Multicentric reticulohistiocytosis (MRH): case report with review of literature between 1991 and 2014 with in depth analysis of various treatment regimens and outcomes

Multicentric reticulohistiocytosis post-COVID-19: a case report

Background

Multicentric reticulohistiocytosis (MRH) stands as a rare and challenging systemic granulomatous disease characterized by its predilection for skin and joint involvement, confounding clinicians with its infrequent presentation and systemic manifestations.

Case Description

This compelling case presentation unravels the intricate complexity of MRH, exemplifying its unique clinical course. Following mild upper respiratory coronavirus disease 2019 (COVID-19) symptoms, the patient manifested purplish-pink papular lesions on both the skin and mucosa, accompanied by debilitating arthralgias. A diagnostic skin biopsy, a pivotal tool in MRH diagnosis, confirmed the presence of this granulomatous disorder, underlining its systemic impact. Strategic therapeutic intervention involving a combination of steroids and methotrexate demonstrated remarkable efficacy, culminating in the resolution of symptoms within 3-month. The absence of malignancy upon thorough screening further amplifies the perplexing nature of MRH.

Conclusions

This seminal case not only bridges the realms of rare systemic disorders but also marks the first known instance of MRH emerging post-COVID-19. It underscores the imperative consideration of MRH in analogous scenarios and provides invaluable insights into the nuanced interplay of MRH symptoms, diagnosis, and therapeutic strategies following viral triggers. This comprehensive exploration enriches our scientific understanding, offering nuanced perspectives on the manifestations and intricate dynamics of MRH in the context of post-viral sequelae.

A case report of multicentric reticulohistiocytosis with atypical cutaneous presentation

Multicentric reticulohistiocytosis (MRH) is a rare systemic disorder characterized by histiocytic hyperplasia that mainly involves the skin, mucous membranes, and joints. The typical clinical features include papules, nodules, and arthritis. MRH lesions are relatively extensive but small and scattered. Joint inflammation is characterized by diffuse symmetric polyarthritis as the first symptom, which can be severe and disabling due to destructive joint changes. MRH is easily misdiagnosed in clinical practice. Here, we report the case of an elderly male patient who presented with polyarticular pain in the hip and interphalangeal joints as the first manifestation, followed by the development of large, isolated, bulging skin nodules, which are atypical MRH lesions. This is rare in all MRH case reports, and we made the correct diagnosis by combining skin histopathology, immunohistochemistry, and other clinical examinations. We performed surgical treatment on the local skin lesions of this patient. This case suggests that clinicians should actively correlate the condition and accurately diagnose MRH when encountering atypical skin changes or other diseases as the first symptom and explore the mechanisms of MRH and other clinical manifestations.

Multicentric Reticulohistiocytosis Presenting As Acute Pericarditis With Moderate-Sized Pericardial Effusion: A Case Report and Review of Multicentric Reticulohistiocytosis Treatment

Multicentric reticulohistiocytosis (MRH) is a rare, class IIb non-Langerhans cell histiocytosis associated with skin and joint involvement. It is more prevalent (80%) in Caucasian females in their fifth to sixth decade of life. Patients usually demonstrate symptoms and signs of symmetric polyarthritis and papulonodular cutaneous lesions. In addition to skin and joints, multiple organs can be involved, such as the lung (pleural effusion, interstitial fibrosis, hilar lymphadenopathy), heart (pericardial effusion, myocarditis), gastrointestinal system, and urogenital system (genital tract and kidney). Pericardial involvement is a rare manifestation, and around three cases have been reported in the literature so far. Our case report is a valuable contribution to the literature, which aids clinicians in contemplating MRH as one of the differentials among patients presenting with pericardial effusion. We described the characteristics of MRH along with its differentiating features from other autoimmune conditions and management.

