TEMPI syndrome: A clinical, light-microscopic and phenotypic evaluation with review of the literature

BACKGROUND AND OBJECTIVES

TEMPI (telangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonaryshunting) syndrome is a rare multisystemic disease classified as a monoclonal gammopathy of cutaneous significance. The pathogenesis and etiology of TEMPIare not well known because of the rarity of this disorder. Although telangiectasias are the hallmark of this syndrome, skin biopsies are rarely performed. We aim to further characterize TEMPI syndrome through the evaluationof a skin biopsy.

METHODS

We reviewed the histopathology and immunophenotypic profile of a skin biopsy from a 53-year-oldwoman diagnosed with TEMPI syndrome. Other components of her syndromic complex included an IgA myeloma, elevated vascular endothelial growth factor (VEGF), and erythrocytosis.

RESULTS

A biopsy showed prominent vascular ectasia with some degree of microvascular basement membranezone thickening. Our patient had a reduction in neoplastic plasma cell burdenand clearing of her telangiectasias following myeloma directed treatment.

CONCLUSIONS

TEMPI can beviewed as a reactive vascular paraneoplastic syndrome in the setting of a plasma cell dyscrasia. Elaboration of VEGF from neoplastic plasma cells is likely pathogenetically implicated and appears to be a common link that explains other vascular lesions associated with monoclonal gammopathy syndromes.

Multiparametric Flow Cytometry in the Evaluation of Plasma Cell Proliferative Disorders: Current Paradigms for Clinical Practice

Diagnosis of plasma cell proliferative disorders (PCPDs) is primarily based on the demonstration of monoclonal protein (M-Protein) in blood and/ or urine which often precedes clinical manifestations of the disease. The basic pathophysiology behind the M-protein presence is the proliferation of clonal plasma cells (PCs) in bone marrow or extramedullary sites and is assessed using cytomorphology and immunophenotyping. The role of multiparametric flow cytometry (MFC) for PC identification is technically the most valuable tool in this context as it characterizes as well as quantifies the clonal PCs based on differential expression of various immunophenotypic (IPT) markers. From a diagnostic perspective, MFC is critical in the definite identification of the clonal PCs and delineates benign and borderline entities at one end of the spectrum (MGUS, SMM) with lower clonal PC% and, malignant diseases at the other end (MM and PCL) with higher clonal PC fraction. The role of MFC in assessment of measurable residual disease (MRD) and monitoring of progression in MM and various PCPDs has been validated in multiple clinical studies and is probably one of the most promising tools for predicting treatment outcomes. Furthermore, MFC also plays a crucial role in disease prognostication based on specific IPT profiles. An additional role of MFC in the current clinical scenario is the evaluation of tumor microenvironment based on immune cell repertoire, which is reflecting encouraging results across. Thus, in the current review we concisely describe the role of MFC as a reliable and essential modality in PCPDs, from diagnosis to prediction of treatment outcome and disease monitoring.

From Multiple Myeloma to Acute Myeloid Leukemia: A Case Report of a 61-year-old Woman after 8 Years of Chemotherapy and Immunotherapy

BACKGROUND

As the second most prevalent hematologic malignancy, multiple myeloma (MM) affects plasma cells and is characterized by chromosomal abnormalities, particularly involving the immunoglobulin heavy chain switch region. MM represents a biologically and clinically heterogeneous hematological malignancy that serves as a clonal evolution model, exhibiting clonal heterogeneity throughout all stages from monoclonal gammopathy undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to MM. Although significant progress has been made in the treatment of MM, leading to improved patient outcomes, concerns are arising regarding disease relapse due to the presence and selection of pre-existing resistant clones or selective pressure during therapy.

CASE PRESENTATION

We present a case of multiple myeloma (MM) in a female patient, who underwent an 8-year course of treatment, including chemotherapy, immunomodulators, hematopoietic stem cell transplantation, CD38 monoclonal antibody, and chimeric antigen receptor T-cell (CAR-T), and was recently diagnosed with concurrent progressive MM and acute myeloid leukemia (AML). This patient has witnessed the evolution of MM treatment paradigms.

CONCLUSION

In this course, disease relapses occurred twice, one of which was manifested by a light chain escape (LCE). Moreover, through the course of the disease in this patient, we review the process of clonal evolution that may be relevant.

Single monoclonal spike characterized as double monoclonal gammopathy in a patient with multiple myeloma: A rare finding

Multiple myeloma (MM) is associated with the secretion of a unique monoclonal protein (M-protein) due to overproduction of immunoglobulin (Ig) by a clone of abnormally proliferating plasma cells. However, in 4% of the cases more than one M-protein can be found. This category of gammopathies is called "double monoclonal gammopathies." Here, we present a rare case of MM with double monoclonal gammopathy, where the presence of both M-proteins was observed in the single sharp peak on capillary zone electrophoresis (CZE). Further the interference of Hook effect is also discussed. Double monoclonal gammopathies need to be identified to increase diagnostic accuracy and reliability, and to get a better understanding of the disease pathogenesis and progression.

Therapy of necrobiotic xanthogranuloma - case series and review of the literature

Necrobiotic xanthogranuloma is a rare disease that is part of the non-Langerhans cell histiocytoses. It is characterized by yellowish skin lesions, which are typically periorbitally localized. Extracutaneous manifestations of all organs are possible and can cause potentially life-threatening complications. The disease also belongs to the facultative paraneoplasias and is often associated with paraproteinemia. These aspects should be considered regarding further diagnostics. Due to the rarity of the disease, there are no standardized guidelines for therapy so far. The combination of prednisolone and chlorambucil as well as intravenous immunoglobulins seem to be effective therapeutic options. We present four cases from our clinic as well as the current results of the literature in this mini-review and would like to highlight the therapeutic challenge as well as the need for the development of guidelines.

Non-crystalline light chain proximal tubulopathy, a morphologically protean entity

BACKGROUND

Light chain proximal tubulopathy (LCPT) is a rare form of paraprotein-related disease, occurring in two main histopathological forms: crystalline and non-crystalline. The clinicopathological features, treatment strategies and outcomes, especially of the non-crystalline form, are not well described.

METHODS

We conducted a single-centre retrospective case series of 12 LCPT patients, 5 crystalline and 7 non-crystalline, between 2005 and 2021.

