International Rare Histiocytic Disorders
Registry (IRHDR)


Histiocytoses are rare diseases caused by an excess of cells called histiocytes, which can infiltrate the skin, bones, lungs, liver, spleen and the central nervous system. These disorders can range from localized involvement that resolves spontaneously, to progressive disseminated forms that can be debilitating and sometimes life-threatening. The rare histiocytic disorders (RHD), or non-Langerhans cell disorders, are a diverse group of disorders defined by the accumulation of histiocytes that do not meet the criteria for Langerhans cell histiocytosis (LCH) or hemophagocytic lymphohistiocytosis (HLH). They include: Juvenile xanthogranuloma family, Erdheim-Chester disease, Multifocal Reticulohistiocytosis, Rosai-Dorfman disease and the Malignant Histiocytoses. Since they are so rare, there is limited understanding of their causes and treatments. Physicians, patients and parents of children with rare histiocytoses frequently consult members of the Histiocyte Society on the management of these disorders. Very often, no specific recommendation about treatment can be made due to the lack of prospective outcome data for these rare entities. The creation of an International Rare Histiocytic Disorders Registry (IRHDR) will facilitate a uniform diagnosis of the RHDs, as well as the collection and analysis of the clinical, epidemiological, treatment and survival data of patients with RHD. The registry will also provide expert pathology reviews and may lead to future therapeutic recommendations. Furthermore, the IRHDR can provide a framework for future clinical trials, thus, creating excellent research opportunities. Lastly, a de-identified link between clinical data and companion biology studies may be accomplished in the future through the IRHDR. This may further help in understanding the etiology of these rare diseases, as well as identifying potential therapeutic targets.

Eligibility to participate in the IRHDR:

  • Research participants are defined as those who provide demographic, clinical and treatment data for research.
  • Research participants may be enrolled at the Hospital for Sick Children, Toronto, Canada and at any collaborating institution that seeks ethics approval for this registry. Local IRB approval of this study must be obtained by a site prior to enrolling patients.
  • The research participant can be a patient with a rare histiocytic disorder, or the parent of a patient with minor status with a rare histiocytic disorder. 

Subject Inclusion Criteria for IRHDR:

  • Diagnosis of a rare histiocytic disorder, established before or after the opening of the registry (retrospective and/or prospective).
  • Any age at diagnosis.
  • Cases diagnosed from January-01-1995 until the present time and prospectively.
  • Suitable pathology sample available for central review.
  • Signed informed consent by a patient, or parent/legal guardian.
  • Cognitively impaired patients can be included after consent by legal guardian/parent.
  • Deceased patients can be included provided that their families are contacted at least 6 months after the death of their child and not on their child’s birthday or anniversary of death. 

Procedures to enroll a subject in the IRHDR:

Consent Procedures: Local and Outside Patients

  • Patient or parent obtains consent form from the study coordinators (for local patients) or from the submitting physician.
  • Study coordinators will review consent forms directly with local patients/parents and will obtain their consent.
  • In case of non-local patients or non-English-speaking participants, the consent can be obtained with the help of an international delegate.
  • Participating centers submit signed consent and medical records release forms to the study coordinators via fax (416-813-5327) or Email (

Data Collection & Submission

  • The study coordinator contacts patients’ physicians, and submits list of requested documents and samples.
  • The selected documents are faxed or e-mailed to study coordinator.
  • Patients’ data will be entered directly on REDCAP website by the submitting physician; subsequently the study PI and CRA will check the data before loading them permanently into the database.

Data To Be Collected

The following documents and samples will be requested by the study coordinator from the patient’s health care provider(s):
  • Pathologist’s report on diagnostic pathology specimens
  • Clinical summary by the treating physician (possibly in English)
  • Pathology specimens for review by the registry designated pathologist


Each patient will be assigned a study identification number (ID); identifying information such as patients’ names and medical record numbers will then be stripped from the medical documents, and no identifying information other than the patients’ IDs will be stored in the database. A separate record which links patient identifiers with their ID will be maintained in a secure protected environment by the project PI.  

Procedures For Sending Pathology Samples To The Designated Pathology Reviewer: 

Cases cannot be submitted or accepted for pathological review until evidence of ethics board approval from the referring center is provided to the IRHDR coordinator at SickKids.

North American Central Pathology Review Center
Samples from cases diagnosed in North America will be reviewed by Dr. Ronald Jaffe and Dr. Jennifer Picarsic and shipped to Children's Hospital of Pittsburgh of UPMC:

Jennifer Picarsic, MD
Children's Hospital of Pittsburgh of UPMC,
Main Hospital, Dept of Pathology, Room B260
4401 Penn Ave
Pittsburgh, PA 15224
South American Central Pathology Review Center
Those diagnosed in South America, Australia/New Zealand or Africa will be shipped to Dr Laura Galluzzo:

M. Laura Galluzzo Mutti
Patóloga Pediátrica
Htal Nacional de Pediatría Dr Prof J. P Garrahan
Combate de los Pozos 1881. CP 1245
Buenos Aires, Argentina
European Central Pathology Review Center
Cases from Europe will be shipped to Jean-François Emile, MD, PhD:

Jean-François Emile, MD, PhD
Service de pathologie
Hopital Ambroise Paré
9 Av. Charles de Gaulle
92104 Boulogne France
  1. Material for review can be sent by courier directly from the submitting center to the reviewer identified by the registry. It must include the Institutional Pathology Report (even if incomplete), clinical summary and glass slides:  1 H&E and 10 unstained slides for immunostains (or a tissue block).
  2. The reviewer will get additional stains if needed for diagnosis and prepare a report that will be faxed to the registry.
  3. Original slides will be returned directly from the reviewer to the submitting center.
  4. Shipping charges and immunostain fees will be reimbursed by the registry. All invoicing questions can be sent to
  5. If possible, one shipping of all retrospective cases at each center is preferred.


For questions or to register for the IRHDR, contact:

The IRHDR is registered with NCT02285582.



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