Multicentric reticulohistiocytosis: A diagnostic challenge

Multicentric reticulohistiocytosis, also called as lipoid dermato-arthritis is a rare form of non-Langerhans cell histiocytosis characterised by nodular and papular skin lesions containing characteristic bizarre multinucleate giant cells with ground glass cytoplasm. The disease commonly involves the skin, mucosa, synovium, and internal organs with cutaneous nodules and progressive erosive arthritis being the most common presenting features. We report a case of a 61-year-old male presenting with multiple swellings over distal part of fingers for 6 years without involvement of joints. A diagnosis of multicentric histiocytosis was made based on typical histopathological features of sheets of histiocytes and multinucleate giant cells with ground glass eosinophilic cytoplasm. The disease has a low incidence and about 300 cases have been reported so far in literature. The present case is being reported as it is uncommon for the disease to present in absence of arthritis.

Multicentric reticulohistiocytosis with eosinophilic gastroenteritis: An unusual relationship

Multicentric reticulohistiocytosis (MRH) is a rare disease with poorly defined therapeutic strategies. Here, we report the case of a patient with eosinophilic gastroenteritis who developed MRH after 5 years. The patient presented with disabling and rapidly progressive polyarthralgia, eosinophilic gastroenteritis, and resistance to first-line therapies. However, there was a marked improvement in the arthritis symptoms following treatment with tofacitinib. This presentation provides a useful perspective for the therapeutic management of complex scenarios involving MRH.

A Novel Case of Multicentric Reticulohistiocytosis Associated with Renal Cell Carcinoma Successfully Treated with Infliximab and Methotrexate

Multicentric reticulohistiocytosis (MRH) is categorized as a rare non-Langerhans cell histiocytosis most commonly seen in women in the fourth to fifth decade of life. This systemic inflammatory condition affects multiple organ systems and can result in severe joint destruction which can progress to arthritis mutilans. To date, various underlying malignancies have been discovered in patients with MRH including breast, gastric, thymic, hepatic, and melanoma. There has been 1 case of underlying renal cell carcinoma reported in a patient diagnosed with MRH. Additionally, there is no consistently recognized treatment for MRH described in the literature. The rarity of the disease contributes to the difficulty in defining a standardized treatment. We present the case of a patient with extensive joint and skin involvement who was successfully treated with infliximab and methotrexate, experienced clinical improvement, and was later diagnosed with clear cell renal cell carcinoma. The synergistic effects of infliximab and methotrexate, in combination with the low side-effect profile, appear to be promising in the setting of MRH and in our patient resulted in the resolution of symptoms and cutaneous manifestations. We suggest this regimen as an effective combination therapy. We emphasize thorough and continuous screening for underlying malignancy associated with MRH, despite clinical improvement or negative malignancy work-up upon initial diagnosis.

Multicentric Reticulohistiocytosis Associated with an Early Form of Systemic Lupus Erythematosus: A Case Report of a Rare Disease, with Mini Review of the Literature

Multicentric reticulohistiocytosis (MRH) is the most frequently described form of reticulohistiocytosis (RH), and it is classified as a class IIb non-Langerhans cell histiocytosis. It has been designated as multicentric, being characterized by multisystemic involvement. In fact, although mainly involving the skin, along with the joints, it is a systemic inflammatory condition potentially involving every internal organ. As MRH-related skin findings can mimic rheumatoid nodules or Gottron papules, the histopathology of the cutaneous lesions is often necessary for the correct diagnosis. Approximately one-third of MRH patients have confirmed concomitant autoimmune disorders. A wide variety of autoimmune disorders associated with the disease have been reported in the literature, suggesting immune dysfunction as a factor in the pathophysiology of MRH. A case of MRH associated with autoimmune manifestation is reported in the context of a mini review of the literature, with a focus on clinical presentation, treatments, and treatment outcomes. Moreover, eight cases of MRH associated with autoimmune diseases are briefly discussed.

Successful Treatment of a Patient with Rheumatoid Arthritis and Comorbid Multicentric Reticulohistiocytosis

Multicentric reticulohistiocytosis (MRH) is a rare disease of unknown pathogenesis, characterized by skin histiocytosis and destructive arthritis. The present study describes a 53-year-old woman who presented with rheumatoid arthritis (RA) and MRH, which is a clinically rare entity. Diagnosis of MRH was based on nodule pathology. Meanwhile, the patient had typical arthritis, was positive for serum anti-cyclic citrullinated peptide (anti-CCP) antibodies and synovitis confirmed by joint ultrasound, and was diagnosed with RA. Her symptoms resolved with glucocorticoids and methotrexate.

