Char Witmer, MD, MSCE

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Char Witmer, MD, MSCE, is the Clinical Director of Hematology and the Assistant Director of the Hemostasis and Thrombosis Center at Children’s Hospital of Philadelphia.

Areas of Expertise: Bleeding and clotting disorders, Sickle cell disease, General hematology

Appointments and Referrals: 1-800-TRY-CHOP (1-800-879-2467)

Education and Training

Medical School

MD - University of Rochester School of Medicine and Dentistry, Rochester, NY


Pediatrics - Children's Hospital of Philadelphia, Philadelphia, PA


Hematology/Oncology - Children's Hospital of Philadelphia, Philadelphia, PA

Board Certification

Pediatric Hematology-Oncology – American Board of Pediatrics
Pediatrics – American Board of Pediatrics

Graduate Degree

MS in Clinical Epidemiology - University of Pennsylvania Center for Clinical Epidemiology and Biostatistics, Philadelphia, PA

Titles and Academic Titles

Clinical Director, Hematology

Assistant Director, Hemostasis and Thrombosis Center

Medical Director, 5WA Hematology Inpatient Unit

Attending Physician

Clinical Associate Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania

Conditions Treated

Departments and Services




Clark HH, Ballester L, Whitworth HB, Raffini L, Witmer C: Prevention of Recurrent Thrombotic Events in Children with Central Venous Catheter-Associated Venous Thrombosis. Blood 139: 452-460, Jan 2022.

O'Brien SH, Stanek JR, Witmer CM, Raffini L: The Continued Rise of Venous Thromboembolism Across U.S. Children's Hospitals. Pediatrics March 2022.

Adang LA, Gavazzi F, D'Aiello R, Isaacs D, Bronner N, Arici ZS, Flores Z, Jan A, Scher C, Sherbini O, Behrens EM, Goldbach-Mansky R, Olson TS, Lambert MP, Sullivan KE, Teachey DT, Witmer C, Vanderver A, Shults J: Hematologic abnormalities in Aicardi Goutières Syndrome. Mol Genet Metab June 2022.


Le Gal G, Carrier M, Castellucci L, Cuker A, Hansen JB, Klok FA, Langlois NJ, Levy JH, Middledorp S, Righini M, Walters S, ISTH CDE Task Force: Development and implementation of common data elements for venous thromboembolism research: on behalf of SSC Subcommittee on official Communication from the SSC of the ISTH. J Thromb Haemost 19: 297-303, Jan 2021 Notes: On the ISTH CDE Task Force (name noted in manuscript).

Blatz AM, Oboite M, Chiotos K, Castelo-Soccio L, Odom John AR, for the Children's Hospital of Philadelphia MIS-C Research Collaborative: Cutaneous Findings in SARS-CoV-2-Associated Multisystem Inflammatory Disease in Children. Open Forum Infect Dis 16, Feb 2021 Notes: Member of the Children's Hospital of Philadelphia MIS-C Research Collaborative, name included in manuscript.

Doshi B, Witmer C: Recurrence of a high titer factor VIII inhibitor in a hemophilia A patient on emicizumab prophylaxis. Haemophilia July 2021.

Breton J, Witmer CM, Zhang Y, Downing M, Stevenson J, McDermott J, Siddique SM, Grossman AB: Utilization of an Electronic Medical Record-integrated Dashboard Improves Identification and Treatment of Anemia and Iron Deficiency in Pediatric Inflammatory Bowel Disease. Inflamm Bowel Dis August 2021.


Jaffray J, Witmer C, O'Brien SH, Diaz R, Ji L, Krava E, Young G: Peripherally Inserted Central Catheters Lead to a High Risk of Venous Thromboembolism in Children. Blood 135: 220-226, Jan 2020.

Malec LM, Cheng D, Witmer CM, Jaffray J, Kouides PA, Haley KM, Sidonio RF, Johnson K, Recht M, White G, Croteau S, Ragni M: The impact of extended half-life factor concentrates on prophylaxis for severe hemophilia in the United States. Am J Hematol 95, Aug 2020.

