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Leonard Horwitz, MD


Leonard Horwitz, MD
Department: Hematology and Oncology
Location: Cleveland Clinic Main Campus
Mail Code R35
9500 Euclid Avenue
Cleveland, OH 44195
Adults Only

Biographical Sketch

Leonard J. Horwitz, MD, is on Staff in the Department of Hematologic Oncology & Blood Disorders at Cleveland Clinic's main campus. He accepted that appointment in 2007. He had been an assistant professor of medicine in the Section of Bone Marrow Transplantation at M. D. Anderson Hospital in Houston, Texas from 1984 to 1989. He thereafter entered private practice in hematology/oncology in Cincinnati, Ohio until coming to Cleveland Clinic. He served as director of the bone marrow transplant unit for Jewish Hospital of Cincinnati from 1989 to 2003.

His clinical interest lies in non-malignant blood disorders. He no longer does bone marrow transplants.

He graduated magna cum laude from Yale University in New Haven, Conn., and received his medical degree from Albert Einstein College of Medicine, Bronx, N.Y. He completed a residency in internal medicine and fellowship in hematology at Long Island Jewish Hospital, New Hyde Park, N.Y. Dr. Horwitz completed a second fellowship in medical oncology at MD Anderson Hospital & Tumor Institute in Houston, Texas. He is licensed to practice medicine in Ohio.

Dr. Horwitz is a member of the American Medical Association, American College of Physicians (fellow) and American Society of Clinical Oncology, among others. He is board-certified in hematology and in medical oncology and by the American Board of Internal Medicine.




Education & Fellowships

Fellowship - University of Texas M.D. Anderson Cancer Center
Medical Oncology
Houston, TX USA
Fellowship - Long Island Jewish Medical Center
New Hyde Park, NY USA
Residency - Long Island Jewish Medical Center
Internal Medicine
New Hyde Park, NY USA
Internship - Long Island Jewish Medical Center
Internal Medicine
New Hyde Park, NY USA
Medical School - Albert Einstein College of Medicine
New York, NY USA
Undergraduate - Yale University
New Haven, CT USA


  • Internal Medicine- Hematology
  • Internal Medicine
  • Internal Medicine- Medical Oncology

Specialty Interests

Benign hematologic disorders, coagulation disorders, monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma, leukemia, cancer, myelodysplastic syndrome, MDS, anemia

Awards & Honors

Fellow of the American College of Physicians


American Society of Hematology
American Society of Clinical Oncology
American College of Physicians

Treatment & Services

Specialty in Diseases and Conditions

Industry Relationships

Cleveland Clinic physicians and scientists may collaborate with the pharmaceutical or medical device industries to help develop medical breakthroughs or provide medical expertise or education. Cleveland Clinic strives to make scientific advances that will benefit patient care and support outside relationships that promise public benefit. In order for the discoveries of Cleveland Clinic physicians' and scientists' laboratories and investigations to benefit the public, these discoveries must be commercialized in partnership with industry. As experts in their fields, Cleveland Clinic physicians and scientists are often sought after by industry to consult, provide expertise and education.

To assure professional and commercial integrity in such matters, Cleveland Clinic maintains a program that reviews these collaborations and, when appropriate, puts measures in place to minimize bias that may result from ties to industry. The Cleveland Clinic publicly discloses the names of companies when (i) its physicians/scientists receive $5,000 or more per year (or, in rare cases, equity or stock options) for speaking and consulting, (ii) its physicians/scientists serve as a fiduciary, (iii) its physicians/scientists receive or have the right to receive royalties or (iv) its physicians/scientists hold any equity interest for the physician's/scientist's role as inventor, discoverer, developer, founder or consultant.* In publicly disclosing this information, the Cleveland Clinic tries to provide information as accurately as possible about its physicians' and scientists' connections with industry.

As of 2/10/2014, Dr. Horwitz has reported no financial relationship with industry that is applicable to this listing. In general, patients should feel free to contact their doctor about any of the relationships and how the relationships are overseen by the Cleveland Clinic. To learn more about the Cleveland Clinic's policies on collaborations with industry and innovation management, go to our Integrity in Innovation page.

Public Health Service-Reportable Financial Conflicts of Interest. Cleveland Clinic scientists and physicians engage in basic, translational and clinical research activities, working to solve health problems, enhance patient care and improve quality of life for patients. Interactions with industry are essential to bringing the researchers’ discoveries to the public, but can present the potential for conflicts of interest related to their research activities. Click here to view a listing of instances where Cleveland Clinic has identified a Public Health Service (PHS)-Reportable Financial Conflict of Interest and has put measures in place to ensure that, to the extent possible, the design, conduct and reporting of the research is free from bias.

* Cleveland Clinic physicians and scientists subscribe to the guidance presented in the PhRMA Code on Interactions with Healthcare Professionals and the AdvaMed Code of Ethics on Interactions with Health Care Professionals. As such, gifts of substantial value are generally prohibited.

Languages Spoken

  • English
  • Hebrew