Multicentric reticulohistiocytosis with prominent skin lesions and arthritis: A case report

BACKGROUND

Multicentric reticulohistiocytosis (MRH) is a rare non-Langerhans histiocytosis of unknown etiology characterized by papulonodular skin lesions and progressive, erosive arthritis. To date, there have been approximately 300 cases of MRH reported worldwide. The majority of patients are Caucasian from western countries, and Asian patients are rare. Here, we report a case of MRH in a Chinese patient.

CASE SUMMARY

A 38-year-old male was admitted to the hospital with a rash that had persisted for over 2 years and bilateral knee pain for over 1 year. The patient’s symptoms had previously been misdiagnosed as eczema when there were only skin symptoms and was finally diagnosed as MRH after a skin biopsy of the left upper back. The patient was treated with glucocorticoids combined with an immunosuppressive regimen. While the skin lesions on both arms, abdomen, and back subsided, the skin lesions on the rest of the body did not increase. The interphalangeal joints of both thumbs and bilateral knee joints remained swollen and painful.

CONCLUSION

The case will help clinicians better identify and treat this disease in the absence of epidemiological studies or randomized controlled data.

Coral red beads and arthritis

We report a patient presenting with cutaneous papulonodular lesions associated with painful stiff joints. Histopathological examination showed positivity for CD68 and CD45. There was no atypia.

Skin Manifestation Associated With Multicentric Reticulohistiocytosis

ABSTRACT

Multicentric reticulohistiocytosis (MRH) is a rare multisystem disorder, primarily affecting the skin and joints. As severe joint damage is a possible symptom, early diagnosis and therapeutic intervention are required. Cutaneous lesions present with characteristic features such as discrete reddish nodules, especially on acral locations. Additionally, the face, scalp, trunk and extremities are also affected. Xanthomatous plaques are also seen on the face. The cutaneous manifestations of MRH are various, which therefore should be differentiated from several diseases. In particular, MRH has been reported to assume clinical appearances resembling Gottron papules, periungual erythema, V-neck erythema, shawl sign, and poikiloderma associated with dermatomyositis. Histopathologic features show proliferation of multinucleated giant cells with abundant eosinophilic granular ground glass-like cytoplasm in the dermis. Multicentric reticulohistiocytosis is occasionally paraneoplastic and is associated with internal malignancies. The appropriate therapies are still challenging, and oral prednisolone, immunosuppressants, and recent biologics are used. In this article, cutaneous lesions, histopathology, and pathogenesis of MRH are mainly discussed from a dermatological perspective. It is important, not only for dermatologists but also for rheumatologists and orthopedists, to be able to distinguish between the various types of skin lesions brought on by MRH. Cutaneous signs are important diagnostic clues and assessment tools for therapeutic efficacy.

[Multicentric reticulohistiocytosis: A case report]