RESULTS

The median age was 69.5 years (range 47-80). Ten patients presented with CKD and significant proteinuria (median estimated glomerular filtration rate of 43.5 ml/min/1.73 m2; urine protein:creatinine ratio 328 mg/mmol). Only six patients had known haematological disease at the time of renal biopsy. Multiple myeloma (MM) was diagnosed in seven patients cases and monoclonal gammopathy of renal significance (MGRS) in five patients. A clone was detected in all cases combining serum/urine electrophoresis and free light chain (LC) assays. Crystalline and non-crystalline variants had similar clinical presentations. For the non-crystalline variant, a diagnosis was reached based on a combination of CKD without another cause, haematological workup, LC restriction on immunofluorescence and abnormalities on electron microscopy (EM). Nine of 12 patients received clone-directed treatment. Patients who achieved haematological response (including all non-crystalline LCPT) had improved renal outcomes over a median follow-up of 79 months.

CONCLUSIONS

The non-crystalline variant may go unrecognised because of its subtle histopathological features and requires EM to distinguish it from 'excessive LC resorption without tubular injury'. Clone-directed treatment with good haematological response improves renal outcomes in both variants but limited data exist in MGRS. Multicentre prospective studies are needed to better define the clinicopathological characteristics associated with poor outcomes and optimize treatment strategies in patients with MGRS.

Comprehensive Next-Generation Sequencing Testing in a Patient with TEMPI Syndrome

TEMPI syndrome is a new and poorly understood disease that is currently considered a type of plasma cell neoplasm with paraneoplastic manifestations. The TEMPI acronym defines the hallmarks of the syndrome: T for telangiectasia; E for erythrocytosis with elevated erythropoietin; M, monoclonal gammopathy; P, perinephric collections; and I, intrapulmonary shunting. Due to the marked erythrocytosis as the most common presenting feature, TEMPI is often misdiagnosed as polycythemia vera. However, unlike polycythemia vera, TEMPI is not associated with a JAK2 mutation. The pathogenesis of TEMPI syndrome is unknown, although a few hypothetical disease mechanisms have been previously discussed. Here we present a new case of TEMPI syndrome, discuss results of a next-generation sequencing (NGS) panel covering 1,425 known cancer-related genes, and review the current literature with focus on an update of the genetics of TEMPI syndrome. This is the first report of TEMPI that includes results of comprehensive NGS testing.

Monoclonal gammopathy of renal significance: Multidisciplinary approach to diagnosis and treatment

Monoclonal gammopathy of renal significance (MGRS) is a hemato-nephrological term referring to a heterogeneous group of kidney disorders characterized by direct or indirect kidney injury caused by a monoclonal immunoglobulin (MIg) produced by a B cell or plasma cell clone that does not meet current hematologic criteria for therapy. MGRS-associated kidney diseases are diverse and can result in the development of end stage kidney disease (ESKD). The diagnosis is typically made by nephrologists through a kidney biopsy. Many distinct pathologies have been identified and they are classified based on the site or composition of the deposited Mig, or according to histological and ultrastructural findings. Therapy is directed towards the identified underlying clonal population and treatment decisions should be coordinated between hematologists and nephrologists in a multidisciplinary fashion, depend on the type of MGRS, the degree of kidney function impairment and the risk of progression to ESKD.

Light Chain Deposition Disease Recurrence in Renal Allograft after Long-Term Remission

Light chain deposition disease (LCDD) is a rare manifestation of monoclonal gammopathy, which can lead to renal failure. We previously reported a detailed recurrence process in a case of LCDD after renal transplantation. To the best of our knowledge, no report has described the long-term clinical course and renal pathology findings of recurrent LCDD in patients after renal transplantation. In this case report, we describe the long-term clinical presentation and changes in renal pathology of the same patient after early LCDD relapse in a renal allograft. A 54-year-old woman with recurrent immunoglobulin A λ-type LCDD in an allograft was admitted 1 year post-transplant for bortezomib and dexamethasone therapy. At 2 years post-transplantation, a graft biopsy performed after complete remission was achieved, showing some glomeruli with residual nodular lesions similar to the pre-treatment renal biopsy findings. However, the enlarged subendothelial space disappeared. She remained in complete remission serologically for 6 years. Subsequently, the ratio of serum κ/λ-free light chains decreased gradually. She underwent a transplant biopsy approximately 12 years after renal transplantation due to increased proteinuria and decreased renal function. Compared with the previous graft biopsy, almost all glomeruli showed advanced nodule formation and subendothelial expansion. Because the LCDD case relapsed after long-term remission following renal transplantation, protocol biopsy monitoring might be necessary.

Prevalence, mutational spectrum and clinical implications of clonal hematopoiesis of indeterminate potential in plasma cell dyscrasias

Clonal hematopoiesis of indeterminate potential (CHIP) is common both in healthy individuals and patients with hematological cancers. Recent studies have showed worse prognosis for patients with multiple myeloma (MM) and non-Hodgkin lymphoma undergoing stem cell transplant, that have concomitant presence of CHIP. Data regarding the clinical and biological role of CHIP in plasma cell dyscrasias (PCDs) is rapidly increasing. However, the prevalence and prognostic implication of CHIP in patients with MM outside of the transplant setting, and in those with other more indolent PCDs remains elusive. Here we explored the prevalence and clinical implications of CHIP detected through next-generation sequencing in 209 patients with PCDs including MM, light chain (AL) amyloidosis (ALA), monoclonal gammopathy of undetermined significance (MGUS), and smoldering multiple myeloma (SMM). To avoid attributing the mutations to the plasma cell clone, CHIP was defined as the presence of DNMT3A, TET2, or ASXL1 mutations in the peripheral blood or bone marrow (DTA-CH). The prevalence of DTA-CH was 19% in patients with PCDs, with no difference between each PCD. TET2 (23%) and DNMT3A (22%), were the most frequently mutated genes. DTA-CH correlated with older age in MM (P = .001) and MGUS/SMM (P = 0.0007), as well as with coronary artery disease or congestive heart failure in MM (P = .03). DTA-CH did not predict worse OS or PFS in either MM or ALA, nor it predict higher risk of progression to MM in patients with MGUS/SMM. Our results overall further elucidate the prevalence and mutational spectrum of CHIP in PCDs, providing more information regarding the clinical relevance of CHIP in this patient population.

