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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.


  • 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. 
  • 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. If local IRB approval is required by submitting physician center, this must be obtained prior to enrolling patients.
  • Participants do not have to be patients at referring sites, and can participate in the biobank and registry portions through telephone consent.


  • 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.
  • 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. 
  • 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. 


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 via telephone or with the help of an international delegate.
  • Participating centers submit signed consent and medical records release forms to the study coordinators via fax (416-813-8897) or Email ( or
Data Collection and 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
  • Brief clinical summary by the treating physician (possibly in English)
  • Pathology specimens for review by the registry designated pathologist

Participants may choose to take part in a sub-study that is an optional component of the main registry study. The main registry study collects information about patients with rare histiocytic disorders (RHD). The biobank sub-study stores and banks patients’ samples for future research studies to learn about, prevent, or treat rare histiocytic disorders.


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.  


Cases cannot be submitted or accepted for pathological review until consent has been obtained by participants.

North American Central Pathology Review Center *Please note new shipping address as of 1/19/2023

Samples from cases diagnosed in North America will be reviewed by Dr. Jennifer Picarsic and shipped to Cincinnati Children's Hospital Medical Center:
Jennifer Picarsic, MD
Cincinnati Children’s Hospital Medical Center (CCHMC) | Pathology and Lab Medicine | R2040
240 Albert Sabin Way, S Dock | Cincinnati, OH  45229-3026
Cincinnati, OH 45229 USA

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

  • 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).
  • The reviewer will get additional stains if needed for diagnosis and prepare a report that will be faxed to the registry.
  • Original slides will be stored at The Hospital for Sick Children Biobank, if the optional biobank study has been consented to. If the optional biobank study is declined, slides will be returned directly from the reviewer to the submitting center.
  • Shipping charges and immunostain fees will be reimbursed by the registry. All invoicing questions can be sent to
  • If possible, one shipping of all retrospective cases at each center is preferred.


For questions or to register for the IRHDR contact or

The IRHDR is registered with NCT02285582

Updated July 2019

Office: +1 (856) 589-6606
Fax: +1 (856) 589-6614

Histiocyte Society
332 N Broadway
Pitman, NJ 08071 USA

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