A 65-year-old woman developed erythema, papules and nodules over the body. Some nodules of her auricles and hands like string beads. Besides, she suffered from symmetrical swelling and pain of multiple joints, morning stiffness with deformity of joints; She had elevated erythrocyte sedimentation rate and C reactive protein levels; Her rheumatoid factor and antinuclear antibody were positive; Joints destruction was found with X-ray imaging; Skin pathology showed Dermal infiltrate of abundant histiocytes, part of them with a ground-glass appearance; A CD68 immunohistochemical stain was positive and the cells were negative for S100, CD1a. These findings were diagnostic evidences of multicentric reticulohistiocytosis (MRH). The patient received high-dose of glucocorticoids combinated with immunosuppressive agents, and achieved a satisfactory effect. MRH was a rare multisystem disease characterized by papulonodular mucocutaneous and destructive arthritis, and its pathogeny was not yet completely understood. The typical lesions of MRH were hard papules or nodules that usually occured on the hands, face and arms. Classic coral bead appearance from periungual cutaneous nodules that were characteristic of MRH. MRH was an inflammatory joint disease, affecting almost all the appendicular joints and characterized by joint multiple, symmetrical, destructive, progressive disability. Joints destruction of the distal interphalangeal joints was a unique feature of MRH. In addition to skin and joints, it could also involve other systems. There were no diagnostic laboratory markers for MRH. Laboratory examinations had often been found to be non-specific. Imageological examination mainly showed bone and joint destruction. Skin biopsy was the best test to diagnose MRH, the typical histopathological findings included an infiltrate with histiocytes and multinucleated giant cells with a ground-glass appearing in eosinophilic cytoplasm, and the immunohistochemical stain was positive for CD68. The diagnosis was typically made based on the clinical presentation, supportive radiographic findings and skin biopsy. MRH was easily possible to mistake for other more common autoimmune conditions, such as rheumatoid arthritis, psoriatic arthritis, osteoarthritis, and dermatomyositis, but the distinctive clinical, radiographic, and histologic features could aid in differentiating these diseases. MRH could mimic other rheumatic diseases, besides, it could also coexist with cancer or other autoimmune disorders. There was no standardized treatment for MRH. However, Nonsteroidal anti-inflammatory drugs, glucocorticoid, Immunosuppressant, biologic medications, and bisphosphonates had been used with varying degrees of curative effect. Treatment with glucocorticoid combined with immunosuppressants were effective for rash and arthritis, early use of them should be strongly considered, and refractory cases could be treated with biological agents. By reporting a MRH case and reviewing literature, this paper aims to help the clinicians improve the understanding of this rare disease, and suggests that when one diagnosis cannot explain the whole picture of the disease, and further evidence should be sought to confirm the diagnosis.

Multicentric Reticulohistiocytosis with Dermatomyositis-Like Features: A Case Report with Dermoscopy and Reflectance Confocal Microscopy Findings

Multicentric reticulohistiocytosis is an insidious-onset, non-Langerhans-cell histiocytosis affecting joints and skin. Early diagnosis is important to prevent destructive arthritis and disease-related complications. Reflectance confocal microscopy (RCM) is a technique that allows the visualization of the epidermis and superficial dermis non-invasively on a horizontal plane with quasi-histologic images of the skin. RCM features of non-Langerhans cell histiocytosis including Rosai-Dorfman disease, adult xanthogranuloma (AXG) and, juvenile xanthogranuloma (JXG) have been reported. However, RCM features of MRH have not previously been described. Herein, we present the RCM features of a case of MRH with dermoscopic and histopathologic features. This article is protected by copyright. All rights reserved.

The combined prevalence of classified rare rheumatic diseases is almost double that of ankylosing spondylitis

BACKGROUND

Rare diseases (RDs) affect less than 5/10,000 people in Europe and fewer than 200,000 individuals in the United States. In rheumatology, RDs are heterogeneous and lack systemic classification. Clinical courses involve a variety of diverse symptoms, and patients may be misdiagnosed and not receive appropriate treatment. The objective of this study was to identify and classify some of the most important RDs in rheumatology. We also attempted to determine their combined prevalence to more precisely define this area of rheumatology and increase awareness of RDs in healthcare systems. We conducted a comprehensive literature search and analyzed each disease for the specified criteria, such as clinical symptoms, treatment regimens, prognoses, and point prevalences. If no epidemiological data were available, we estimated the prevalence as 1/1,000,000. The total point prevalence for all RDs in rheumatology was estimated as the sum of the individually determined prevalences.

RESULTS

A total of 76 syndromes and diseases were identified, including vasculitis/vasculopathy (n = 15), arthritis/arthropathy (n = 11), autoinflammatory syndromes (n = 11), myositis (n = 9), bone disorders (n = 11), connective tissue diseases (n = 8), overgrowth syndromes (n = 3), and others (n = 8). Out of the 76 diseases, 61 (80%) are classified as chronic, with a remitting-relapsing course in 27 cases (35%) upon adequate treatment. Another 34 (45%) diseases were predominantly progressive and difficult to control. Corticosteroids are a therapeutic option in 49 (64%) syndromes. Mortality is variable and could not be determined precisely. Epidemiological studies and prevalence data were available for 33 syndromes and diseases. For an additional eight diseases, only incidence data were accessible. The summed prevalence of all RDs was 28.8/10,000.