TEMPI Syndrome: Update on Clinical Features, Management, and Pathogenesis

TEMPI (telangiectasias, elevated erythropoietin level and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonary shunting) syndrome is a rare and newly defined multisystemic disease, which belongs to "monoclonal gammopathy of clinical significances". Due to its rarity, the etiology, pathogenesis, and clinical features of this disease remain largely unknown. Owing to its hidden and diverse clinical manifestations, missed diagnosis and misdiagnosis are common. In recent years, as more patients (including three fatal cases) were identified, some special clinical manifestations other than the typical pentad of TEMPI syndrome have been reported. Meanwhile, several studies attempting to identify the pathogenesis of TEMPI syndrome were conducted. In this review, we summarize the reported clinical characteristics of TEMPI syndrome and discuss the current and potential treatment options for patients with TEMPI syndrome, including those with relapsed/refractory disease. Furthermore, we provide an overview of current knowledge on the pathophysiology of TEMPI syndrome.

[Renal involvement in monoclonal gammopathies]

INTRODUCTION

The kidney is one of the organs most frequently affected by disease processes which produce monoclonal immunoglobins, therefore renal morphological and immunopathological alterations should be clearly recognized.

OBJECTIVE

To describe the pathological features of renal involvement in monoclonal gammopathies.

MATERIAL AND METHODS

A descriptive, retrospective and cross-sectional study of renal biopsies studied in a single center during a period of 14 years was carried out.

RESULTS

102 cases were included, of which 53% were male patients and the median age was 62.5 years (range 34 - 79). 97% of the biopsies were from native kidneys. The most frequent histopathological diagnosis (31.4%) was myeloma kidney, with kappa being the light chain most frequently deposited (65.6% of cases). AL amyloidosis was the second most common (29.4%) where the lambda chain predominated in 86.6%, followed by light chain deposition disease (20.6%) with the predominance of the kappa chain in 66.6%.

CONCLUSIONS

The most frequent renal involvement due to monoclonal gammopathies was myeloma kidney with deposition of kappa light chains, followed by AL lambda amyloidosis; these diseases were found more frequently in patients over 50 years of age.

Reviewing the Significance of Vitamin D Substitution in Monoclonal Gammopathies

Vitamin D is a steroid hormone that is essential for bone mineral metabolism and it has several other effects in the body, including anti-cancer actions. Vitamin D causes a reduction in cell growth by interrupting the cell cycle. Moreover, the active form of vitamin D, i.e., 1,25-dihydroxyvitamin D, exerts various effects via its interaction with the vitamin D receptor on the innate and adaptive immune system, which could be relevant in the onset of tumors. Multiple myeloma is a treatable but incurable malignancy characterized by the growth of clonal plasma cells in protective niches in the bone marrow. In patients affected by multiple myeloma, vitamin D deficiency is commonly correlated with an advanced stage of the disease, greater risk of progression, the development of pathological fractures, and a worse prognosis. Changes in the vitamin D receptor often contribute to the occurrence and progress of deficiencies, which can be overcome by supplementation with vitamin D or analogues. However, in spite of the findings available in the literature, there is no clear standard of care and clinical practice varies. Further research is needed to better understand how vitamin D influences outcomes in patients with monoclonal gammopathies.

A patient with Gaucher disease and plasma cell dyscrasia: bidirectional impact

Patients with Gaucher disease (GD), a rare autosomal recessive glycosphingolipid storage disease, commonly present to hematologists with unexplained splenomegaly, thrombocytopenia, anemia, and bone symptoms. Patients with GD may develop other manifestations, such as autoimmune thrombocytopenia, monoclonal gammopathy, multiple myeloma, or, even more rarely, other hematological malignancies; sometimes they are first diagnosed during an assessment of those disorders. Although the diagnosis and management of patients with GD have significantly evolved over the last 30 years, some patients remain poor responders to GD-specific therapy, needing novel and investigational therapies. Ideally, patients with GD, like patients with other rare diseases, should be managed by a multidisciplinary team expert with the diverse clinical manifestations and potential GD-related or -unrelated comorbidities. The hematology community should be knowledgeable regarding the presentation and the variety of hematologic complications and comorbidities associated with Gaucher disease.

Monoclonal gammopathies of clinical significance

"Monoclonal gammopathy of clinical significance" (MGCS) is the term used to describe nonmalignant monoclonal gammopathies causing important disease. MGCS is the differential diagnosis for any patient presenting with what appears to be a monoclonal gammopathy of undetermined significance but is also experiencing other unexplained symptoms. Broadly, these conditions can be separated into symptoms and signs referable to the nerves, the kidneys, and the skin. The first step in making these diagnoses is to consider them. With a particular condition in mind, the next step is to order those tests that can help confirm or dismiss a particular diagnosis. Nearly all of the renal and dermatologic conditions are diagnosed by renal and skin biopsies, respectively. The importance of a highly competent renal pathologist and dermatopathologist cannot be underestimated. Biopsy is less specific for the neuropathic conditions. Because several of the MGCSs are syndromes, recognizing other manifestations is also key. Treatment recommendations for many of these conditions are anecdotal because of their rarity, but for several of the conditions, IV immunoglobulin, rituximab, and plasma cell-directed therapy are the best options.

Characterization of circulating myeloma tumor cells by next generation flowcytometry in scleromyxedema patient: a case report

INTRODUCTION

Scleromyxedema (rare cutaneous mucinosis), is characterized by the formation of lichenoid papules and presence of Serum monoclonal IgG in most cases, or all; after repeated testing.

PATIENT CONCERNS

The patient is a 51-year-old male presented with thick, disfiguring elephant-like erythematous skin folds over the forehead, papular shiny eruptions over ears and trunk and waxy erythematous papules over arms and hands without dysphagia or respiratory or neurologic symptoms DIAGNOSIS: : Skin biopsy from right arm was consistent with scleromyxedema. Serum cryoglobulin was reported negative. Complete blood count and routine blood biochemistry were normal. Thyroid function tests were normal. Serum protein electrophoresis and immunofixation showed monoclonal band of 14.5 g/L typed as IgG lambda.

INTERVENTIONS

Our patient was refractory to lenalidomide however improved clinically on immunoglobulins infusions on monthly basis without change in the MGUS level.

OUTCOMES

NGF analysis revealed approximately 0.25% Lambda monotypic plasma cells in the bone marrow expressing CD38, CD138, and CD27 with aberrant expression of CD56 and were negative for CD45, CD19, CD117, and CD81. We also detected 0.002% circulating plasma cells (PCs) in peripheral blood.