Thom CS, Echevarria E, Osborne AD, Carr L, Rubey KM, Salazar E, Callaway d, Pawlowski T, Devine M, Kleinman S, Witmer C, Flibotte J, Lambert MP: Extreme thrombocytosis is associated with critical illness and young age, but not increased thrombotic risk, in hospitalized pediatric patients. Journal of Thrombosis and Haemostasis September 2020 Notes: Online ahead of print. PMCID: 32979018

Diorio C, McNerney KO, Lambert M, Paessler M, Anderson AE, Henrickson SE, Chase J, Liebling E, Burudpakdee C, Lee J, Balamuth F, Blatz AM, Chiotis K, Fitzgerald JC, Giglia T, Gollomp K, Odom-John AR, Jasen C, Leng T, Petrosa W, Vella LA, Witmer C, Sullivan KE, Laskin B, Hensley SE, Bassiri H, Behrens EW, Teachey DT: Evidence of Thrombotic Microangiopathy in Children with SARS-CoV-2 Across the Spectrum of Clinical Presentations. Blood Advances 4: 6051-6063, Dec 2020.


Amos LE, Silvey M, Hall M, Witmer CM, Carpenter SL: Primary Thromboprophylaxis in Hospitalized Children: A Multi-Center Retrospective Analysis. Thrombosis Research 176: 1-7, Feb 2019 Notes: Epub ahead of print.

Doshi BS, Rogers RS, Whitworth HB, Stabnick EA, Britton J, Butler RB, Obstfeld AE, Witmer CM: Utility of repeat testing in the evaluation for von Willebrand disease in pediatric patients. J Thromb Haemost 11: 1838-47, Nov 2019.


McDonnell A, Bride KL, Lim D, Paessler M, Witmer CM, Lambert MP: Utility of the Immature Platelet Fraction in Pediatric Immune Thrombocytopenia: Differentiating from Bone Marrow Failure and Predicting Bleeding Risk. Pediatr Blood Cancer 65(2), Feb 2018 Notes: Epub ahead of print.


Galvez JA, Pappas JM, Ahumada L, Martin JN, Simpao AF, Rehman MA, Witmer C: The use of natural language processing on pediatric diagnostic radiology reports in the electronic health record to identify deep venous thrombosis in children. J Thromb Thrombolysis Aug 2017 Notes: Epub ahead of print.

Witmer CM, Sauck E, Raffini LJ: A Survey of Pediatric Hematologist/Oncologist Regarding the Management of Central Line Associated Venous Thrombosis. Pediatric Blood & Cancer 64, Jul 2017.

Lambert MP, Witmer CM, Kwiatkowski JL: Therapy Induced Iron Deficiency in Children Treated with Eltrombopag for Immune Thrombocytopenia. American Journal of Hematology 92: E88-E91, Jun 2017.


Wong, TE, Nguyen, T, Shah, SS, Brogan, TV, Witmer, CM: Antithrombin concentrate use in pediatric extracorporeal membrane oxygenation (ECMO): a multi-center cohort study. Pediatr Crit Care Med 17: 1170-1178, Dec 2016. PMCID:  27662567

Sood S, James A; Ragni MV, Shapiro A,  Witmer, C, Vega R, Bolgiano D, Konkle B: A Prospective Study of von Willebrand Factor Levels and Bleeding in Pregnant Women with Type 1 von Willebrand Disease. Haemophilia 22: e562-e564, Nov 2016. PMCID: 26206486

Witmer, CM, Lambert, MP, O'Brien, SH, Neunert, C: Multicenter Cohort Study Comparing U.S. Management of Inpatient Pediatric Immune Thrombocytopenia to Current Treatment Guidelines. Pediatr Blood Cancer 63(7): 1227-31, Jul 2016. PMCID: 26929009

Malec LM, Moore CG, Bujnicki HL, Yee DL, Kerlin BA, Witmer CM, Kulkarni R, Gupta S, Gunawardena, S, Kouides PA, Brown D, Bennett CM, Ragni MV: Validation Study of the Composite Score To Identify Von Willebrand Disease in Children. Journal of Pediatric Hematology Oncology 38(2): 139-42, Mar 2016. PMCID: 26535774


Blevins, EM, Glanz, K, Huang, YV, Raffini, L, Shinohara, RT, Witmer, C: A Multicenter Cohort Study of Inferior Vena Cava Filter Use in Children. Pediatric Blood and Cancer 62(12): 2089-2093, Dec 2015.