CONCLUSIONS

RDs in rheumatology are frequently chronic, progressive, and present variable symptoms. Treatment options are often restricted to corticosteroids, presumably because of the scarcity of randomized controlled trials. The estimated combined prevalence is significant and almost double that of ankylosing spondylitis (18/10,000). Thus, healthcare systems should assign RDs similar importance as any other common disease in rheumatology.

Multicentric Reticulohistiocytosis Exhibiting Positive HLA-B*07 and HLA-B*08: A Case Report

Multicentric reticulohistiocytosis (MRH) is a rare cause of destructive inflammatory arthritis involving both small, as well as larger joints. We report the case of a 40-year-old Caucasian female with a family history of neoplasia who was referred to our service witha two-month history of inflammatory joint pain. On examination, the patient had inflammatory arthritis, mainly involving the peripheral joints, sacroiliac joint pain, and numerous papulonodular mucocutaneous lesions, including periungual “coral beads”. Imaging tests revealed erosive arthritis with synovitis and tenosynovitis, sacroiliac joint changes, as well as papulonodular mucosal lesions in the nasal vestibule, the oropharyngeal mucosa, and supraglottic larynx. She tested positive for HLA-B*07 (Human Leukocyte Antigen B*07) and HLA-B*08, ANA (antinuclear antibodies), RF (rheumatoid factor), anti-Ro52, anti-SSA/Ro, and anti-SSB/La antibodies. The skin biopsy was suggestive of MRH, showing a histiocyte infiltrate and frequent giant multinucleated cells. The patient exhibited favorable outcomes under Methotrexate, then Leflunomide. However, she displayed worsening clinical symptoms while under Azathioprine. To our knowledge, this is the first case of MRH to exhibit positive HLA-B*07 together with HLA-B*08. The rarity of MRH, its unknown etiology and polymorphic clinical presentation, as well as its potential neoplastic/paraneoplastic, and autoimmune nature demand extensive investigation.

Multicentric reticulohistiocytosis: A case report with response to adalimumab

Although MRH can mimic rheumatoid arthritis, its ability to rapidly progress to arthritis mutilans and association with malignancy in up to 25% of patients warrant prompt recognition and treatment along with age-appropriate malignancy work-up.

Reticulohistiocytoses: a revision of the full spectrum

Reticulohistiocytoses (RH) are rare and clinically heterogeneous histiocytic disorders of dermatological interest. Three clinical entities with superimposable histopathological features are currently considered, namely solitary reticulohistiocytoma, diffuse/generalized reticulohistiocytosis and multicentric reticulohistiocytosis. Although in the last decade, RH studies have only minimally progressed, histiocytosis research has advanced considerably: the prognostic and therapeutic importance of the clinical subclassification of histiocytosis patients as well as of the detection of genetic alterations in the genes of the ERK pathway has been highlighted. According to these insights, we previously reported the presence of molecular alteration RH and described a subset of patients with disseminated multisystem involvement lacking arthritis. In the present review, we aim to update and revise the knowledge regarding RH. We first reviewed their histopathological, immunophenotypical and ultrastructural features, discussed their histopathological differential diagnosis with other conditions characterized by infiltrates made of oncocytic or epithelioid cells (with special regard to Destombes-Rosai-Dorfman disease) and finally summarized the molecular landscape of RH. We therefore tried to adjust the clinical subclassification of Langerhans cell histiocytosis to the clinical phenotypes of RH, outlining five clinically different groups of patients. Finally, we reconsidered the clinical workflow to the evaluation of RH patients, in light of the 5 different clinical groups and discussed the different therapeutic approaches and the possible role of target inhibitors.

