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About Sickkids
About SickKids

Johann Hitzler, MD

The Hospital for Sick Children
Staff Haematologoist

Research Institute
Senior Scientist
Developmental & Stem Cell Biology

University of Toronto
Department of Paediatrics, Faculty of Medicine

Other Positions

The Hospital for Sick Children
Div. of Haematology/Oncology, Section Leukemia Lymphoma

The Hospital for Sick Children
SickKids Leukemia Research Group

The Hospital for Sick Children
Resource Allocation Committee, Haematology/Oncology

The Hospital for Sick Children
Steering Comm., Clinical Trial Support Unit, Haematology/Oncology

Phone: 416-813-7654 ext. 208887
Fax: 416-813-5327
Email: johann.hitzler@sickkids.ca

Brief Biography

Dr. Hitzler received his medical training at the University of Ulm, Germany.  He completed his paediatric residency and fellowship in the Division of Haematology/Oncology at The Hospital for Sick Children.  He obtained his post-doctoral research training at the Ontario Cancer Institute in Toronto and at St. Jude Children's Research Hospital in Memphis, TN.  He is a staff physician in the Division of Haematology/Oncology at Sickkids and a Senior Scientist in the Developmental & Stem Cell Biology Program at The Hospital for Sick Children Research Institute.  

Clinical Care Activities

The main clinical focus is the diagnosis and treatment of children with leukemia and lymphoma, particularly the leukemic disorders occurring in children with Down syndrome. 

Academic Background

Paediatric Hematology/Oncology Fellowship
The Hospital for Sick Children, 1993-06-01 - 1995-06-01

Research Interests

Acute megakaryoblastic leukemia (AMKL) is a form of acute myeloid leukemia that is defined by a platelet precursor phenotype of the leukemic blasts. Dr. Hitzler initially focused on AMKL in infants and together with colleagues at St. Jude Children's Research Hospital, discovered that the fusion of two novel genes, RBM15 and MKL1, was the molecular mechanism of the major recurrent chromosomal translocation in infants with AMKL. 

His current focus is on the megakaryoblastic and lymphoid leukemias (ALL) of children with Down Syndrome (constitutional trisomy 21). Down Syndrome is associated with a significantly increased incidence of AMKL and ALL. The Hitzler lab showed that somatic mutations of the hematopoietic transcription factors GATA1 occur both in the blasts of AMKL of Down Syndrome and those of a preceding leukemic disorder that is found in newborns with Down Syndrome, termed Transient Leukemia (TL). The Hitzler lab has established in vivo models to characterize the leukemic-initiating cells in AMKL and TL of Down Syndrome. They are interested in the events that trigger either the spontaneous long-term resolution of TL or the transformation of AMKL. The development of prognostic markers that could predict who is at high risk for this transformation is a long-term goal.  Mutational analysis of GATA1, in vivo models of TL and in vivo models of AMKL, TL and ALL in Down Syndrome are frequently used approaches in the lab. 

Dr. Hitzler is involved in the design and conduct of clinical trials for the treatment of leukemia in Down Syndrome as well as the study of late effects of leukemia therapy. 

Dr. Hitzler is coordinating the activity of the multidisciplinary SickKids Leukemia Research Group (LRG), which brings together investigators with a wide range of expertise who are focused on leukemia (e.g., experimental models of B precursor ALL, TL, AMKL, cell signaling, preclinical testing of experimental agents, supportive care and late effects of leukemia treatment to name a few areas of interest). The LRG provides a forum for exchange and collaborations with the aim to advance the understanding of blood cell cancers and to contribute to the discovery of better treatment.  For information about LRG, please visit the LRG website

External Funding

  • Canadian Cancer Society Research Institute (CCSRI)
  • Canadian Institute of Health Research (CIHR)
  • National Institutes of Health (NIH)
  • Ontario Ministry of Health Drug Innovation Fund
  • Canadian Cancer Society, Ontario Division


  • 2008 & 2012 - Teaching Award: The Hospital for Sick Children, Division of Haematology/Oncology
  • 2009 - Schwartz-Reisman Visiting Sickkids Scholar Award
  • 2007 - Ontario Research of the Month (August), Canadian Cancer Society


For a complete list of publications, please see PubMed

Teuffel O, Kuster SP, Hunger SP, Conter V, Hitzler J, Ethier MC, Shah PS, Beyene J, Sung L. (2011) Dexamethasone versus prednisone for induction therapy in childhood acute lymphoblastic leukemia: a systematic review and meta-analysis. Leukemia. 25(8):1232-8.

Chen J, Li Y, Doedens M, Wang P, Shago M, Dick J, Hitzler J. (2010) Functional differences between myeloid leukemia–initiating and transient leukemia cells in Down syndrome. Leukemia.  24(5):1012-7  

Zwaan CM, Reinhardt D, Hitzler J, Vyas P. (2009) Acute leukemias in children with Down syndrome. Hematology/Oncology Clinics of North America. (1):19-34.

Shah N, Al-Ahmari A, Al-Yamani A, Dupuis L, Stephens D, Hitzler J. (2009) Outcome and toxicity of chemotherapy for acute lymphoblastic leukemia in children with Down syndrome. Pediatric Blood and Cancer.  52:14–19  

Hitzler J, Zipursky A. (2005) Origins of leukemia in children with Down syndrome. Nature Reviews Cancer. 5(1):11-20.  

Lightfoot J, Hitzler J, Zipursky A, Albert M, Macgregor PF. (2004) Distinct gene signatures of transient and acute megakaryoblastic leukemia in Down syndrome.  Leukemia. 18(10):1617-23.  

Hitzler J, Cheung J, Li Y, Scherer SW, Zipursky A. (2003) GATA1 mutations in transient leukemia and acute megakaryoblastic leukemia of Down syndrome.  Blood. 101(11):4301-4.              

Ma Z, Morris SW, Valentine V, Li M, Herbrick JA, Cui X, Bouman D, Li Y, Mehta PK, Nizetic D, Kaneko Y, Chan GC, Chan LC, Squire J, Scherer SW, Hitzler J. (2001) Fusion of two novel genes, RBM15 and MKL1, in the t(1;22) (p13;q13) of acute megakaryoblastic leukemia. Nature Genetics. 28:220-221.