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Chronic Progressive External Ophthalmoplegia
abbreviated CPEO
Compare CPEO with Congenital Fibrosis of EOM (CFEOM)
| Feature | CPEO | CFEOM |
|---|---|---|
| Nature of disorder | Mitochondrial myopathy of extraocular muscle | Congenital cranial dysinnervation disorder (neurogenic; abnormal CN III/IV/VI development with secondary muscle fibrosis) |
| Onset | Adult, typically 18–40 yrs; ptosis first sign | Congenital / present at birth |
| Course | Slowly progressive over years | Non-progressive (rare exceptions) |
| Symmetry / gaze | Generally symmetric, diffuse limitation of all directions; superior rectus often prominently involved | Fixed characteristic pattern — CFEOM1: eyes fixed in infraduction, absent upgaze; CFEOM2: large-angle exotropia |
| Ptosis | Common, may be uni- or bilateral, progressive | Congenital, typically bilateral; chin-up head posture |
| Diplopia | Usually absent (<30%) due to gradual symmetric onset | Absent; binocular vision typically never develops |
| Pupils | Spared | Spared in CFEOM1; poorly reactive in CFEOM2 |
| Inheritance / genetics | Single large-scale mtDNA deletion (~50%, sporadic); also nuclear mtDNA-maintenance genes (POLG, RRM2B, TWNK) and mtDNA point mutations | Mendelian: CFEOM1 (AD, KIF21A); CFEOM2 (AR, PHOX2A); CFEOM3 (AD, TUBB3/TUBB2B/TUBA1A/KIF21A) |
| Systemic/associated features | “CPEO-plus”: retinopathy, ataxia, neuropathy, deafness, cardiac conduction block, diabetes (Kearns-Sayre) | Usually isolated; CFEOM3 may have developmental/CNS anomalies (e.g., Tukel syndrome) |
| Muscle biopsy | Ragged-red / COX-negative fibers; mitochondrial abnormalities | Not a mitochondrial biopsy diagnosis; muscle shows fibrosis/denervation changes |
| Orbital MRI | Mild EOM atrophy with fatty/spongiform T1 signal | EOM hypoplasia + hypoplastic ocular motor nerves |