Reference [5] | Reference [6] | Reference [7] | Our case | |
---|---|---|---|---|
Number of the patients | 2 | 4 | 9 | 1 |
Ethnicity | English | Two Indian; one Greek Pomak; one Pakistani | Arabian | Chinese |
Variants | R247Q | R247Q | R247Q in 6 pts.; D69Y in 3 pts | R210X; V49M |
Zygosity | Homozygous | Homozygous | Homozygous | Compound heterozygous |
Age at onset | Less than 2 years | Infancy | Infancy | 9 months |
CMS-associated features | ||||
Fatigability | Yes | Yes | Yes | Yes |
Ocular involvement | Ptosis and/or diplopia | Ptosis and/or diplopia | Ptosis and/or diplopia | Ptosis and ophthalmoplegia |
Cervical muscle weakness | Neck flexion weakness in one patient | Neck flexion weakness in one patient | No | No |
Bulbar weakness | Dysarthria with fatigable speech in one patient | In 2 pts | Stridor in 2 pts.; No stridor in 5 pts.; ND in 2 pts | Yes, stridor and dysarthria |
Limb muscle weakness | Yes, proximal | Yes, proximal | Yes, proximal | Yes, proximal |
Facial involvement | In one patient | ND | ND | Yes, chewing weakness |
Myasthenic crises | No | No | No | Yes, twice |
RNS on 3 Hz stimulation | Negative in one patient; ND in one patient | Positive in 2 pts.; Negative in 2 pts | Positive in one patient; Negative in 5 pts.; ND in 3 pts | Positive |
Abnormal jitter with block | Positive in one patient; ND in one patient | Negative in one patient; ND in 3 pts | ND | ND |
Other features | ||||
Hypotonia | No | Hypermobility in two pts | No | Yes |
Epilepsy | No | No | No | Yes |
Intellectual disability | Mild | Mild | Mild ID in 2 pts.; No ID in 3 pts.; ND in 2 pts.; NA in 2 pts | Mild |
Urinary organic acids | Normal | Normal in one patient; ND in 3 pts | Normal in 2 pts.; ND in 7 pts | Mild elevation of 2-oxoglutaric acid and lactate |
Blood lactate levels | Normal | Elevation after exercise in 2 pts | Normal | Mild elevation |
Muscle biopsy | Enlarged mitochondria and increased in number on EM in one patient; ND in one patient | Fibre size variation, few central cores and sporadically accumulated mitochondria on EM in one patient; Mildly atrophic fibre, normal COX staining and mild reduction in complex 1 activity in one patient; ND in two pts. | Normal in one patient; Non-specific results in one patient; ND in 7 pts | Atrophy of type IIB muscle fibre with normal COX and SDH staining; No changes in mitochondria on EM |
Responsive to treatment | ||||
AChEI | Partial response in one patient; No response in one patient | Partial response in one patient; No response in 3 pts | No response in 2 pts.; ND in 7 pts | Yes, Partial |
3,4-DAP | Good response in one patient; ND in one patient | ND | ND | ND |
Salbutamol | ND | No response in 2 pts.; ND in 2 pts | ND | No |