Multicentric Reticulohistiocytosis: Elective Excision of Symptomatic Hand Nodules With 1-Year Follow-Up

Multicentric reticulohistiocytosis is a rare non-Langerhans cell histiocytic rheumatologic disorder characterized by multiple skin lesions, painful hand nodules, and destructive polyarthritis that results in arthritis mutilans in 20% to 30% of patients. In the current literature, there have been approximately 300 cases reported and the pathogenesis remains unclear. Currently, there is no diagnostic serologic test and no consensus on management. In this case report, we present a patient with multicentric reticulohistiocytosis who was treated with selective excision of 3 painful nodules on the hand. The patient was seen 1 year after surgery. One of the nodules reoccurred whereas the other 2 remained quiescent. This procedure has the potential to produce considerable pain relief and improve quality of life in a disease process for which optimal medical regimen remains to be determined.

Multicentric reticulohistiocytosis: the Mayo Clinic experience (1980–2017)

Objectives

Multicentric reticulohistiocytosis (MRH), a rare histiocytic disease that can mimic other rheumatic conditions, may be associated with cancer and other autoimmune disorders. To better understand the disorder and its other associations, we aimed to evaluate clinical correlates and outcomes of all patients with MRH seen at Mayo Clinic, Rochester between 1980 and 2017.

Methods

A retrospective medical record review was conducted to identify all patients with MRH between 1 January 1980 and 30 April 2017.

Results

We identified 24 patients with biopsy-proven MRH (58% female, 75% Caucasian, median age at diagnosis 52 years, median follow-up of 2.3 years). All patients had cutaneous and articular involvement; 23 (96%) patients had papulonodular skin lesions (87% periungual and dorsal hand) and seven (30%) mucosal nodules; and 22 (92%) patients had arthralgias, 21 (88%) joint effusions and 13 (54%) synovitis. Most frequently used therapies included corticosteroids, cyclophosphamide, methotrexate and bisphosphonates. Biologics were used in four patients. Nine patients had symptomatic resolution at 1 year and 12 partial improvement. Radiological findings included erosive changes in three (60%) patients and arthritis mutilans in two patients (40%). Twenty-nine per cent of patients had a concomitant autoimmune disease and 25% malignancy including melanoma, endometrial, peritoneal and lung carcinoma. The 5-year survival rate was 85% (95% CI: 74, 100%).

Conclusion

To our knowledge, this is the largest single-centre series of patients with MRH highlighting the rarity of the condition and an unmet need for treatment options that can allow sustained disease remission. It also highlights the need for a high vigilance for malignancy and autoimmune diseases.

Thalidomide, A Rational Agent for Treatment of Multicentric Reticulohistiocytosis

A patient with Multifocal Reticulohistiocytosis (MRH) of skin and joints failed treatment with etanercept, methotrexate, hydroxychloroquine, prednisone, bisphosphonates and hydroxyzine. Long term treatment with thalidomide led to marked improvement in joint and cutaneous manifestations.

Multicentric reticulohistiocytosis: a case report

Background

Multicentric reticulohistiocytosis is a rare form of non-langerhans cell histiocytosis presenting with skin changes and erosive arthritis. Infiltration of histiocytes and multinucleated giant cells are typical histological findings and confirm the diagnosis.

Case presentation

This case report describes a newly diagnosed case of multicentric reticulohistiocytosis in a healthy 26-year-old female originally from the Philippines. Eruption of papules and nodules on the hands and pain in multiple joints were the main complaints at the initial presentation. Radiographical findings of erosions in the small hand and feet joints were impressive. Initial histological findings did not match the clinical image, although later the clinical diagnosis was supported by histological findings in additional biopsies.

Conclusions

Although initial histological findings did not match the clinical image, additional biopsies were valuable to confirm the diagnosis.

The utility of FDG-PET/CT imaging in the evaluation of multicentric reticulohistiocytosis: A case report

INTRODUCTION

Multicentric reticulohistiocytosis (MRH) is a rare histiocytic disorder that involves the skin, joints, and visceral organs.