CONCLUSION

The immunophenotype of circulating tumor cells (CTCs) remain close to the malignant PCs phenotype in the BM. Hence, we report NGF approach as a novel diagnostic tool for highly sensitive MRD detection in plasma cell dyscrasias including scleromyxedema.

Monoclonal gammopathy with significance: case series and literature review

Monoclonal gammopathy of undetermined significance (MGUS) is considered an asymptomatic precursor of malignant lymphoid disorders. This case series and literature review shows that these monoclonal gammopathies can cause significant morbidity. We describe a patient with angioedema due to acquired C1-esterase inhibitor deficiency, a patient with cryoglobulinemia type II causing skin vasculitis and glomerulonephritis, and a patient with glomerulonephritis and nephrotic syndrome - all caused by a monoclonal gammopathy that can be classified as MGUS. Clinicians should be familiar with these consequences of monoclonal gammopathies. The term MGUS should only be used in patients without organ damage caused by monoclonal gammopathies.

Monoclonal Gammopathy of Renal Significance and its Associated Experimental Models

Monoclonal gammopathy of renal significance (MGRS) is a state of circulating monoclonal immunoglobulin (Ig) and light chains that cause kidney injury without definite evidence of multiple myeloma (MM). Although chemotherapy is used to treat many variants of MGRS and has been recently recommended, relatively limited clinical validation studies are available. A few transgenic models of MM reveal renal deposition of monoclonal Ig and light chains. We have demonstrated that the XBP1s-transgenic mouse model from early plasma cell dyscrasia to MM reveals monoclonal IgG/kappa deposition at the subendothelial spaces of the glomeruli, mimicking proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Inhibition of a key immune-modulator, gp96/grp94, genetically or pharmacologically results in a significant reduction of plasma cells within the bone marrow and reduced renal deposition of monoclonal IgG and kappa light chain. This article will review the emerging role of in vitro and animal models from plasma cell dyscrasia to MM in understanding the renal deposition of monoclonal Ig and light chains, along with its potential treatment strategies.

Multiparameter Flow Cytometry Identification of Neoplastic Subclones: A New Biomarker in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Multiparameter flow cytometry (MFC)-based clonality assessment is a powerful method of diagnosis and follow-up in monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). However, the relevance of intraclonal heterogeneity in immunophenotypic studies remains poorly understood. The main objective of this work was to characterize the different immunophenotypic subclones in MGUS and MM patients and to investigate their correlation with disease stages. An 8-color MFC protocol with 17 markers was used to identify the subclones within the neoplastic compartment of 56 MGUS subjects, 151 newly diagnosed MM patients, 30 MM subjects in complete remission with detectable minimal residual disease, and 36 relapsed/refractory MM patients. Two or more clusters were observed in > 85% of MGUS subjects, 75% of stage I MM patients, and < 15% in stage III. Likewise, a significant correlation between the dominant subclone size, secondary cytogenetic features, and changes in the expression of CD27, CD44, and CD81 was detected. The loss of intraclonal equilibrium may be an important factor related with kinetics and risk of progression not well considered to date in MFC studies. The MFC strategy used in this work can provide useful biomarkers in MGUS and MM.

IL-10 inducible CD8+ regulatory T-cells are enriched in patients with multiple myeloma and impact the generation of antigen-specific T-cells

Tumor-mediated immunosuppression via regulatory T-cells is a key player among the various immune-escape mechanisms in multiple myeloma. We analyzed the generation, distribution, function and immunophenotype of CD8+CD28- regulatory T-cells in patients with multiple myeloma. Functionality of CD8+CD28- T-cells was assessed by immunological assays using ex vivo generated antigen-specific T-cells from patients with plasma cell dyscrasias and healthy donors. Detailed analysis of distribution, immunophenotype and cytotoxic potential of CD8+CD28- T-cells was performed by flow cytometry and ELISA. We found that the amount of CD8+CD28- T-cells was directly correlated with the suppression of antigen-specific T-cell responses in patients with plasma cell dyscrasia. Analyzing the CD8+CD28- T-cells in detail, increased numbers of these cells were observed in the bone marrow (i.e., tumor microenvironment) of patients with plasma cell dyscrasia. Furthermore, we identified the expression of lymphocyte function-associated antigen 1 (LFA-1) as a marker of immunosuppression and defined the CD8+CD28-CD57+LFA-1high population as the relevant immunosuppressive compartment. These regulatory T-cells act as immunosuppressors via soluble factors and incubation with IL-10 augmented their immunosuppressive capacity. The immunosuppressive regulatory network of IL-10 and the CD8+CD28-CD57+LFA-1high regulatory T-cells show unique characteristics and contribute to the tumor immune escape mechanism in patients with multiple myeloma.

Acquired Fanconi syndrome secondary to light chain deposition disease associated with monoclonal gammopathy of renal significance: A case report

RATIONALE

Renal Fanconi syndrome (FS) is a rare complication of monoclonal gammopathy. It is characterized by the impairment of renal proximal tubular function leading to normoglycemic glycosuria, aminoaciduria, hypophosphatemia, hypouricemia and proximal renal tubular acidosis. Renal impairment in monoclonal gammopathy, without fulfilling the criteria of multiple myeloma, is categorized as monoclonal gammopathy of renal significance (MGRS).

PATIENT CONCERNS

A 54-year-old male presented with progressively aggravated bone pain and limitation of activity was admitted to our department. A proximal renal tubular damage was suggested by hypophosphatemia, compensated metabolic acidosis, renal glycosuria, aminoaciduria, and hypouricemia. M-protein of IgA kappa was detected by immunofixation electrophoresis. Mildly increased plasma cells were found in bone marrow cytomorphologic examination. Renal biopsy revealed diffuse linear monoclonal IgA-kappa light chain deposits along tubular basement membranes (TBMs), while lambda was negative. Electron microscopy showed granular electron-dense deposits along the outer aspect of TBMs.

DIAGNOSES

The patient was diagnosed as FS induced osteomalacia secondary to monoclonal gammopathy of renal significance (MGRS) (IgA-κ type) and LCDD.

INTERVENTIONS

He was treated with bortezomib, supplementation by phosphate, alkali agents, and active vitamin D. He responded well to the treatment symptomatically.

OUTCOMES

We reported a rare case of adult acquired FS with hypophosphatemic osteomalacia secondary to LCDD associated with MGRS and the patient was successfully treated with bortezomib.

