C8305T

# **General Information**

| **Position** | **8305** | **Variant** | **m.8305C\>T** | **Locus** | **MT\-TK** | **RNA** | **tRNA Lys** |
| --- | --- | --- | --- | --- | --- | --- | --- |
| **Homoplasmy** | \- | **Heteroplasmy** | \+ | **mitoTIP** | 74\.50% | **Pathogenicity** | Reported |

"Pathogenicity" status is derived from published literature or predictions from bioinformatics tools. Researchers and clinicians are cautioned that additional data and/or analysis may still be necessary to confirm the pathological significance of these variants. For more information, please see [Mitofam Info](https://mitofam.com/doc/385/).

# **Pedigree Information**

The **m.8305C\>T** variant in MT\-TK has been reported in 1 pedigree. To date, 3 carriers have been reported. Reported mutation loads ranged from 0% to 51\.5%, with a median of 2\.5% overall; affected carriers showed mutation loads from 0% to 51\.5%, with a median of 2\.5%. In one affected carrier, the mutation was undetectable in blood (0%) and urine (0%) but exceeded 20% in muscle (51\.5%). The main clinical manifestations among affected carriers included mitochondrial myopathy, bilateral eyelid ptosis, dysphagia, episodic muscle weakness, knee extensor weakness, and mild psoas.

| **No.** | **Position** | **Variant** | **Family ID** | **Nationality** | **Diseases** | **Unaffected Maternal Relatives** | **Affected Maternal Relatives** | **Publication Year** | **PMID/Ref** | **Note** |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | 8305 | m.8305C\>T | [C8305T\-F1](https://mitofam.com/doc/2192/) | Spain | Mitochondrial myopathy | 2 | 0 | 2017 | [29174468](https://pubmed.ncbi.nlm.nih.gov/29174468/) | / |

# **Carrier Information**

| **No.** | **Position** | **Variant** | **Family ID** | **Carrier ID** | **Type (Fam/De novo/Uninf)** | **Gender (F/M)** | **Proband (Y/N)** | **Affected (Y/N)** | **Die/Alive(D/A)** | **Age** | **Blood Mutant Level** | **Muscle Mutant level** | **Urine Mutant level** | **Other Mutant level** | **Clinical Features** | **Note** |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | 8305 | m.8305C\>T | C8305T\-F1 | C8305T\-F1\-II1 | De novo | F | Y | Y | A | 44 | 0 | COX\- fibers 51\.5%; COX\+ fibers 5% | 0 | / | Mitochondrial myopathy; bilateral eyelid ptosis; episodic muscle weakness; dysphagia; mild psoas/knee extensor weakness | Bulk muscle load not reported; muscle values are from microdissected COX\-negative/COX\-positive fibers. m.8305C\>T was undetectable in blood and urinary epithelial cells from Patient 1; mother and younger brother negative in available blood/urine samples. Muscle biopsy showed RRF and COX\-negative fibers; respiratory chain complex I/III/IV defects. |
| 2 | 8305 | m.8305C\>T | C8305T\-F1 | C8305T\-F1\-II2 | Fam | M | N | N | A | ND | / | / | / | / | Healthy | Son of Patient 1; no molecular testing; neurological exam normal. |
| 3 | 8305 | m.8305C\>T | C8305T\-F1 | C8305T\-F1\-II3 | Fam | M | N | N | A | ND | / | / | / | / | Healthy | Son of Patient 1; no molecular testing; neurological exam normal. |

For abbreviations and other usage instructions, please see [Mitofam Info](https://mitofam.com/doc/385/).