Evaluation of Safety and Efficiency of Metreleptin Treatment for Patients With Multiple Symmetric Lipomatosis (MSL)

Inclusion Criteria: * Have the clinical diagnosis of MSL and being followed at University of Michigan (cohort to be studied in this proof-of-concept study is already available at Michigan). * Willing and able to tolerate the study procedures. * Willing and able to tolerate blood sampling. * Having no condition that may impede successful data collection or interfere with testing parameters. * \<60 years of age. * If female of childbearing potential: * Not breastfeeding. * Negative pregnancy test (human chorionic gonadotropin, beta subunit) at baseline. * Can read, understand and sign approved informed consent form, communicate with study physician, and study team, and understand and comply with protocol requirements. Exclusion Criteria: * Presence of advanced liver disease (abnormal synthetic function, prothrombin time \[PT\], or albumin) in medical records * Evidence of other etiologies of viral hepatitis in medical records * Presence of active hematologic, bone marrow or other abnormalities that may increase risk of bleeding in medical records. * Presence of HIV infection in medical records. * Presence of End-stage renal disease (ESRD), active cancer, or \>class 2 congestive heart failure based on medical history and physical examination. * Active chronic infection (e.g., known chronic osteomyelitis or Tuberculosis \[TB\]). May have transient infections but must be free of active infection for two weeks prior to study visits. * Unable to ambulate or tolerate trips to the University of Michigan Clinical Research Unit. * Clinically relevant Coronary artery disease (CAD): history of stent or Coronary artery bypass graft surgery (CABG) with cardiologist confirmed angina. * Presence of autoimmune disease. * Hypersensitivity to metreleptin. * General obesity not associated with congenital leptin deficiency. * Any other condition that, in our opinion, may impede successful data collection.