The study stopped early, before enrolling its first participant

The purpose of the study is to prospectively and systematically collect standardized clinical information, to describe important features of the disease course of SURF1 deficiency. These include but are not limited to symptomatology, clinical course, and risk factors for severe disease and complications.

Participant eligibility for the study will be determined during a screening period lasting up to 45 days. In-clinic follow visits will occur over several days every 6 months for 2 years from baseline. Thereafter, annual telephone follow-up contact will be conducted for 2 additional years. Thus, the active study duration for each participant will be up to approximately 2 years and the total duration per participant will be approximately 4 years.

The study will be conducted in the United States and select sites outside the United States based on incidence data.

Inclusion Criteria:

• Informed consent/assent provided by the participant based on participant's cognitive ability as determined by Principal Investigator (PI), and/or participant's parent(s) or legally authorized representative(s).
• Participant is < 18 years of age at time of initial informed consent.
• Displays one or more clinical features consistent with SURF1 deficiency, including but not limited to, hypotonia, motor delays, motor regression, failure to thrive, language delays, and/or language regression.
• Genetic diagnosis of SURF1 pathogenic or likely pathogenic mutation(s), either compound heterozygous or homozygous mutations. If variants are of uncertain significance (VUS), verify documentation of cytochrome c oxidase (COX) activity deficiency.
• Ability to travel to the study site and adhere to study-related follow-up examinations and/or procedures and provide access to participant's medical records.

Exclusion Criteria:

• Any known genetic abnormality (other than SURF1 deficiency), including but not limited to a chromosomal aberration or molecularly known or clinically suspected progressive neurometabolic disorder or dementia, that confounds the clinical phenotype.
• The presence of significant non-SURF1-related central nervous system (CNS) impairment/behavioral disturbances that would confound the scientific rigor or interpretation of results of the study or a known history of perinatal asphyxia, kernicterus, carbon monoxide or methanol intoxication.
• Current participation in a therapeutic study or participation in a therapeutic study within 30 days prior to enrollment in the present study.
• Prior or current treatment with gene or stem cell therapy.
• Any condition that, in the opinion of the Site Investigator, could put the participant at undue risk and/or would ultimately prevent the completion of study procedures.

Participants with SURF1 deficiency