This is a prospective study, that will follow participants over their course of treatment on Isotretinoin. All patients who are prescribed Isotretinoin for their acne treatment are registered in iPLEDGE. The iPLEDGE program involves a set of steps that the patient, physician and pharmacist must follow for the patient to take Isotretinoin. Patients will be asked if they are willing to participate in this research study to determine musculoskeletal changes in adolescents and young adults on systemic therapy using the highly sensitive magnetic resonance (MR) imaging modality. In addition to the MRI, participants will be asked if they are willing to give an extra sample of blood when their routine blood work is being done for iPLEDGE. This blood sample will be used to determine if there are any effects of isotretinoin on bone turnover markers.