Multicentric Reticulohistiocytosis With Arthralgia and Red-Orange Papulonodules

Cutaneous findings of MRH can mimic rheumatoid nodules, gout, Gottron papules of dermatomyositis, lipoid proteinosis, sarcoidosis, lepromatous leprosy, granuloma annulare, xanthoma, xanthogranuloma, and fibroxanthoma.^6,7 Histopathologic features may distinguish MRH from such entities. Findings include fairly well-circumscribed aggregates of large multinucleated giant cells with characteristic eosinophilic ground-glass cytoplasm. Histiocytes stain positively for CD68, HAM56, CD11b, and CD14, and variably for factor XIIIa. CD68, which is expressed by monocytes/macrophages, has been universally reported to be the most reliable marker of MRH. Negative staining for S-100 and CD1a supports a non-Langerhans origin for the involved histiocytes. If arthritic symptoms predominate, MRH must be distinguished from rheumatoid and psoriatic arthritis.^6,7

Mucosal involvement occurs in approximately 50% of patients and includes the presence of nodules in the oral, nasal, and pharyngeal mucosae, as well as eye structures.^2,3 Histiocytic infiltration has been documented in the heart, lungs, thyroid, liver, stomach, kidneys, muscle, bone marrow, and urogenital tract. Histiocytes also can invade the cartilage of the ears and nose causing disfigurement and characteristic leonine facies. Pathologic fractures may occur with bone involvement.⁵

Systemic features associated with MRH include hyperlipidemia, diabetes mellitus, thyroid disease, hypergammaglobulinemia, and various autoimmune diseases. Patients less frequently report fever and weight loss.^2,5,6,8 Additionally, a positive tuberculin test occurs in 12% to 50% of patients.⁶ Various autoimmune diseases occur in 6% to 17% of cases including systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, dermatomyositis, Sjögren syndrome, and primary biliary cirrhosis.^2,5,6,8 The most clinically salient feature of MRH is its association with malignant conditions, which occur in up to 31% of patients. A variety of cancers have been reported in association with MRH, including breast, cervical, ovarian, stomach, penile, lymphoma, mesothelioma, and melanoma.⁷

The etiology of MRH is unclear. Although onset may precede the development of a malignant condition and regress with treatment, it cannot be considered a true paraneoplastic disorder, as it has no association with a specific cancer and does not typically parallel the disease course.^6,9 Reports of increased levels of inflammatory mediators released from macrophages and endothelial cells, specifically IL-12, IL-1β, IL-6, and tumor necrosis factor α (TNF-α), have been thought to drive the destruction of bone and cartilage.⁶ In particular, TNF-α acts to indirectly induce destruction by stimulating proteolytic activity in macrophages, similar to the pathogenesis of joint damage in rheumatoid arthritis.⁸ Osteoclastic activity may play a role in the pathogenesis of MRH, as multinucleated giant cells in MRH can mature into osteoclasts by receptor activated nuclear factor–κB ligand signaling. In addition, patients treated with bisphosphonates have had decreased lacunar resorption.^2,8

Initial management of MRH should include screening for hyperlipidemia, hypergammaglobulinemia, hyperglycemia, thyroid dysfunction, and autoimmune diseases, as well as age-appropriate cancer screening. Imaging studies should evaluate for the presence of erosive arthritis. There are no well-defined treatment algorithms for MRH due to the rarity of the disease, and recommendations largely rely on case reports. Although spontaneous remission typically occurs within 5 to 10 years, the risk for joint destruction argues for early pharmacologic intervention. Current management includes the use of nonsteroidal anti-inflammatory drugs and various immunosuppressants including oral glucocorticoids, cyclophosphamide, chlorambucil, methotrexate, or azathioprine.² A combination of methotrexate with cyclophosphamide or glucocorticoids also has shown efficacy.¹⁰ Anti–TNF-α agents, such as etanercept, adalimumab, and infliximab, have been used with some success.² Tumor necrosis factor α inhibitors used in combination with oral glucocorticoids and methotrexate may have an increased benefit.^2,9,11 Evidence suggesting that TNF-α plays a role in the destruction of bone and cartilage led to the successful use of infliximab in combination with oral glucocorticoids and methotrexate, which prevented possible development of antibodies to infliximab and increased its efficacy.¹² Bisphosphonate use in combination with glucocorticoids and methotrexate may prevent joint destruction without the serious adverse events associated with anti–TNF-α agents.^2,9,13,14