Lymphoproliferative disorders (LPDs) are relatively rare but serious complications in patients with rheumatoid arthritis (RA) undergoing immunosuppressive therapy. Here, we report a case of methotrexate-associated LPD (MTX-LPD) in a 74-year-old patient with RA who presented with multiple pulmonary nodules. Lung biopsy confirmed Epstein-Barr virus-positive diffuse large B-cell lymphoma. The patient had been on low-dose MTX for over 17 years. Notably, lymphocyte counts were persistently low before LPD onset and gradually improved following MTX discontinuation. Despite the spontaneous regression of LPD following MTX withdrawal and steroid therapy, a second exacerbation occurred, necessitating additional treatment. Fluctuations in lymphocyte count and C-reactive protein levels demonstrated an inverse correlation throughout the disease course. This suggests a strong association between immune reconstitution and LPD remission. We hypothesised that immunosenescence, including age-related changes in T and B-cells, may contribute to impaired immune surveillance and delayed disease resolution. Monitoring lymphocyte counts may be a useful marker for early detection and prognosis of MTX-LPD.

Granulomatosis with polyangiitis is a necrotising small vessel vasculitis characterised by granulomatous inflammation that can involve the eyes, ear-nose-throat region, and lungs, often refractory to standard immunosuppressive therapies such as glucocorticoids, rituximab, and cyclophosphamide. The complex immunopathogenesis of granulomatous lesions, involving neutrophil swarming, macrophage activation, T-cell responses, and complement activation through the C5a receptor, contributes to treatment challenges. Avacopan, an oral C5a receptor antagonist, has demonstrated efficacy in antineutrophil cytoplasmic antibody-associated vasculitis, particularly in kidney involvement, with evidence of glucocorticoid-sparing benefits from the ADVOCATE trial. However, data on its role in granulomatous manifestations remain limited. We report two cases of severe, refractory granulomatosis with polyangiitis with ocular, ear-nose-throat, and pulmonary granulomatous disease unresponsive to standard therapies but achieving complete clinical and immunological remission with avacopan. Both patients successfully discontinued glucocorticoids and showed marked clinical improvement and radiological resolution of lesions. These cases, supported by recent trial sub-analyses, suggest that avacopan may be an effective therapeutic option for granulomatous granulomatosis with polyangiitis manifestations, enabling glucocorticoid reduction and improved disease control.

Excessive production of immunoglobulin light chains can result in amyloid light-chain (AL) amyloidosis, which manifests as arthritis in approximately 3.7% of cases. Myeloma-associated amyloid arthropathy (MAA), a musculoskeletal manifestation of AL amyloidosis, often mimics rheumatoid arthritis (RA), making accurate diagnosis challenging. Musculoskeletal ultrasonography (MSKUS) has emerged as a valuable tool in the differential diagnosis of arthralgia; however, the specific sonographic features of AL amyloidosis-related arthritis remain poorly characterized. We present a case of AL amyloidosis-associated arthritis initially misdiagnosed and treated as seronegative RA. A comprehensive diagnostic workup-including MSKUS, magnetic resonance imaging, ultrasound-guided biopsy of the left shoulder joint, and systemic evaluations such as serum and urine protein electrophoresis and bone marrow examination-led to a definitive diagnosis of AL amyloidosis secondary to multiple myeloma. This case highlights the need to consider AL amyloidosis in the differential diagnosis of atypical arthritis, particularly in seronegative patients with poor response to RA therapies, involvement of non-classical joints, or systemic manifestations such as proteinuria or peripheral neuropathy. Although not diagnostic on its own, MSKUS may reveal atypical synovial changes suggestive of amyloid deposition and assist in guiding targeted biopsies, which remain essential for definitive diagnosis. Notably, this case demonstrated positive power Doppler signals, in contrast to previous reports, suggesting a broader spectrum of ultrasonographic findings in amyloid arthropathy than previously recognized.

