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

Table 1 Comparison of multicentric reticulohistiocytosis and rheumatoid arthritis

	MRH	RA
Joint involvement	Hand joint, knee joint, the shoulder, elbow, hip, ankle, and metatarsophalangeal joint	Double hand joint, wrist joint, foot joint, etc.
	The distal interphalangeal joints involvement is frequent	The distal interphalangeal joints involvement is rare
Rate of joint destruction	Rapid	Slow
Radiologic characteristics	Enlargement of joint cavity	Periarticular osteopenia
	Loss of articular cartilage and resorption of subchondral bone; no bone loss and abnormal new bone formation	Narrowing of the joint space, and bone erosion

MRH: Multicentric reticulohistiocytosis; RA: Rheumatoid arthritis; DIP: Distal interphalangeal; PIP: Proximal interphalangeal joint; MCP: Metacarpophalangeal joints.

Table 2 Comparison of multicentric reticulohistiocytosis and dermatomyositis

	DM	MRH
Amyasthenia	More than 90% showed a symmetrical proximal muscle weakness	Rare
Increased myoenzyme	Almost all patients with DM (except CADM) have at least one myoenzyme level at some point in the disease course	Rare
Skin manifestations	Gottron papules and heliotrope rash are the definitive features of DM; Gottron signs, erythema along the light site, heterochromia, nail fold changes, scalp involvement, and skin calcification are also typical manifestations of DM	The manifestations of skin lesions include popular nodules and macules. Skin lesions are primarily distributed on the face, scalp, behind the ears, neck, anterior chest, back, waist, and abdomen, arms, hands, and thigh
Skin biopsy	The sporadic or focal infiltration of lymphocytes, plasma cells, and histiocytes	A large number of histiocytes and multinucleated giant cells with an eosinophilic cytoplasm and hairy glass-like changes

MRH: Multicentric reticulohistiocytosis; DM: Dermatomyositis; CADM: Clinically amyopathic dermatomyositis.

Table 3 The clinical characteristics of multicentric reticulohistiocytosis

Clinical manifestation
Skin lesions	The skin is the most frequently involved site of MRH. Skin lesions may be the first symptom and are primarily distributed on the face, scalp, behind the ears, neck, anterior chest, back, waist, and abdomen, arms, hands, and thigh. The manifestations of skin lesions include papular nodules, and macules. MRH can also involve mucous membranes (e.g., oral mucosa, gingival mucosa, and laryngeal mucosa)
MRH-associated arthritis	Arthritis can appear as the first symptom of MRH and also can occur simultaneously with skin lesions. MRH-associated arthritis can be characterized as diffuse, symmetric, progressive, and destructive. MRH is most commonly involved in the hand joints, especially the distal interphalangeal joint, followed by the knee joint, the shoulder, elbow, hip, ankle, and metatarsophalangeal joint. The affected joints exhibit swelling, pain, increase in skin temperature, joint effusion, and some patients can also experience morning stiffness
Other clinical manifestations	Muscle involvement: Myalgia or decreased muscle strength; Electromyography (EMG) may exhibit myogenic lesions in some patients; Lung involvement: Dyspnea, pulmonary nodules, pleural effusion, or pulmonary interstitial fibrosis; Heart involvement: Pericardial effusion and myocarditis; Laryngeal involvement: Hoarseness, foreign body sensation in the larynx, or laryngeal abnormalities; Thyroid involvement: Hypothyroidism; Thrombosis has also been reported in patients with MRH. A small number of patients have extensive systemic involvement of the larynx, lungs, spleen, and plasma membranes at the same time. Systemic symptoms: Fatigue, fever, and weight loss
Laboratory tests
Non-specific. Some patients may have increased leukocytes, decreased hemoglobin, accelerated sedimentation, and elevated lipids
Histopathology
Histopathological manifestations: a large number of histiocytes and multinucleated giant cells with an eosinophilic cytoplasm and hairy glass-like changes
Immunohistochemistry: macrophage marker CD68 is positive; the Langerhans cell tissue markers S-100, CD1a and B cell markers CD19 and CD20 are negative; CD45, CD43, Mac387, and lysozyme are positive to varying degrees
MRH-associated diseases
Systemic autoimmune diseases: systemic lupus erythematosus, rheumatoid arthritis, Sjogren's syndrome, dermatomyositis, hypothyroidism, diabetes, and tuberculosis
Malignancy: Covering almost all solid tumors and hematologic malignant diseases
Differential diagnosis
MRH is most easily confused with rheumatoid arthritis, dermatomyositis, and psoriatic arthritis
Treatment
Initial treatment: Glucocorticoids combined with immunosuppressants regimens. Commonly used immunosuppressants include methotrexate, cyclophosphamide, hydroxychloroquine, and leflunomide
Biological agents: TNF-α antagonists (e.g., etanercept, adalimumab, and infliximab), IL-6 receptor antagonists (tocilizumab), and IL-1 receptor antagonists (anakinra)
Prognosis
The prognosis of MRH patients varies greatly among individuals; It is related to treatment choice, response to drug therapy, and comorbidities

MRH: Multicentric reticulohistiocytosis; TNF-α: Tumor necrosis factor-α; IL: Interleukin.