Antun A, Monahan P, Manco-Johnson M, Callahan M, Young G, Kanin M, Knoll C, Carpenter S, Davis JA, Guerrera M, Kruse-Jarres R, Ragni M, Witmer C, McCracken CE, Kempton CL: Inhibitor Recurrence after Immune Tolerance Induction: a Multicenter Retrospective Cohort Study. J Thromb Haemost 13: 1980-8, Nov 2015. PMCID: 26382916

Witmer, CM: Low Mortality from Intracranial Hemorrhage in Pediatric Patients with Hemophilia.  Haemophilia 21(5): e359-e363, Sept 2015.

McGee, S, Raffini, L, Witmer, C: Organized sports participation and the association with injury in pediatric patients with haemophilia. Haemophilia 21(4): 538-542, July 2015.


Lin K, Kerur B, Witmer C, Beslow L, Licht DJ, Ichord RN, Kaufman BD: Thrombotic Events in Critically Ill Children with Myocarditis. Cardiology in the Young 24(5): 840-7, Oct 2014.

Bruno C, Beslow L, Witmer C, Vossough A, Jordan LC, Zelonis S, Licht DJ, Ichord RN, Smith SE: Hemorrhagic Stroke in Term and Late Preterm Neonates. Archives of Disease in Childhood Fetal and Neonatal Edition 99(1): F48-F53, Jan 2014. PMCID: 23995383


Wong TE, Huang YS, Weiser J, Brogan TV, Shah SS, Witmer CM: Antithrombin Concentrate Use in Children: A Multicenter Cohort Study. The Journal of Pediatrics 163(5): 1329-1334, Nov 2013.


Elden L, Reinders M, Witmer C: Predictors of bleeding disorders in children with epistaxis: value of preoperative tests and clinical screening. International Journal of Pediatric Otorhinolaryngology 76(6): 767-71, Jun 2012.

Puetz J, Witmer C, Huang YS, Raffini L: Widespread use of fresh frozen plasma in US children's hospitals despite limited evidence demonstrating a beneficial effect. The Journal of Pediatrics 160(2): 210-215, Feb 2012.


Witmer CM, Huang YS, Lynch K, Raffini LJ, Shah SS: Off-label recombinant factor VIIa use and thrombosis in children: a multi-center cohort study. The Journal of Pediatrics 158(5): 820-825.e1, May 2011. PMCID: PMC3075379

Witmer C, Presley R, Kulkarni R, Soucie JM, Manno CS, Raffini L: Associations between intracranial haemorrhage and prescribed prophylaxis in a large cohort of haemophilia patients in the United States. British Journal of Haematology 152(2): 211-6, Jan 2011.


Raffini L, Huang YS, Witmer C, Feudtner C: Dramatic increase in venous thromboembolism in children's hospitals in the United States from 2001 to 2007. Pediatrics 124(4): 1001-8, Oct 2009.

Witmer CM, Manno CS, Butler RB, Raffini LJ: The clinical management of hemophilia and head trauma: a survey of current clinical practice among pediatric hematology/oncology physicians. Pediatric Blood & Cancer 53(3): 406-10, Sep 2009.

Witmer CM, Elden L, Butler RB, Manno CS, Raffini LJ: Incidence of bleeding complications in pediatric patients with type 1 von Willebrand disease undergoing adenotonsillar procedures. The Journal of Pediatrics 155(1): 68-72, Jul 2009.


