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Start free with EleplanTK2-related mitochondrial DNA maintenance defect, myopathic form
ORPHA:254875Disease
Also called TK2 deficiency · Thymidine kinase 2 deficiency · TK2d
What it is
A rare mitochondrial DNA depletion syndrome characterized by muscle weakness, and progressive, generalized hypotonia due to depletion of mtDNA in skeletal muscles. Clinical progression ranges from rapid and early fatal course due to respiratory failure, to slowly progressive myopathy over the course of childhood or even early adulthood.
Key facts
- Prevalence
- <1 / 1 000 000
- Age of onset
- Infancy, Neonatal
- Inheritance
- Autosomal recessive
- Classified as
- Disease
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Common30–79%
20- Chronic fatigue
- Developmental regression
- Difficulty standing
- Distal muscle weakness
- Exercise intolerance
- Failure to thrive in infancy
- Feeding difficulties in infancy
- Gait disturbance
- Generalized muscle weakness
- Generalized-onset seizure
- Hyporeflexia
- Hypotonia
- Infantile encephalopathy
- Motor delay
- Progressive proximal muscle weakness
- Recurrent pneumonia
- Respiratory distress
- Respiratory failure
- Respiratory insufficiency due to muscle weakness
- Skeletal muscle atrophy
Sometimes5–29%
12- Bilateral ptosis
- Bulbar palsy
- Cognitive impairment
- Dysarthria
- Dysphagia
- Infantile sensorineural hearing impairment
- Myalgia
- Ophthalmoparesis
and 4 more in this range
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes reported in subtypes
Orphanet records this gene on 3 more specific entries under this disorder, not on this entry itself:
A well-studied disease is usually split into subtypes, and the gene is curated on whichever one the evidence belongs to. Open a subtype to see which gene goes with it.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Benefit programs to look at
Programs whose eligibility touches the same ICD-10 categories. Eligibility is decided by the administering agency, never by this page.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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