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Samuel Andrew Merrill, M.D., Ph.D.

Photo of Dr. Samuel Andrew Merrill, M.D., Ph.D.

Instructor of Medicine

Specializes in: Adults (18+ years)

Expertise: Anemias, Atypical Hemolytic Uremic Syndrome (aHUS), Thrombocytopenias

Research Interests: AIHA, HLH, hyperhemolysis, aHUS, complement


Dr. Merrill is a clinician scientist with laboratory investigations into mechanisms of severe anemias from altered erythrocyte survival. His research focuses on complement-mediated erythrocyte destruction, including atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, autoimmune hemolytic anemia, and hyperhemolysis syndrome. He has a clinical interest in hemophagocytic lymphohistiocytosis (HLH), where his research focus is developing processes for timely diagnosis, quality improvement, and exploring novel therapies.

Dr. Merrill completed his MD/PhD training at Washington University in St. Louis, where his research focused on cellular pathways of vesicular transport involving the ESCRT pathway. He completed his Internal Medicine residency and Chief residency at the University of Vermont, and his Hematology fellowship and Chief fellowship at Johns Hopkins. more


  • Instructor of Medicine

Departments / Divisions



  • MD PhD, Washington University School of Medicine in St Louis (2011)


  • University of Vermont College of Medicine / Internal Medicine (2015)


  • Johns Hopkins University School of Medicine / Hematology and Oncology (2018)

Additional Training

  • Internal Medicine, American Board of Internal Medicine (2014)
  • Hematology, American Board of Internal Medicine (2017)

Research & Publications

Research Summary

I am a clinician scientist with laboratory investigations into mechanisms of severe anemias from altered erythrocyte survival.

I am using our understanding of hemolytic anemias driven by complement (PNH, aHUS) to help determine how hyperhemolysis occurs, and the alterations of the erythrocyte surface that predispose to complement activation.

Our goal is to use this mechanistic understanding to develop precision medical therapies for sickle cell disease to improve anemia, and specifically to treat hyperhemolysis. These findings may be further applied to hemolytic anemias as a class.

Selected Publications

View all on Pubmed

Vaught AJ, Braunstein EM, Jasem J, Yuan X, Makhlin I, Eloundou S, Baines AC, Merrill SA, Chaturvedi S, Blakemore K, Sperati CJ, Brodsky RA. Germline mutations in the alternative pathway of complement predispose to HELLP syndrome. JCI Insight. 2018;3(6)

Merrill SA, Naik R, Braunstein E, Streiff M, Shanbhag S, Lanzkron S, Moliterno A, Brodsky RA. (2017). Adult Hemophagocytic Lymphohistiocytosis—A Quality Improvement Initiative. Blood, 130(Suppl 1) 677-677

Merrill SA, Brittingham ZD, Yuan X, Moliterno AR, Sperati CJ, Brodsky RA. (2017). Eculizumab cessation in atypical hemolytic uremic syndrome. Blood, 130(3) 368-372

Merrill SA and Hanson PI. (2010). Activation of Human VPS4A by ESCRT-III Proteins reveals ability of Substrates to relieve Enzyme Autoinhibition. Journal of Biological Chemistry 285 (46): 35428-3

Shim S, Merrill SA, Hanson PI. (2008). Novel Interactions of ESCRT-III with LIP5 and VPS4 and their Implications for ESCRT-III disassembly. Molecular Biology of the Cell 19(6): 2661-2672

Contact for Research Inquiries

Hematology Office
720 Rutland Ave
Ross Bldg, Room 1025
Baltimore, MD 21205 map

Activities & Honors


  • Galileo Circle Scholar, University of Arizona, 2003
  • Award for Excellence in the Biological Sciences, College of Science, University of Arizona, 2004
  • Academic Award of Excellence, Honors College, University of Arizona, 2004
  • Distinguished Young Scholar Award, Washington University in St Louis School of Medicine, 2004
  • Harriet P Dustan, M.D. Research Award, The University of Vermont, 2014
  • Abstract Achievement Award, American Society of Hematology, 2014
  • Young Achiever Award, American College of Physicians, 2014
  • Abstract Achievement Award, American Society of Hematology, 2017
  • Levin-Conley Fellowship, Johns Hopkins University School of Medicine, 2018


  • American Society of Hematology

Professional Activities

  • Attending Physician, Johns Hopkins Hematology

Patient Ratings & Comments

The Patient Rating score is an average of all responses to physician related questions on the national CG-CAHPS Medical Practice patient experience survey through Press Ganey. Responses are measured on a scale of 1 to 5, with 5 being the best score. Comments are also gathered from our CG-CAHPS Medical Practice Survey through Press Ganey and displayed in their entirety. Patients are de-identified for confidentiality and patient privacy.

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