Witmer CM, Raffini LJ, Manno CS: Utility of computed tomography of the head following head trauma in boys with haemophilia. Haemophilia  13(5): 560-6, Sep 2007.

Witmer CM, Steenhoff AP, Shah SS, Raffini LJ: Mycoplasma pneumoniae, splenic infarct, and transient antiphospholipid antibodies: a new association? Pediatrics 119(1): e292-5, Jan 2007.




Giglia TM, Kim Y, Witmer C: Anticoagulation and Thrombosis in Adults with CongenitalHeart Disease. Cardiac Intensive Care of the Adult with Congenital Heart Disease. 1st Edition. da Cruz E,Macrae D, Webb G (eds.). Springer-Verlag London, Ltd, London, 2018 Notes: In press.


Jaffray J, Witmer C: Pediatric Venous Thromboembolism  Patient Safety and Quality in Pediatric Hematology/Oncology and Stem Cell Transplantation.  Dandoy CE, Hilden J, Billett AL, Mueller BU (eds.). Springer, 1: 377, 2017.


Giglia, T, Witmer, C: Hematologic Aspects of Pediatric and Adolescent Heart Disease: Bleeding, Clotting and Blood Component Abnormalities. Moss and Adams' Heart Disease In Infants, Children and Adolescents: Including the Fetus and Young Adult. 9th edition. Allen HD, Shaddy RE, Penny DJ, Feltes TF and Cetta F (eds.). Wolters Kluwer, 2016 Notes: Also an author for the 8th Edition.

Blevins E, Witmer C: Hematology  Philadelphia Guide to Inpatient Pediatrics. Shah SS, Zaoutis LB, Catallozzi MC, Frank G (eds.). McGraw Hill Education, Page: 169-188, 2016 Notes: Also participated in the 1st edition release in 2005.


Witmer CM: Bleeding, Disseminated Intravascular Coagulation, Hemophilia, Thrombosis, and von Willebrand Disease. The 5-Minute Pediatric Consult, 7th ed. Cabana MD, Brakeman P, Curran ML, DiMeglio LA, Golden WC, Goldsby RE, Hartman AL, Kind T, Lee CKK, Lightdale JR, Sabella C, Tanel RE (eds.). Wolters Kluwer  Page: 8-9, 304-305, 428-429, 920-921, 992-993, 2015 Notes: Also authored in the 4th, 5th and 6th editions.


Bickert Poon B, Witmer CM and Pruemer J: Coagulation Disorders. Pharmacotherapy: A Pathophysiologic Approach, 9th ed.  DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM  (eds.). McGraw-Hill Education, Page: 1625-1642, 2014 Notes: Also an author in the 7th and 8th Editions.


Witmer C, Gallagher S, Wong C, Litman R: Hematologic Diseases. Basics of Pediatric Anesthesia. Ronald S. Litman (eds.). Ronald S. Litman, Page: 69-76, 2013.

Posters and Presentations


Shaeffer G, Hlela H, Witmer C, Karavite D, Muthu N, Shelov E: A Computational Ethnographic Approach to Evaluating Alert Acceptance. Poster presentation at the Human Factors and Ergonomics Society Healthcare Symposium in Toronoto, CA March 2020.

Invited Lectures


Witmer C. "VTE Prevention in Hospitalized Pediatric Patients." American Society Pediatric Hematology Oncology Annual Meeting. Pittsburgh, PA. May 2022.


Witmer C. "Thrombosis in Children With SARS-CoV2 Related Illness." Stony Brook Pediatric Grand Rounds, virtual. Nov 2021.

Witmer C. "Prevention of Venous Thromboembolism in Hospitalized Pediatric Patients." Mid-Atlantic/Region III Federally-Funded Hemophilia Treatment Centers 2021 Annual Meeting, virtual. Apr 2021.

Witmer C. "Anticoagulation and Pediatric CSVT." American Society of Hematology Annual Meeting, virtual. Apr 2021.

Witmer C. "Sports Participation in the Student Athlete at Risk for Bleeding." University of Rochester Golisano Children's Hospital Pediatric Resident Noon Conference, virtual. Feb 2021.

