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Disease Profile


Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.



US Estimated


Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Solitary reticulohistiocytosis; Solitary histiocytoma


Reticulohistiocytoma (RH) is a rare benign lesion of the soft tissue. It belongs to a group of disorders called non-Langerhans cell histiocytosis and is a type of reticulohistiocytosis, all of which are types of histiocytosis.[1][2] Histiocytosis is a condition in which there is rapid production (proliferation) of histiocytes (immune cells) in the skin or soft tissues.[3] The stimulus that causes the immune system to react in RH is currently not well understood.[1] RH present as a yellow to reddish-brown smooth surfaced, firm nodule or lesion on the trunk and/or extremities of the body.[2] Historically, RH has been found in young adults, with a slightly higher incidence in males.[1] RH typically resolve spontaneously over a period of months to years, are not associated with systemic disease, and do not otherwise affect health. Treatment involves surgical removal of the lesion.[4]


While it is known that reticulohistiocytoma (RH) develop due to a rapid production of immune cells (histiocytes) in the skin or soft tissues, the cause of this process is not currently known.[5][1]


The diagnosis of reticulohistiocytoma (RH) is made based on clinical presentation, histology, and immunohistochemistry profile. RH occur in isolation and are typically described as small, yellow to reddish-born nodules. The lesions usually are slightly elevated from the surrounding skin.[5][4][2] Detailed information on histology of reticulohistiocytoma is available through DermNet NZ, an online resource about skin diseases developed by the New Zealand Dermatological Society Incorporated.

There are several differential diagnoses for RH. It is important to distinguish RH from Rosai-Dorfman disease, juvenile xanthogranuloma, a variety of granulomatous conditions, and some malignant neoplasms, including histiocytic sarcoma, melanoma, and epithelioid sarcoma.[5]

Reticulohistiocytoma should also be distinguished from multicentric reticulohistiocytosis. [4]


Reticulohistiocytoma (RH) typically resolve spontaneously over a period of months to years; however, surgical excision usually results in a cure.[4]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Providing General Support

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

    • DermNet NZ is an online resource about skin diseases developed by the New Zealand Dermatological Society Incorporated. DermNet NZ provides information about this condition.

      In-Depth Information

      • PubMed is a searchable database of medical literature and lists journal articles that discuss Reticulohistiocytoma. Click on the link to view a sample search on this topic.


        1. Heather M. Weissman, Brent R. Hayek, Hans E. Grossniklaus. Reticulohistiocytoma of the Orbit. Ophthal Plast Reconstr Surg. August 25, 2015; 31(1):e13-e16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4548269/.
        2. A. Tulin Gulec. Solitary reticulohistiocytoma with arborizing vessels: A new mimicker of basal cell carcinoma. Journal of the American Academy of Dermatology. January 2016; 74(1):e5-e6. https://www.ncbi.nlm.nih.gov/pubmed/26702812.
        3. Histiocytosis. MedlinePlus. 6/9/2014; https://www.nlm.nih.gov/medlineplus/ency/article/000068.htm.
        4. Reticulohistiocytosis. DermNet NZ. Dec 28, 2013; https://www.dermnetnz.org/dermal-infiltrative/reticulohistiocytosis.html.
        5. Miettinen M, Fetsch JF. Reticulohistiocytoma (solitary epithelioid histiocytoma): a clinicopathologic and immunohistochemical study of 44 cases. Am J Surg Pathol.. 2006; https://www.ncbi.nlm.nih.gov/pubmed/16625100.
        6. Philip R. Cohen, Robert A Lee. Adult-onset reticulohistiocytoma presenting as a solitary asymptomatic red knee nodule: report and review of clinical presentations and immunohistochemistry staining features of reticulohistiocytosis.. Dermatol Online J. March 17, 2014; 20(3):https://www.ncbi.nlm.nih.gov/pubmed/24656263.

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