CASE PRESENTATION

We report a 67-year-old woman with MRH who presented with a 2-years history of polyarthralgia and skin nodules. Her symptoms were an inflammatory polyarthropathy with punched-out lesions of the distal interphalangeal (DIP) joints of both hands. Doppler ultrasonography of the hands showed large bone erosions with power Doppler signals in the DIP joints. F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) demonstrated increased FDG uptake in cutaneous papules surrounding the affected joints, suggesting an inflammatory process. There was no evidence of malignancy. Biopsy samples of skin nodules exhibited dermal infiltration with CD68-positive histiocytes and multinucleated giant cells. The patient was diagnosed with MRH and treated with combination therapy comprising a steroid (prednisolone), tacrolimus, methotrexate, and infliximab, which resulted in clinical improvement. Following infliximab treatment, there was a significant decrease in a bone resorption marker (tartrate-resistant acid phosphatase 5b: TRACP-5b), suggesting that tumor necrosis factor-α targeting therapy may inhibit osteoclast formation and resorption activity in patients with MRH.

CONCLUSION

MRH is a progressive destructive arthritic condition, and early diagnostic and therapeutic strategies are necessary to improve the outcome. FDG-PET/CT and joint ultrasonography might be noninvasive imaging modalities that could help diagnose MRH.

Looks Can Be Deceiving: A Case Report on Multicentric Reticulohistiocytosis Successfully Treated with Rituximab

Multicentric reticulohistiocytosis (MRH) is an idiopathic multisystemic inflammatory disease characterized by symmetric erosive polyarthritis and typical papulonodular skin lesions. MRH can be associated with autoimmune diseases, malignancy, mycobacterial infections, and hyperlipidemia, and it is important to consider appropriate screening in this population. There is no specific diagnostic laboratory test for MRH. The gold standard for diagnosis is skin or synovial biopsy, which shows characteristic multinucleated non-Langerhans giant cells and ground glass eosinophilic cytoplasm. Although the disease spontaneously remits in approximately 10 years, MRH can rapidly progress to arthritis mutilans in the majority of cases. The diagnosis and treatment are challenging due to its low prevalence and lack of robust guidelines from major rheumatological societies. Corticosteroids and methotrexate are generally first-line treatment options. However, more recently, biologic agents have been increasingly used in refractory cases with some success. Early diagnosis is crucial in preventing disease progression. We report a case of MRH in a patient whose clinical presentation mimicked rheumatoid arthritis and was subsequently treated successfully with rituximab.

Multicentric Reticulohistiocytosis with Dermatomyositis-like Eruptions

A 68-year-old man presented with polyarthritis, proximal muscle weakness, and erythema of the face, arms, neck, and anterior chest that resembled the V-neck sign. Initially, dermatomyositis (DM) was considered because of the erythema, polyarthritis, and muscle weakness. He also had mediastinal and hilar lymphadenopathy on contrast-enhanced computed tomography. Unexpectedly, a biopsy of the forehead skin revealed numerous multinucleated giant cells. A biopsy of a solitary nodule on the dorsum of his right middle finger revealed similar multinucleated giant cells with ground-glass cytoplasm, leading to the diagnosis of multicentric reticulohistiocytosis (MRH). Although MRH is rare, it should be remembered that MRH can mimic DM.

Multiple myeloma masquerading as severe seropositive rheumatoid arthritis with subcutaneous nodules and mononeuritis multiplex

Multiple myeloma can rarely mimic seronegative rheumatoid arthritis (RA). We report a 55-year-old woman who presented with longstanding deforming polyarthritis with extensive subcutaneous nodules, tenosynovitis, anti-cyclic citrullinated peptide positivity and mononeuritis multiplex. Even though the clinical picture was consistent with seropositive RA, the absence of bone erosion or joint space narrowing on hand and knee radiographs led us to question the diagnosis of RA. Further investigation revealed a diagnosis of multiple myeloma with cutaneous amyloid deposits, based on serum immunofixation, bone marrow aspiration and biopsy of a subcutaneous nodule. The only clue to suspect myeloma from the basic investigations and clinical examination was mild hypercalcemia. This case serves to reiterate the need to maintain a heightened suspicion for other diagnoses even when RA appears most likely.