Heavy Chain Deposition Disease: Clinicopathologic Characteristics of a Chinese Case Series.

RATIONALE & OBJECTIVE: Heavy chain deposition disease (HCDD) is a rare consequence of monoclonal immunoglobulin deposition disease that has not been well characterized in non-white populations. To explore the clinicopathologic characteristics and outcomes of HCDD in Chinese individuals, we report on a case series assembled in a single center in China. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: 25 patients with biopsy-proven HCDD were studied retrospectively. RESULTS: 14 men and 11 women with an average age of 50.3 years were studied. The patients presented with hypertension (76%), edema (96%), anemia (84%), serum creatinine level > 1.2mg/dL (68%), nephrotic-range proteinuria (56%), and microscopic hematuria (80%). One (4%) patient had multiple myeloma diagnosed. Serum immunofixation electrophoresis showed that 10 of 21 (48%) patients were positive for monoclonal immunoglobulin. Hypocomplementemia of C3 was found in 68% of patients. Nodular mesangial sclerosis was identified in all patients by using light microscopy. Using immunofluorescence, all 25 patients had deposition of heavy chains of immunoglobulin G class (γ1, 13; γ2, 2; γ3, 6; γ4, 2; γ1 and γ4, 1; and γ2 and γ4, 1). During an average of 40.1 months of follow-up of 20 patients, 65% had improved kidney function, 10% had worsening kidney function, and 25% progressed to kidney failure. Mean values for kidney and patient survival were 37.8 and 40.1 months, respectively. Kidney survival was higher among patients who received chemotherapy. LIMITATIONS: Retrospective study, single-center experience. CONCLUSIONS: In this case series of HCDD in a single center in China, the heavy chain deposits seen in the kidney biopies of all individuals were of immunoglobulin G class. Chemotherapy improved kidney function, especially among individuals in an early stage of the disease.

The clinicopathologic characteristics of kidney diseases related to monotypic IgA deposits.

Monoclonal gammopathy of renal significance (MGRS) regroups renal disorders caused by a monoclonal immunoglobulin without overt hematological malignancy. MGRS includes tubular disorders, glomerular disorders with organized deposits, and glomerular disorders with non-organized deposits, such as proliferative glomerulonephritis with monoclonal IgG deposits. Since glomerular involvement related to monotypic IgA deposits is poorly described we performed retrospective analysis and defined clinico-biological characteristics, renal pathology, and outcome in 19 referred patients. This analysis allowed distinction between 2 types of glomerulopathies, α-heavy chain deposition disease (5 patients) and glomerulonephritis with monotypic IgA deposits (14 patients) suggestive of IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits in 12 cases. Clinicopathologic characteristics of α-heavy chain deposition disease resemble those of the γ-heavy chain disease, except for a higher frequency of extra-capillary proliferation and extra-renal involvement. IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits should be differentiated from diseases with polytypic IgA deposits, given distinct clinical, histological, and pathophysiological features. Similarly to IgG-proliferative glomerulonephritis with monoclonal immunoglobulin deposits, overt hematological malignancy was infrequent, but sensitive serum and bone marrow studies revealed a subtle plasma cell proliferation in most patients with IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Anti-myeloma agents appeared to favorably influence renal prognosis. Thus, potential progression towards symptomatic IgA multiple myeloma suggests that careful hematological follow-up is mandatory. This series expands the spectrum of renal disease in MGRS.

Unravelling the immunopathological mechanisms of heavy chain deposition disease with implications for clinical management.

Randall-type heavy chain deposition disease (HCDD) is a rare disorder characterized by tissue deposition of a truncated monoclonal immunoglobulin heavy chain lacking the first constant domain. Pathophysiological mechanisms are unclear and management remains to be defined. Here we retrospectively studied 15 patients with biopsy-proven HCDD of whom 14 presented with stage 3 or higher chronic kidney disease, with nephrotic syndrome in 9. Renal lesions were characterized by nodular glomerulosclerosis, with linear peritubular and glomerular deposits of γ-heavy chain in 12 patients or α-heavy chain in 3 patients, without concurrent light chain staining. Only 2 patients had symptomatic myeloma. By serum protein electrophoresis/immunofixation, 13 patients had detectable monoclonal gammopathy. However, none of these techniques allowed detection of the nephrotoxic truncated heavy chain, which was achieved by immunoblot and/or bone marrow heavy chain sequencing in 14 of 15 patients. Serum-free kappa to lambda light chain ratio was abnormal in 11 of 11 patients so examined. Immunofluorescence studies of bone marrow plasma cells showed coexpression of the pathogenic heavy chain with light chain matching the abnormal serum-free light chain in all 3 tested patients. Heavy chain sequencing showed first constant domain deletion in 11 of 11 patients, with high isoelectric point values of the variable domain in 10 of 11 patients. All patients received chemotherapy, including bortezomib in 10 cases. Renal parameters improved in 11 patients who achieved a hematological response, as assessed by normalization of the free light chain ratio in 8 cases. Tissue deposition in HCDD relates to physicochemical peculiarities of both variable and constant heavy chain domains. Early diagnosis and treatment with bortezomib-based combinations appear important to preserve renal prognosis. Thus, monitoring of serum-free light chain is an indirect but useful method to evaluate the hematological response.