LESSONS

Although few cases of LCDD with isolated symptoms of tubulointerstitial nephropathy, rather than glomerular symptoms have been reported. It still needs to be recognized as a differential diagnosis in monoclonal gammopathy.

TEMPI Syndrome: Erythrocytosis in Plasma Cell Dyscrasia

TEMPI (telangiectasias, erythrocytosis with elevated erythropoietin, monoclonal gammopathy, perinephric fluid collections, intrapulmonary shunting) syndrome is a newly described clinical entity that is generally considered a plasma cell dyscrasia with multiple system involvement. The etiology and pathophysiology of this condition remains elusive. Nevertheless, clonal plasma cells and monoclonal protein appear to be major contributors. The early diagnosis of TEMPI syndrome is essential because therapies targeting the underlying plasma cells can lead to a dramatic response. Bortezomib-based chemotherapy, daratumumab monotherapy, and autologous hematopoietic stem cell transplantation can result in reversal of most manifestations. Nevertheless, the diagnosis of TEMPI syndrome remains a substantial challenge owing to its rarity and the complexity of clinical presentations. TEMPI syndrome is often misdiagnosed as other causes of erythrocytosis, resulting in a delayed diagnosis and further clinical deterioration. The aim of the present review was to present the clinical and biologic features of TEMPI syndrome, highlighting the differential diagnosis and outlining the present understanding of its pathophysiology and treatment.

C3 glomerulopathy associated with monoclonal Ig is a distinct subtype

Monoclonal immunoglobulins (MIg) may play a causal role in C3 glomerulopathy (C3G) by impairing regulation of the alternative pathway of complement. Ninety-five patients with C3G were tested for MIg of which 36 were positive. Their mean age at diagnosis was 60 years and among patient 50 years and older, 65.1% had a MIg. At presentation, median serum creatinine and proteinuria were 1.9 mg/dL and 3.0 g/24 hours. Hematuria was present in 32 (88.9%) patients. Twelve (34.3%) patients had low C3 levels. C3 nephritic factor was detected in 45.8% patients; pathogenic variants in complement protein genes were rare. Hematologic evaluation revealed monoclonal gammopathy of renal significance in 26 patients, multiple myeloma in five, smoldering multiple myeloma in two, and chronic lymphocytic leukemia, lymphoma, or type I cryoglobulin each in one patient. After a median follow-up of 43.6 months, the median serum creatinine and proteinuria were 1.4 mg/dL and 0.8g/24 hours. Nine patients developed ESRD. Sixteen patients received MIg-targeted treatment, 17 patients received non-targeted treatment while three patients were managed conservatively. Of the 16 patients receiving MIg-targeted treatment, ten achieved complete/very good/partial hematologic response. Of these, seven achieved a complete/partial/stable renal response. Five patients receiving targeted treatment did not achieve hematologic response, none had a renal response. Patients receiving targeted treatment were more likely to have multiple myeloma/smoldering multiple myeloma. Patients receiving non-targeted treatment were more likely to have monoclonal gammopathy of renal significance. Thus, C3G with MIg is seen in older patients, C3 nephritic factor is the most common autoantibody detected, and MIg-targeted treatment may result in remission and stabilization of kidney function in a subset of these patients.

Lymphoma-like monoclonal B cell lymphocytosis in a patient population: biology, natural evolution, and differences from CLL-like clones

High-count monoclonal B cell lymphocytosis (MBL) with a chronic lymphocytic leukemia (CLL) phenotype is a well-known entity, featuring 1-4% annual risk of progression towards CLL requiring treatment. Lymphoma-like MBL (L-MBL), on the other hand, remains poorly defined and data regarding outcome are lacking. We retrospectively evaluated 33 L-MBL cases within our hospital population and compared them to 95 subjects with CLL-like MBL (C-MBL). Diagnoses of L-MBL were based on asymptomatic B cell clones with Matutes score < 3, B cells < 5.0 × 10³/μl, and negative computerized tomography scans. We found that median B cell counts were considerably lower compared to C-MBL (0.6 vs 2.3 × 10³/μl) and remained stable over time. Based on immunophenotyping and immunogenetic profiling, most L-MBL clones did not correspond to known lymphoma entities. A strikingly high occurrence of paraproteinemia (48%), hypogammaglobulinemia (45%), and biclonality (21%) was seen; these incidences being significantly higher than in C-MBL (17, 21, and 5%, respectively). Unrelated monoclonal gammopathy of undetermined significance was a frequent feature, as the light chain type of 5/12 paraproteins detected was different from the clonal surface immunoglobulin. After 46-month median follow-up, 2/24 patients (8%) had progressed towards indolent lymphoma requiring no treatment. In contrast, 41% of C-MBL cases evolved to CLL and 17% required treatment. We conclude that clinical L-MBL is characterized by pronounced immune dysregulation and very slow or absent progression, clearly separating it from its CLL-like counterpart.

Primary systemic amyloidosis with skin and cardiac involvement: a case report

Primary systemic amyloidosis is characterized by the deposition of insoluble monoclonal immunoglobulin light chains in various tissues and is usually associated with an underlying plasma cell dyscrasia. In the early stage of the disease, dermatological findings can be the only manifestation, as opposed to organ involvement in the later stages. A dermatologist can diagnose amyloidosis early with a skin biopsy stained with Congo red dye and other appropriate investigations. This case report describes a female patient with primary systemic amyloidosis confirmed histologically from a skin biopsy. When the diagnosis was established, cardiac involvement and monoclonal gammopathy were already present. Treatment with bortezomib and dexamethasone was initiated; due to side effects, the treatment was later switched to lenalidomide, which was better tolerated.

How I manage monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of undetermined significance (MGUS) is, in many ways, a unique hematologic entity. Unlike most hematologic conditions in which the diagnosis is intentional and credited to hematologists, the discovery of MGUS is most often incidental and made by nonhematologists. MGUS is considered an obligate precursor to several lymphoplasmacytic malignancies, including immunoglobulin light-chain amyloidosis, multiple myeloma, and Waldenström macroglobulinemia. Therefore, long-term follow-up is generally recommended. Despite its high prevalence, there is surprisingly limited evidence to inform best clinical practice both at the time of diagnosis and during follow-up. We present 7 vignettes to illustrate common clinical management questions that arise during the course of MGUS. Where evidence is present, we provide a concise summary of the literature and clear recommendations on management. Where evidence is lacking, we describe how we practice and provide a rationale for our approach. We also discuss the potential harms associated with MGUS diagnosis, a topic that is rarely, if ever, broached between patients and providers, or even considered in academic debate.