Haematological manifestations of immunoglobulin (Ig)G4-related disease (IgG4-RD) are atypical, and few studies have addressed cytopenia in this condition. We present here a case of IgG4-RD with marked pancytopenia and splenomegaly in the absence of bone marrow abnormalities. A 67-year-old woman developed diplopia, dyspnoea, pancytopenia, and hypocomplementemia. Contrast-enhanced computed tomography showed bilateral lacrimal and submandibular gland swelling, enlargement of the cervical, mediastinal, inguinal, and para-aortic lymph nodes, splenomegaly, and granular shadows in both lungs. She had been referred to our hospital on suspicion of malignant lymphoma, but a lymph node biopsy indicated the possibility of IgG4-RD. A lacrimal gland biopsy showed infiltration of numerous lymphocytes and IgG4-positive plasma cells along with mild fibrosis. A bone marrow biopsy showed normocellular marrow with no increase in plasma cells. The IgG4-positive plasma cell count was 4 per high-power field, with an IgG4/IgG ratio of 10%. After excluding potential mimics, the diagnosis was IgG4-RD presenting with pancytopenia and splenomegaly. Prednisolone was initiated at 40mg/day, leading to the rapid normalisation of pancytopenia, recovery of complement levels, and resolution of other organ involvement such as splenomegaly. Physicians should keep in mind that IgG4-RD can present with pancytopenia and splenomegaly.

A 61-year-old Japanese woman with a 20-year-history of rheumatoid arthritis (RA) had been treated with various antirheumatic drugs including biologics and Janus kinase inhibitors. Subcutaneous methotrexate (MTX) was added to sarilumab, resulting in improvement in her joint tenderness. Six months later, however, while continuing both agents, she developed exertional dyspnea. Computed tomography revealed bilateral ground-glass opacities, and transbronchial lung cryobiopsy (TBLC) showed pathological findings consistent with MTX-induced pneumonitis. She responded rapidly to glucocorticoids, but subsequently developed recurrent episodes of RA-associated organizing pneumonia (RA-OP) despite discontinuation of MTX, which was evaluated by repeat bronchoscopy and supported the diagnosis of RA-OP, and prolonged glucocorticoid therapy was required. MTX-induced pneumonitis is a potentially life-threatening complication. This case demonstrates that subcutaneous MTX does not eliminate the risk of pneumonitis, that TBLC is a valuable diagnostic tool allowing clear pathological characterization with ample tissue to support confident pathologic diagnosis, and that the marked discrepancy in imaging supports that repeat bronchoscopy is warranted rather than avoided when new imaging points to an alternative diagnosis.

Inclusion body myositis (IBM) and immune-mediated necrotising myopathy (IMNM) are inflammatory myopathies characterized by specific clinical and pathological features. IBM is associated with human immunodeficiency virus (HIV) infection, whereas IMNM is extremely rare in individuals positive for HIV. To date, no reports have described the coexistence of IMNM and IBM-like pathological features in patients positive for HIV. Herein, we report a rare case of a 40-year-old man with HIV-associated subacute progressive myopathy presenting with simultaneous proximal and distal muscle weakness, dysphagia, and markedly elevated creatine kinase levels. Serological testing revealed strong positivity for anti-signal recognition particle antibodies. Muscle biopsy revealed coexisting pathological features suggesting both IMNM and IBM. The patient showed insufficient response to antiretroviral therapy and glucocorticoids; however, intravenous immunoglobulin therapy resulted in a marked clinical response. This case highlights the possible coexistence of IMNM and IBM-like pathology in the context of HIV infection and provides insights into the pathophysiology of HIV-associated myopathy. Furthermore, this report suggests the potential effectiveness of intravenous immunoglobulin treatment in such cases.

