A RETROspective Study of Patients With TK2d

Study Overview
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Brief Summary
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This is a medical chart review study to collect information for patients who have been taking pyrimidine nucleosides for treatment of TK2 deficiency. Information from the time of onset of symptoms will be collected to describe the pre treatment course of TK2 deficiency.

Detailed Description
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Data to be collected from the time of onset of symptoms related to TK2 deficiency includes medical conditions and/or adverse events (AEs); these should include relationship to TK2 disease and/or pyrimidine nucleosides, as appropriate, as well as date of onset and severity, when available. When available, test reports may be obtained as well as available research biological samples (eg, blood or tissue samples that may be tested for biomarkers of disease and/or effects of medications to treat the mitochondrial disease).

Official Title
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A RETROspective Study of the Combination of Pyrimidine Nucleos(t)Ides in Patients With Thymidine Kinase 2 Deficiency (TK2)

Conditions
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Thymidine Kinase 2 (TK2)

Intervention / Treatment
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* Drug: dC/dT


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Signed informed consent by the patient or parent(s)/legally authorized representative (LAR) and/or assent by the patient (when applicable), unless the associated institutional review board (IRB) or ethics committee (EC) provides an appropriate consent waiver Confirmed genetic mutation in the TK2 gene Availability of medical records for each patient from the time of onset of symptoms Patient has taken pyrimidine nucleos(t)ides (dCMP/dTMP and/or dC/dT) as substrate enhancement therapy for TK2 deficiency Most recent patient visit at which efficacy and/or safety parameters were collected occurred between 01 June 2018 and 15 December 2018 Exclusion Criteria: 1. Presence of other genetic disease or polygenic disease
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Drug: dC/dT|Collection of retrospective data from TK2 patients previously treated with dC/dT|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diagnosis | genetic testing (previously conducted) | 3 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinical course | BMI (height in inches and weight in kg will be combined to report BMI in kg/m^2) | 3 months | 
| Clinical course | achievement, loss, or regaining of developmental motor milestones | 3 months | 
| Motor function and ambulatory assessments | Change in 6-minute walk test [6MWT] distance (in meters) | 3 months | 
| Motor function and ambulatory assessments | Motor Function Measure [MFM] 20 or MFM 32 | 3 months | 
| Motor function and ambulatory assessments | Egen Klassifikation | 3 months | 
| Motor function and ambulatory assessments | North Star Ambulatory Assessment | 3 months | 
| Motor function and ambulatory assessments | Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders [CHOP INTEND] | 3 months | 
| Motor function and ambulatory assessments | Hammersmith Functional Motor Scale-Expanded [HFMSE] | 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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myopathy, muscle weakness, hypotonia, dysphagia, ptosis