Free Immunoglobulin Light Chains as Criteria of Extracorporeal Hemocorrection in Patients with Monoclonal Gammopathies

Elimination of free immunoglobulin light chains with the use of EMic2 selective filters was carried out in 12 patients with monoclonal gammopathies and high production of free immunoglobulin light chains. We showed that extracorporeal detoxification for direct removal of excessive free immunoglobulin light chains from the circulation is advisable for these patients, irrespective of the presence and severity of renal insufficiency. Rapid reduction or elimination of free light chains of immunoglobulins in the course of selective extracorporeal elimination helps to prevent the development of irreversible renal failure and to perform adequate antitumor therapy.

Distinct and shared three-dimensional chromosome organization patterns in lymphocytes, monoclonal gammopathy of undetermined significance and multiple myeloma

The consistent appearance of specific chromosomal translocations in multiple myeloma has suggested that the positioning of chromosomes in the interphase nucleus might play a role in the occurrence of particular chromosomal rearrangements associated with malignant transformation. Using fluorescence in situ hybridization, we have determined the positions of selected chromosome pairs (18 and 19, 9 and 22, 4 and 14, 14 and 16, 11 and 14) in interphase nuclei of myeloma cells compared to normal lymphocytes of treatment-naïve patients. All chromosome pairs were arranged in a nonrandom pattern. Chromosomes commonly involved in myeloma-associated translocations (4 and 14, 14 and 16, 11 and 14) were found in close spatial proximity, and this is correlated with the occurrence of overlapping chromosome territories. The spatial distribution of chromosomes may increase the possibility of chromosomal translocations in multiple myeloma.

Nephrotic syndrome secondary to amyloidosis in a patient with monoclonal gammopathy with renal significance (MGRS)

Monoclonal gammopathy with renal significance (MGRS) is a relative new-described entity, diagnosed especially in older patients and deriving from the group with monoclonal gammopathy of undetermined significance (MGUS). Various renal lesions may arise in MGRS, according to the ultrastructural characteristics of the monoclonal immunoglobulin deposition in the kidney, from proliferative glomerulopathies and amyloidosis to light chain proximal tubulopathy and crystal-storing histiocytosis. Although both are considered premalign or non-malignant hematological conditions, kidney involvement in MGRS aggravates the prognosis of the patients and need to be treated aggressively. We discuss the case of a 44-year-old female patient admitted in our Department of Nephrology for clinical picture of impure nephrotic syndrome and decreased renal function associated with Bence-Jones proteinuria. Renal biopsy was performed, and fibrillar amyloid deposits were demonstrated both in glomerular and tubular basement membranes; the immunofluorescence identified the presence of κ chains. Bone marrow aspiration and biopsy showed <10% plasmocytic proliferation confirming the diagnosis of MGRS.

Monoclonal gammopathy-associated pure red cell aplasia

Pure red cell aplasia (PRCA) is a rare disorder characterized by inhibition of erythroid precursors in the bone marrow and normochromic, normocytic anaemia with reticulocytopenia. Among 51 PRCA patients, we identified 12 (24%) patients having monoclonal gammopathy, monoclonal gammopathy of undetermined significance or smouldering multiple myeloma, with presence of monoclonal protein or abnormal serum free light chains and atypical bone marrow features of clonal plasmacytosis, hypercellularity and fibrosis. Thus far, three patients treated with anti-myeloma based therapeutics have responded with reticulocyte recovery and clinical transfusion independence, suggesting plasma cells play a key role in the pathogenesis of this specific monoclonal gammopathy-associated PRCA.

Future Directions in the Evaluation and Treatment of Precursor Plasma Cell Disorders

Multiple myeloma (MM) is an incurable disease that progresses from a premalignant stage termed monoclonal gammopathy of undetermined significance (MGUS) and an intermediate stage of smoldering multiple myeloma (SMM). Recent major advances in therapy with more effective and less toxic treatments have brought reconsideration of early therapeutic intervention in management of SMM, with the goal of reducing progression of the disease before the occurrence of end-organ damage to MM and improving survival. Key to this effort is accurate identification of patients at high risk of progression who would truly benefit from early intervention. In this review, we discuss the current definitions, risk factors, risk stratification, prognosis, and management of MGUS and SMM, as well as new emerging therapeutic options under active investigation.

Five Sequential Evaluations of Renal Histology in a Patient with Light Chain Deposition Disease

A 58-year-old man was referred to our institution for an evaluation of nephrotic range proteinuria. Renal biopsy showed a marked expansion of the mesangial matrix and thickening of glomerular basement membrane (GBM) in periodic acid-silver methenamine (PAM). Immunofluorescence (IF) revealed strong staining for the monoclonal kappa light chain. EM demonstrated massive subendothelial and mesangial dense deposits. As a result, light chain deposition disease (LCDD) was diagnosed. Melphalan and prednisolone (MP) therapy was started, which was continued for 10 years with minimal complications. Serial evaluations of renal histology revealed the resolution of nodular lesions and the glomeruli became nearly normal. MP therapy can therefore be an effective therapeutic option for LCDD if it is continued over the long term.

IgG4-Related Disease: Results From a Multicenter Spanish Registry

IgG4-related disease (IgG4-RD) is a rare entity consisting of inflammation and fibrosis that has been described in multiple organs. Concrete diagnostic criteria have been established recently and there is a lack of large series of patients.To describe the clinical presentation, histopathological characteristics, treatment and evolution of a series of IgG4-RD Spanish patients.A retrospective multicenter study was performed. Twelve hospitals across Spain included patients meeting the current 2012 consensus criteria on IgG4-RD diagnosis.Fifty-five patients were included in the study, 38 of whom (69.1%) were male. Median age at diagnosis was 53 years. Thirty (54.5%) patients were included in the Histologically Highly Suggestive IgG4-RD group and 25 (45.5%) in the probable IgG4-RD group. Twenty-six (47.3%) patients had more than 1 organ affected at presentation. The most frequently affected organs were: retroperitoneum, orbital pseudotumor, pancreas, salivary and lachrymal glands, and maxillary sinuses.Corticosteroids were the mainstay of treatment (46 patients, 83.6%). Eighteen patients (32.7%) required additional immunosuppressive agents. Twenty-four (43.6%) patients achieved a complete response and 26 (43.7%) presented a partial response (<50% of regression) after 22 months of follow-up. No deaths were attributed directly to IgG4-RD and malignancy was infrequent.This is the largest IgG4-RD series reported in Europe. Patients were middle-aged males, with histologically probable IgG4-RD. The systemic form of the disease was frequent, involving mainly sites of the head and abdomen. Corticosteroids were an effective first line treatment, sometimes combined with immunosuppressive agents. Neither fatalities nor malignancies were attributed to IgG4-RD.

