Table 2. [Clinical Manifestations of TK2-Related Mitochondrial DNA Maintenance Defect]. - GeneReviews®

Age of Onset	Prevalence	Manifestation	Frequency
Age <2 years (infantile onset)	61/89 (69%)	Hypotonia	55/57 (96%)
Elevated serum CK	56/59 (95%)
Respiratory difficulties	48/53 (91%)
Loss of previously acquired motor skills	43/49 (88%)
mtDNA depletion	33/40 (83%)
Hyporeflexia	31/39 (79%)
Lactic acidemia	28/42 (67%)
Motor developmental delay	18/49 (37%)
Seizures	11/34 (32%)
Cognitive impairment	4/43 (9%)
Age 2-18 years (juvenile/ childhood onset)	14/89 (16%)	Muscle weakness	8/9 (89%)
mtDNA depletion	9/14 (64%)
Respiratory failure	7/12 (58%)
Age >18 years (adult onset)	14/89 (16%)	Dysphagia	5/5 (100%)
mtDNA multiple deletions	4/4 (100%)
Muscle weakness	8/8 (100%)
Ptosis	7/7 (100%)
Ragged red fibers	8/8 (100%)

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