Syndromic presentations of mitochondrial disorders
What are the main syndromic presentations of mitochondrial disorders and why are they important?
Manifestations of mitochondrial disease can occur in virtually any organ system.
The clinical variability of these disorders can present a significant diagnostic challenge. Patients may demonstrate combinations of features that defy easy classification into known syndromes.
However, knowledge of recognized clinical syndromes found in mitochondrial disease can aid in the recognition of both common and less unusual presentations.
Some of the main presentations of mitochondrial disease are discussed in the below table.
Selected Neurologic and Nonneurologic Manifestations in Common Clinical Presentations of Mitochondrial Diseases
| Syndrome | Neurologic Phenotypes | Nonneurologic Phenotypes |
|---|---|---|
| Encephalopathy (MELAS; MERRF) | Dementia, epilepsy, myoclonus, stroke-like episodes, cerebellar ataxia | Lactic acidosis, pigmentary retinopathy, deafness, cardiac conduction defects, mild proximal weakness, diabetes mellitus, short stature |
| Myopathy (including exercise intolerance, myalgia, and myoglobinuria) | Mild to moderate limb girdle weakness | |
| PEO/PEO+/KSS | Insidious onset of ptosis and partial ophthalmoplegia, often asymmetric. Elevated CSF protein and ataxia (KSS) | |
| Mitochondrial neurogastrointestinal encephalopathy | PEO, demyelinating neuropathy, leukoencephalopathy | Hearing loss, progressive gut hypomotility, and cachexia |
| Leigh’s syndrome | Early-onset loss of motor and verbal milestones, ataxia, emesis, strokes, elevated CSF lactate | Lactic acidosis, deafness |
| Neurogenic muscle weakness, ataxia, retinitis pigmentosa | Proximal neurogenic muscle weakness, sensory neuropathy, ataxia, learning difficulties, seizures | Pigmentary retinopathy |
| Leber’s hereditary optic neuropathy | Subacute, usually painless optic neuropathy; occasionally dystonia, ataxia, neuropathy | Usually young adult males |
| Maternally inherited diabetes and deafness | Minimal or no other features | Minimal or no other features |
| Pediatric disease affecting multiple organ systems | Short stature, failure to thrive, anemia, cardiomyopathy, renal tubular acidosis |
MELAS, Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes; MERRF, myoclonic epilepsy and ragged red fibers; PEO, progressive external ophthalmoplegia; KSS, Kearns–Sayre syndrome; CSF, cerebrospinal fluid.