Witmer C."Thrombosis in Children with SARS-CoV2 Related Illness." University of Rochester Golisano Children's Hospital Pediatric Grand Rounds Twig Lectureship, virtual. Feb 2021.


Witmer C. "Anticoagulation in Children with SARS-CoV-2 Related Illness." POPCoRNetwork (Pediatric Overflow Planning Contingency Response Network), virtual presentation. Oct 2020.

Witmer C. "Use of Prothrombin Complex Concentrates in Pediatrics." Congress of the Mexican Society of Hemostasis and Thrombosis (SOMETH), virtual conference. Sept 2020.

Witmer C. "Hemostatic Disorders in Children with COVID-19." Congress of the Mexican Society of Hemostasis and Thrombosis (SOMETH), virtual conference. Spet 2020.

Witmer C. "Thrombolysis in the Pediatric Patient." Congress of the Mexican Society of Hemostasis and Thrombosis (SOMETH), virtual conference. Sept 2020.


Witmer C. "Pediatric Central Venous Catheter Related Thrombosis." International Society on Thrombosis and Haemostasis (ISTH), International Webinar. Nov 2019.

Awards and Honors

2017, Alan R. Cohen Master Clinician Award, Children's Hospital of Philadelphia
2017, Distinguished Teaching Award for Hematology, Children's Hospital of Philadelphia
2017, 2019, Faculty Teaching Honor Roll, Children's Hospital of Philadelphia
2003, Senior Resident Humanitarian Award, The Children's Hospital of Philadelphia
2000, The Janet M. Glasgow Memorial Achievement Citation - American Medical Women's Association
2000, Alpha Omega Alpha, University of Rochester School of Medicine
1996, Phi Beta Kappa, University of Rochester

Editorial and Academic Positions

Editorial Positions

2013-present, Review Editorial Board Member, Frontiers in Obstetric and Pediatric Pharmacology
2007-present, Editorial Advisory Board Member, National Hemophilia Foundation publication HemAware

Ad Hoc Reviewer

2017-present, Research and Practice in Thrombosis and Haemostasis
2016-present, Therapeutic Advances in Drug Safety
2015-present, Pediatric Blood and Cancer
2014-present, British Journal of Haematology
2013-present, Archives of Pathology
2012-present, European Journal of Pediatrics
2012-present, Thrombosis and Haemostasis
2008-present, Journal of Pediatric Hematology/Oncology
2008-present, Pediatric Emergency Care
2008-present, Journal of Pediatrics
2008-present, Blood
2008-present, Thrombosis Research
2008-present, Pediatrics
2008-present, Haemophilia

Academic and Institutional Committees

2021-present, Clinical Affairs Committee, CHOP
2019-present, Hematology Oncology Fellow Clinical Competency Committee, CHOP
2019-present, Vascular Access Steering Committee
2019-present, Laboratory Stewardship Program Committee
2016-present, Pediatric Hematology Oncology Fellowship Committee, CHOP
2014-present, Venous Thromboembolism (VTE) Steering Committee, CHOP
2013-present, Perelman School of Medicine Medical Student Clinical Research Paper Prize Committee
2013-present, EPIC SUGr (Super Users Group) Initiative, CHOP
2011-present, Alumni Committee, CHOP

Leadership and Memberships

Memberships in Professional Organizations


2005-present, International Society on Thrombosis and Haemostasis


2018-present, American Thrombosis and Hemostasis Network
 - 2018-present, Community Counts Publication Committee
2016-present, American Board of Pediatrics
 - 2016-present, Subboard of Pediatric Hematology-Oncology
2012-present, Centers for Disease Control and Prevention
 - 2012-present, Presentation and Publication Committee
 - 2012-present, Blood Disorders Universal Data Collection Project, Committee Member
2005-present, The American Society of Pediatric Hematology/Oncology
 - 2016-present, Nominating Committee
2005-present, Hemostasis and Thrombosis Research Society
2004-present, American Society of Hematology