Table 1. Clinical, histochemical and molecular details of the novel mt-tRNA^Ala mutations and previously-reported mt-tRNA^Ala mutations.

Mutation (patient)	Age of onset (gender)	Phenotype	Histological findings	Level of heteroplasmy in muscle	Threshold single fibre level	CK (normal: <2.4 μmol/l)
m.5631G>A (Patient 1)	29 (f)	Distal and proximal paresis. Mild symmetrical ptosis, but no external ophthalmoplegia	Numerous COX-deficient fibres (33%) in addition to ragged-red-fibres (2 %)	92%	approx. 96%	up to 3.9 μmol/l
m.5610G>A (Patient 2)	69 (f)	Proximal Paresis. No ptosis and no external ophthalmoplegia	Mild myopathic changes. Numerous COX-deficient fibres (40%) in addition to ragged-red-fibres (5%)	91%	approx. 97%	up to 2.7 μmol/l
m.5591G>A 14	45 (m)	Proximal paresis of arms and legs and distal paresis of both arms. No ptosis and no external ophthalmoplegia	Mild myopathic changes. Marked number (~80%) of COX-deficient fibres with ragged-red fibres (30%)	98%	approx. 98%	up to 12.31 μmol/l
m.5591G>A 14 *	51 (m)	Proximal paresis. No ptosis and no external ophthalmoplegia	Numerous number of COX-deficient fibres (60%). Small number of ragged-red fibres	not determined in muscle; urine: 67%	Not determined	up to 7.07 μmol/l
m.5650G>A 15	6 (f)	Proximal paresis. Mild bilateral ptosis, but no external ophthalmoplegia	Marked number of COX-deficient fibres (>50%), marked variation in fibre size, evidence of inflammatory changes	>95%	approx. 99%	up to 6.25 μmol/l
m. 5628T>C 16	77 (f)	Proximal paresis, episodic diplopia, external ophthalmoplegia and dysphagia. No ptosis	Many COX-deficient fibres (30%) and ragged-red fibres	40%	Not determined	normal
m.5636T>C 17	7 (m)	Fatigue syndrome, bilateral ptosis, external ophthalmoplegia, mild dysarthria. No paresis.	Signs of chronic myopathy. Several COX-deficient fibres and ragged-red fibres	31%	>80%	up to 8.95 μmol/l

^*Brother of the patient above who initially presented with asymptomatic elevation of CK levels