Gamma Heavy Chain Disease with T-cell Large Granular Lymphocytic Leukemia: A Case Report and Review of the Literature.

Gamma heavy chain disease (gHCD) is a rare lymphoproliferative disorder characterized by the production of a truncated immunoglobulin heavy chain. Although some cases of gHCD are concurrent with other lymphoid neoplasms, few have been reported. We herein present the case of a 73-year-old woman with gHCD and T-cell large granular lymphocytic leukemia. A multiparameter flow cytometry analysis revealed neoplastic cells that were positive for CD28, a marker of T-cell activation, the anti-apoptotic antigen of neoplastic plasma cells, CD38 and CD45. The results of this multiparameter flow cytometry analysis may contribute to furthering the understanding of the clinicopathological features of gHCD.

A mouse model recapitulating human monoclonal heavy chain deposition disease evidences the relevance of proteasome inhibitor therapy.

Randall-type heavy chain deposition disease (HCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a truncated monoclonal immunoglobulin heavy chain (HC) bearing a deletion of the first constant domain (CH1). We created a transgenic mouse model of HCDD using targeted insertion in the immunoglobulin κ locus of a human HC extracted from a HCDD patient. Our strategy allows the efficient expression of the human HC in mouse B and plasma cells, and conditional deletion of the CH1 domain reproduces the major event underlying HCDD. We show that the deletion of the CH1 domain dramatically reduced serum HC levels. Strikingly, even with very low serum level of truncated monoclonal HC, histologic studies revealed typical Randall-type renal lesions that were absent in mice expressing the complete human HC. Bortezomib-based treatment resulted in a strong decrease of renal deposits. We further demonstrated that this efficient response to proteasome inhibitors mostly relies on the presence of the isolated truncated HC that sensitizes plasma cells to bortezomib through an elevated unfolded protein response (UPR). This new transgenic model of HCDD efficiently recapitulates the pathophysiologic features of the disease and demonstrates that the renal damage in HCDD relies on the production of an isolated truncated HC, which, in the absence of a LC partner, displays a high propensity to aggregate even at very low concentration. It also brings new insights into the efficacy of proteasome inhibitor-based therapy in this pathology.

A unique description of stage IV extranodal marginal zone lymphoma (EMZL) in an adolescent associated with gamma heavy chain disease.

Extranodal Marginal zone lymphoma (EMZL) is a rare, usually localized disease in children. Advanced stage EMZL in adults is considered incurable, with prolonged remissions after chemotherapy. Gamma heavy chain disease (γHCD) is a rare disease of adults associated with lympho-proliferative processes with no comparable reports in children. A case of stage-IV EMZL with γHCD in an adolescent is discussed including treatment with Bendamustine plus Rituximab. The patient remains disease free 18 months from diagnosis. This case highlights necessity for careful diagnostic work-up to identify indolent lymphomas in children which may respond to less toxic chemotherapy than used for common pediatric lymphomas.

A unique case of γ-heavy chain deposition disease characterized by concomitant deposition of γ2 and γ4 subclasses.

Heavy chain deposition disease (HCDD) is a rare entity. γ-HCDD is the predominant subtype and is characterized by glomerular and tubular deposition of a single γ-heavy chain subclass. To our knowledge, γ-HCDD with simultaneous deposition of two subclasses has not yet been described. A 39-year-old woman presented with hypertension, nephrotic syndrome, anemia, microscopic hematuria and progressive renal dysfunction. A light microscopic examination of renal biopsy specimens showed nodular glomerulosclerosis. Electron microscopy revealed electron-dense deposits along the glomerular and tubular basement membranes. Immunofluorescence microscopy showed positive glomerular and tubular staining for immunoglobulin G (IgG) and negative staining for κ and λ light chains. An analysis of the IgG subclass showed positive staining for both IgG2 and IgG4. We herein describe a unique case of γ-HCDD with concurrent deposition of two subclasses, presenting a new subtype to the disease spectrum.