Early lesions of the nephron in paraproteinemia

Electron microscopy of renal biopsies in eight patients with paraproteinemia (six multiple myeloma, one Waldenström's disease, one idiopathic paraproteinemia) and without impairment of renal function demonstrates an increase of mesangial matrix and thickening of the lamina rara interna of the basement membrane in the glomerulus by fibrillar material without periodicity. These lesions are thought to exhibit precursors of amyloid deposits. The proximal tubules show signs of increased cellular activity probably because of handling an increased protein load. In the basement membranes there are proteins with a fibrillar structure and definite periodicity. These are suggested to be consistent with large aggregates of immunoglobulin fragments.

Diffuse dermal angiomatosis: a clinical mimicker of vasculitis associated with calciphylaxis and monoclonal gammopathy

Diffuse dermal angiomatosis is a form of cutaneous reactive angiomatosis characterized clinically by painful erythematous or violaceous lesions with ulcers that may mimic cutaneous vasculitis/vasculopathy. Histologically it shows a benign, diffuse proliferation of endothelial cells with tiny blood vessels in the papillary and reticular dermis. Herein, we report four patients with diffuse dermal angiomatosis in the setting of calciphylaxis and monoclonal gammopathy and review the cases previously published in the literature. Comorbidities and management will also be discussed.

Multiple myeloma

This article presents a review of multiple myeloma, precursor states, and related plasma cell disorders. The clinical roles of fluorodeoxyglucose PET/computed tomography (CT) and the potential to improve the management of patients with multiple myeloma are discussed. The clinical and research data supporting the utility of PET/CT use in evaluating myeloma and other plasma cell dyscrasias continues to grow.

A Case of Type I Cryoglobulinemia Associated with a Monoclonal Gammopathy of Undetermined Significance (MGUS)

A 79-year-old Japanese male who had been suffering from renal insufficiency of unknown causes visited us with reddish papules and purpura on both forearms of a month's duration. A skin biopsy was performed from the right forearm, and the histopathology showed an obstruction of superficial blood vessels with eosinophilic amorphous materials suggesting cryoglobulins. Although further investigations revealed the presence of monoclonal immunoglobulin (Ig) G-kappa type I cryoglobulin, a bone marrow biopsy demonstrated that there was 7.6% proliferation of plasmacytoid cells, and the serum level of Ig G was less than 3 g/dl. The diagnosis was type I cryoglobulinemia associated with monoclonal gammopathy of undetermined significance as the possible cause of chronic renal failure. Therefore, purpuric changes on extremities of the elderly, especially those complaining of renal failure should, be taken seriously and not regarded simply as an age-related phenomenon.

IgG4-related kidney disease: MRI findings with emphasis on the usefulness of diffusion-weighted imaging

OBJECTIVES

To investigate the imaging findings of immunoglobulin G4 (IgG4)-related kidney disease (IgG4-KD) on magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) and to evaluate the usefulness of DWI in lesion detection.

METHODS

This retrospective cohort study included 31 patients with IgG4-KD who underwent MRI covering both kidneys. Two radiologists reviewed in consensus the MR images to determine the distribution pattern (location, laterality, and multiplicity) and the visually assessed signal intensity (hypointense, isointense or hyperintense) of the renal lesions compared to the normal renal parenchyma on each sequence. Per-patient sensitivity for detecting IgG4-KD and the number of detectable lesions were compared in T2-weighted images, DWI, and dynamic contrast-enhanced images.

RESULTS

IgG4-KD typically manifested as bilateral (83.9%), multiple (93.5%), and renal parenchymal (87.1%) nodules appearing isointense (93.5%) on T1-weighted images, hypointense (77.4%) on T2-weighted images, hyperintense (100%) on DWI (b=1000), and hypointense (83.3%) in the arterial phase and with a progressive enhancement pattern on dynamic contrast-enhanced images. The sensitivity of DWI for detecting IgG4-KD was significantly higher than that of T2-weighted images (100% vs. 77.4%, P=0.034). The median number of detectable lesions was significantly greater in DWI (n=9) than in T2-weighted images (n=2) and dynamic contrast-enhanced images (n=5) (P≤0.008).

CONCLUSIONS

The characteristic MRI findings of IgG4-KD were bilateral, multiple, renal parenchymal nodules with T2 hypointensity, diffusion restriction, and a progressive enhancement pattern. As DWI was useful in the detection of IgG4-KD, adding DWI to conventional MRI for patients suspected of having IgG4-KD may enhance the diagnosis.

Hepatitis associated with hypereosinophilia suspected to be caused by HES that also presented with the pathological features of IgG4-related disease

A 52-year-old woman presented to our hospital due to elevated liver enzyme levels and hypereosinophilia. Liver biopsy specimens revealed chronic hepatitis with abundant eosinophils and immunoglobulin G4(IgG4)-positive plasma cell infiltration. Systemic lymphadenopathy, including that involving the hepatic hilar lymph nodes, was observed on computed tomography, and the cervical lymph node biopsy specimens exhibited lymphoid follicular hyperplasia and IgG4-positive plasma cell infiltration. It is sometimes difficult to distinguish hypereosinophilic syndrome (HES) from IgG4-related disease, as some of the clinical findings overlap. The numerous areas of eosinophilic infiltration observed in the liver indicated a diagnosis of HES in our case.

