Multicentric reticulohistiocytosis (MRH) is a rare disease in which papulonodular skin lesions containing a proliferation of true histiocytes (macrophages) are associated with arthritis. The arthritis involves the interphalangeal joints and becomes severe enough to cause severe destruction of the joints (known as arthritis mutilans) in 45% of cases (see Media File 1). The disease can involve the bones, the tendons, the muscles, the joints, and nearly any other organ (eg, eyes, larynx, thyroid, salivary glands, bone marrow, heart, lung, kidney, liver, gastrointestinal tract). It has been associated with an underlying internal malignancy in about one fourth of cases, suggesting that MRH may be a paraneoplastic condition. The proliferating histiocytes in this disease are thought to be reactive and are not themselves malignant. Also see Multicentric Reticulohistiocytosis.
* Skin nodules * Mucosal nodules * Subcutaneous nodules * Synovial nodules * Periosteal nodules * Bone nodules * Deforming polyarthritis * Itching * Weakness * Fever * Pins and needles sensation * Xanthelasma * Hypertension * Enlarged lymph nodes * High blood lipid level
Most cases of MRH are of unknown cause, but, in about 28% of cases, the disease appears to be caused by a paraneoplastic disorder related to an underlying malignancy. MRH precedes the development of cancer in 73% of cases. Whether the malignancy is truly related to MRH is debated for several reasons. * No consistent type of neoplasm is associated with MRH. Most of the reported specific cancer types are reported less than 5 times each in the literature. * Because MRH is rare, a reporting bias exists in the literature toward reporting those cases with underlying malignancy, especially previously unreported malignancies. Some of these associations may be a coincidence. * The activity of the arthritis and the skin lesions of MRH may or may not be correlated with the eradication of the cancer, unlike some paraneoplastic disorders where removal of the malignancy may produce improvement in the paraneoplastic findings. * Some patients with MRH have been extensively studied or an autopsy has been performed with no evidence of cancer. * MRH has been reported with cancer of the breast (scirrhous, intraductal, unspecified types), cervix, colon (adenocarcinoma), stomach (adenocarcinoma), lung (bronchogenic carcinoma, mesothelioma of pleura), bronchus, larynx, ovary (medullary carcinoma, adenocarcinoma),1 lymphoma, leukemia, sarcoma (omentum, axilla), and melanoma. MRH has also been reported with cancers of unknown primary.
Radiographic findings in multicentric reticulohistiocytosis are different than those in rheumatoid arthritis since there is involvement of the joints distally. Multicentric reticulohistiocytosis can also be differentiated from other arthritides due to the absence of juxtaarticular osteoporosis and periosteal reaction. The erosive pattern seen in gout and psoriatic arthritis is unlike multicentric reticulohistiocytosis due to their asymmetric distribution. Furthermore, calcified soft tissue nodules and overhanging edges are findings in gout which are not seen in multicentric reticulohistiocytosis.