lipomata. |
Alpers-Huttenlocher syndrome | Hypotonia, seizures, liver failure with/without renal tubulopathy. |
See: MELAS
Kearns-Sayre syndrome
Definition
- Onset before the age of 20,
- Chronic progressive external ophthalmoplegia (CPEO; mitochondrial myopathies)
- Ptosis
- Paralysis of the extraocular muscles (ophthalmoplegia).
- Pigmentary retinopathy
- Due to
- Migration of retinal pigment epithelial (RPE) cells or macrophages containing melanin into the retina.
Pathology
- Deletions in mitochondrial DNA (mtDNA) → Electron transport chain protein not made → reduce aerobic respiration → high energy tissue affected most
- Eyes
- Muscle
- Heart
- Muscle fibers stains demonstrate ragged red fibers like in other mitochondrial myopathies.
- Atrophy of the
- Retinal pigment epithelium
- Outer retina
- Aberrant pigment in all layers of the sensory retina most marked posteriorly
- In contrast to the preservation of peripheral retinal rods and cones.
- This pattern of photoreceptor degeneration led to the theory that the primary defect producing the retinopathy of KSS is in the retinal pigment epithelium.
Clinical Presentation
- Main
- Ophthalmoplegia
- Pigmentary retinopathy
- Complete heart block
- Others
- Cerebellar ataxia
- Dementia
- Deafness
- Short stature
- Endocrine disturbance.
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