Monoclonal gammopathy-associated proliferative glomerulonephritis

Monoclonal gammopathy is characterized by circulating monoclonal immunoglobulin owing to clonal proliferation of immunoglobulin-producing B lymphocytes or plasma cells. Clonal proliferation of B lymphocytes is seen in B-cell lymphoma/leukemia, and clonal plasma cell proliferation is seen in multiple myeloma and monoclonal gammopathy of undetermined significance. The monoclonal immunoglobulin in the setting of a B-cell or plasma cell disorder can cause a proliferative glomerulonephritis via 2 mechanisms: (1) glomerular deposition of the monoclonal immunoglobulin with activation of the classical pathway of complement (direct mechanism), resulting in an immunoglobulin-positive C3-positive glomerulonephritis, and (2) glomerular deposition of complement factors of the alternative and terminal pathway via inhibition of alternative pathway-regulating proteins by the monoclonal immunoglobulin (indirect mechanism), resulting in immunoglobulin-negative C3-positive glomerulonephritis (C3 glomerulopathy). Evaluation should include serum and urine electrophoresis and immunofixation as well as serum-free light-chain assay. If a monoclonal immunoglobulin is detected on these tests, bone marrow biopsy or imaging is needed to exclude more advanced plasma cell dyscrasia. Evaluation of alternative pathway of complement should be done in patients with Ig-negative C3-positive glomerulonephritis. If monoclonal gammopathy is due to an underlying malignant disease such as myeloma, lymphoma, or chronic lymphocytic leukemia, then specific treatment should be aimed at treating the malignant disease, with the goal of eradicating the clonal cells producing the immunoglobulin. In contrast, if monoclonal gammopathy is due to a monoclonal gammopathy of undetermined significance, treatment options include bortezomib, cyclophosphamide, and dexamethasone for a non-IgM monoclonal immunoglobulin and rituximab alone or in combination with cyclophosphamide and dexamethasone for an IgM monoclonal immunoglobulin.

Biclonal light chain gammopathy with aberrant CD33 expression in secondary plasma cell leukemia

Plasma cell leukemia is a rare neoplastic proliferation of circulating plasma cells. Clonal proliferations of plasma cells, such as in plasma cell leukemia or plasma cell myeloma, are typically characterized by production of a monoclonal heavy and/or light chain immunoglobulin. We present a case of a secondary plasma cell leukemia arising from plasma cell myeloma with dual expression of lambda and kappa light chains along with aberrant expression of CD33, CD20, and dim CD56. This case emphasizes the importance of recognizing aberrant immunophenotypes in plasma cell leukemias and represents the first reported case of biclonal light chain expression in a secondary plasma cell leukemia.

B cell lymphoma and myeloma in murine Gaucher's disease

Multiple myeloma and B cell lymphoma are leading causes of death in Gaucher's disease but the nature of the stimulus driving the often noted clonal expansion of immunoglobulin-secreting B cells and cognate lymphoid malignancy is unknown. We investigated the long-term development of B cell malignancies in an authentic model of non-neuronopathic Gaucher's disease in mice: selective deficiency of β-glucocerebrosidase in haematopoietic cells [Gba(tm1Karl/tm1Karl)Tg(Mx1-cre)1Cgn/0, with excision of exons 9-11 of the murine GBA1 gene, is induced by poly[I:C]. Mice with Gaucher's disease showed visceral storage of β-glucosylceramide and greatly elevated plasma β-glucosylsphingosine [median 57.9 (range 19.8-159) nm; n = 39] compared with control mice from the same strain [median 0.56 (range 0.04-1.38) nm; n = 29] (p < 0.0001). Sporadic fatal B cell lymphomas developed in 11 of 21 GD mice (6-24 months) but only two of eight control animals developed tumours by age 24 months. Unexpectedly, most mice with overt lymphoma had absent or few Gaucher cells but local inflammatory macrophages were present. Eleven of 39 of Gaucher mice developed monoclonal gammopathy, but in the control group only one animal of 25 had clonal immunoglobulin abnormalities. Seven of 10 of the B cell lymphomas were found to secrete a monoclonal paraprotein and the lymphomas stained intensely for pan-B cell markers; reactive T lymphocytes were also present in tumour tissue. In the Gaucher mouse strain, it was notable that, as in patients with this disease, CD138(+) plasma cells frequently surrounded splenic macrophages engorged with glycosphingolipid. Our strain of mice, with inducible deficiency of β-glucocerebrosidase in haematopoietic cells and a high frequency of sporadic lethal B cell malignancies, faithfully recapitulates human Gaucher's disease: it serves as a tractable model to investigate the putative role of bioactive sphingolipids in the control of B cell proliferation and the pathogenesis of myelomatosis-the most prevalent human cancer associated with this disorder.

IgG4-related disease and hypertrophic pachymeningitis

Hypertrophic pachymeningitis (HP) is an inflammatory condition in which the dura mater of the cranium or spine becomes thickened, leading to symptoms that result from mass effect, nerve compression, or vascular compromise. The differential diagnosis of HP includes immune-mediated conditions such as rheumatoid arthritis and vasculitis, malignancies, and infections. Many times, no diagnosis is reached; in such cases, the disease has been described as idiopathic HP. IgG4-related disease (IgG4-RD) is a recently described inflammatory condition known to cause tumefactive lesions at myriad anatomical locations. Both IgG4-RD and idiopathic HP share similar demographics, histopathology, and natural history. We hypothesized that IgG4-RD is a common cause of idiopathic HP.To investigate this hypothesis, we identified all pathology specimens diagnosed as noninfectious HP during 25 years at our institution. Fourteen cases had stained slides and paraffin blocks to permit review of the original hematoxylin and eosin stained slides as well as immunostaining of cell blocks. Recently published consensus guidelines describing characteristic histopathology and the necessary quantity of IgG4+ plasma cell infiltrate were used to diagnose IgG4-RD.Four cases (66.6%) that had been regarded previously as representing idiopathic HP were diagnosed as IgG4-RD; of all the reviewed cases, IgG4-RD represented 29% of cases. Of the remaining cases, 3 cases were associated with granulomatosis with polyangiitis (GPA), 2 with lymphoma, and 1 each with rheumatoid arthritis, giant cell arteritis, and sarcoidosis. Two of the cases could not be diagnosed more precisely and were classified as undifferentiated HP. Clinical history, serologic tests, cerebrospinal fluid studies, and radiology alone could not identify the cause of HP. Rather, biopsy with histopathology and immunostaining was necessary to reach an accurate diagnosis. Significant IgG4+ plasma cell infiltrates were observed in rheumatoid arthritis, granulomatosis with polyangiitis, and lymphoma, underscoring the importance of histopathology in making the diagnosis of IgG4-RD.This case series demonstrates that IgG4-RD may be the most common etiology of noninfectious HP and highlights the necessity of biopsy for accurate diagnosis.