1. Patient is between the ages of 29 days - 6 years old
2. Confirmed ACTA2 pathogenic variant
3. Available medical records since birth that permit documentation of disease characteristics and developmental milestone
4. Have two parents and/or legal guardians who are English speaking and are able to read, understand, and sign the informed consent
5. Able to tolerate travel to study site

1. Patient is between the ages of 7 - 18 years old
2. Confirmed ACTA2 pathogenic variant
3. Available medical records since birth that permit documentation of disease characteristics and developmental milestone
4. Have two parents and/or legal guardians who are English speaking and are able to read, understand, and sign the informed consent
5. Able to tolerate travel to study site

1. Patient is between the ages of 19 - 100 years old
2. Confirmed ACTA2 pathogenic variant
3. Available medical records since birth that permit documentation of disease characteristics and developmental milestone
4. Patient, parent and/or legal guardian is English speaking is able to read, understand, and sign the informed consent
5. Able to tolerate travel to study site

1. Patient of any age, alive or deceased
2. Confirmed ACTA2 pathogenic variant
3. Available medical records since birth that permit documentation of disease characteristics and developmental milestone
4. Patient, parent and/or legal guardian is English speaking and able to read, understand, and sign the informed consent

1.1 Develop patient surveys and identify retrospective/existing clinical data sources for aggregation, harmonization, and analyses of outcomes and biomarkers to be compared to existing published data. 1.2. Identify modifiers of symptom progression in patients with MSMDS. 1.3 Correlate the degree of disease progression by systems in 40 patients (cross-sectional study) and construct an MSMDS Rating Scale to evaluate disease severity and progression in children. 1.4 Create case report forms based on previously known and developed surveys in 1.1. to allow for standardized prospective data collection (Outcome 2).

2.1 Assess vascular and non-vascular disease progression over 3 years. 2.2 Compare the trajectory between clinical rating scales and patient-reported outcomes. 2.3 Correlate disease progression by individual and MSMDS-specific scale with other variables (age at diagnosis, sex, genetic variance, surgeries, etc).

Use the Actigraphy wearable technology system in conjunction with a video consult to remotely assess gait, limb movement and exercise performance.