The diagnostic criteria for TAFRO syndrome exclude autoimmune diseases, and they have been considered to be mutually independent. However, several cases of autoimmune diseases with TAFRO signs have been reported in recent years. Also, similarities in cytokine profiles in COVID-19 and TAFRO syndrome have been previously reported. Our patient, a 53-year-old Japanese man, was diagnosed with COVID-19 and had a persistent fever. Two weeks later, pain, numbness, and oedema appeared, mainly in the right lower leg but gradually spreading to the distal extremities. Subsequently, purpura appeared on his forearms and lower legs, and 10weeks after the COVID-19 diagnosis he presented to our hospital. On admission, in addition to fever, polyangiitis, and purpura of the extremities, he had splenomegaly, lymphadenopathy, and anasarca. Skin and renal histopathology revealed fibrinoid necrotising vasculitis of small and medium-sized arteries. In addition, his platelet count was low, Alkaline phosphatase (ALP) was elevated, and there was anasarca, fever, and renal failure. A diagnosis of polyarteritis nodosa with TAFRO signs was made. On the 20th day of admission, high-dose glucocorticoids and high-dose intravenous cyclophosphamide were started. The platelet count initially improved, with gradual improvement of vasculitis and symptoms of fever, purpura, and neuropathy. However, there was another decrease in platelets, progression of renal dysfunction, and worsening of fluid retention. Tocilizumab was added, but the disease could not be controlled, and on the 51st day, necrotising fasciitis developed and the patient died. This case suggests that COVID-19, TAFRO syndrome, and vasculitis may be interrelated in their pathogeneses.

Microscopic polyangiitis (MPA) is a subtype of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), a small-vessel vasculitis that can cause organ-threatening complications. Hypertrophic pachymeningitis is a rare, central nervous system manifestation of AAV rarely involving the spine. We herein report a patient with myeloperoxidase-ANCA-positive MPA presenting with progressive cognitive decline and gait disturbance associated with communicating hydrocephalus secondary to spinal hypertrophic pachymeningitis. The patient responded well to high-dose prednisolone and rituximab and showed significant clinical and radiological improvement without surgery. The present case not only demonstrated that spinal hypertrophic pachymeningitis in AAV can cause reversible dementia associated with communicating hydrocephalus but also highlighted the potential of timely immunosuppressive therapy to induce remission.

A 46-year-old man was diagnosed with anti jo-1 antibody-positive dermatomyositis 11years ago and had been treated with prednisolone and tacrolimus. In the present case, after contracting SARS-CoV-2 virus infection, his dyspnoea rapidly worsened, and he presented with renal and cardiac failure. Based on the biopsy results of the same area and anti-U1-RNP antibody positivity, he was diagnosed with systemic sclerosis and scleroderma renal crisis and required haemodialysis. A renal biopsy performed later showed tubular atrophy, intratubular cell debris, and endothelial cell damage, consistent with scleroderma renal crisis. Although rapid skin hardening and high-dose glucocorticoid use are known risks for scleroderma renal crisis, scleroderma renal crisis triggered by novel SARS-CoV-2 virus infection has never been reported before and is very rare. It is crucial to identify the relationship between the scleroderma renal crisis and SARS-CoV-2 virus infection. This relationship can be explained through the RAS system, which is believed to play a role in the development of both.

Granulomatosis with polyangiitis (GPA) is a rare autoimmune vasculitis primarily affecting the respiratory tract and kidneys. This case report describes a severe and atypical presentation of GPA in a 42-year-old male, who initially presented with sudden onset of cough, myalgia, dysaesthesia, and lower limb oedema. Initial tests indicated elevated inflammatory markers and white blood cell count. Subsequent imaging revealed a suspicious pulmonary nodule, but the patient experienced a syncopal episode and myocardial infarction before scheduled surgery. Despite normal myocardial biopsy results and negative bacterial/viral tests, the patient developed ischaemic symptoms in the lower extremities, leading to severe limb ischaemia and amputation of the left distal third thigh. Few days later he developed renal involvement with proteinuria, haematuria, active urinary sediment, and rapidly progressive renal dysfunction. The clinical scenario and the detection of high-titre antineutrophil cytoplasmatic antibodies (ANCA) were highly suggestive for GPA; despite the lack of histological confirmation due to mandatory anticoagulant treatment for the recent myocardial event, treatment with methylprednisolone and rituximab was started and led to rapid clinical improvement. Subsequently histological analysis of the amputated leg confirmed necrotising vasculitis. This case highlights the importance of considering GPA in differential diagnoses involving multiorgan symptoms and underscores the complexities in diagnosing and managing this rare condition, especially when typical diagnostic biopsies are not feasible.