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 RHD's, 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 can potentially 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.

Inclusion Criteria:

- Any age at diagnosis.

- Diagnosis of a rare histiocytic disorder, established before or after the opening of
the registry.

- 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 they are contacted at least 6 months
after the death of their child and not on their child's birthday or anniversary of
death.

Exclusion Criteria:

- Informed consent has not been signed.

- Diagnosis other than RHD.

- Patients with no pathology sample available for central review.

- Cases diagnosed before the year 1995