Acquired cutis laxa associated with heavy chain deposition disease involving dermal elastic fibers.

IMPORTANCE: Acquired cutis laxa is a rare cutaneous manifestation of hematologic malignancy. We report a case of γ heavy chain deposition disease (HCDD) associated with acquired cutis laxa, renal involvement, and hypocomplementemia and propose a mechanism of elastic fiber degradation in the skin of this patient with HCDD. OBSERVATIONS: To determine the localization of immunoglobulin heavy chains and complement activation in the skin of a patient with HCDD, we examined her skin biopsy specimens under light and electron microscopy. Analysis demonstrated the deposition of γ heavy chain and complement components C1q and C3 on the surfaces of dermal elastic fibers, indicating complement fixation by the deposited heavy chains. Electron microscopy revealed finely granular electron-dense deposits coating the surfaces of frayed dermal elastic fibers. CONCLUSIONS AND RELEVANCE: The pathogenesis of cutis laxa in this condition is poorly understood. We hypothesize a mechanism of elastic tissue destruction by complement fixation with resultant activation of the complement cascade ultimately causing elastolysis. Based on our findings and those of other reports, we propose that skin heavy chain deposition can serve as a marker of plasma cell secretory activity in HCDD, although further studies are needed.

The heavy chain diseases: clinical and pathologic features.

Heavy chain diseases are a family of rare, systemic syndromes typically associated with or representing a variant of a B-cell neoplasm. Their characteristic feature is production of a mutated immunoglobulin heavy chain incapable of either partnering with light chains in the formation of a full immunoglobulin molecule or of being degraded by the proteasome. The abnormal heavy chain is detected in urine and/or serum without an associated light chain, a pathognomonic finding. Depending on the subtype of the altered heavy chain, these conditions can be subclassified as alpha, gamma, or mu heavy chain disease. We discuss the clinical presentation; epidemiology; laboratory, radiologic, and pathologic features; and treatment options for each of the heavy chain diseases, emphasising the importance of an accurate pathologic diagnosis and correct interpretation of immunologic studies in their identification.

A case of renal γ2 heavy-chain deposition disease accompanied by rapid progressive renal failure.

BACKGROUND: The recently described heavy-chain deposition disease (HCDD) is a comparatively rare monoclonal immunoglobulin disorder characterized histopathologically by glomerular and tubular basement membrane deposition of nonamyloidotic monoclonal heavy chains without associated light chains. METHOD: We have described a case of γ2-HCDD presenting with proteinuria, microhematuria, severe hypertension, and rapidly progressive renal failure, which serum creatinine level was only 1.52 mg/dL in early stage HCDD, and the clinicopathologic features of this case have been compared with other reported cases of γ2-HCDD. RESULTS: Renal biopsy disclosed nodular sclerosing glomerulopathy. Immunofluorescence analysis revealed IgG2 (2+) heavy chain and C3 (+) in the mesangium and along the capillary walls and tubular basement membranes without IgA, IgM, κ and λ light chains. Electron microscopy revealed electron-dense deposits along the glomerular and tubular basement membranes as well as in the mesangium. Moreover, regardless of therapy, the condition of the patient progressively deteriorated, with less than 3 months of renal survival. CONCLUSION: Rapid progressive renal failure was a common feature in both cases of γ2-HCDD. We propose that a possible link exists between prognosis of renal HCDD and the subclass of heavy chain deposited in the kidney.

Analysis of patients with γ-heavy chain disease by the heavy/light chain and free light chain assays.

BACKGROUND: The objective of this study was to evaluate the performance of the heavy/light chain and free light chain immunoassays in patients with heavy chain disease, and to assess the ability of the heavy/light chain assay to measure and confirm the abnormal, truncated heavy chain. METHODS: Frozen serum samples from 15 γ-heavy chain disease patients were tested for IgGκ, IgGλ, total IgG, free light chains, and M-spike concentrations. RESULTS: The (Gκ+Gλ)/IgGtotal ratio for these 15 patients ranged from 0.02 to 0.80. The 10 patients with IgG concentrations above 1 g/dL all had ratios below 0.3 indicating that a substantial portion of IgG was not quantitated by the Gκ and Gλ reagents. The average M-spike was 1.61 g/dL and the average calculated abnormal γ-chain concentration was 2.94 g/dL. Additionally, free light chain analysis revealed the presence of monoclonal free κ light chain in three of the 15 patients. CONCLUSIONS: This study demonstrates utility of a nephelometric assay to identify truncated immunoglobulin heavy chains in γ-HCD and that 20% of these patients also have monoclonal free light chain.