Role of the monoclonal kappa chain V domain and reversibility of renal damage in a transgenic model of acquired Fanconi syndrome. (33/119)

Acquired Fanconi syndrome (FS) is a complication of monoclonal gammopathies featuring a generalized dysfunction of the proximal tubule of the kidney, due to the storage within proximal tubular cells of a monoclonal immunoglobulin light chain. We engineered transgenic mice in which the endogenous mouse Jkappa cluster was replaced by a human VkappaJkappa rearranged gene cloned from a patient with smoldering myeloma-associated FS. The V region belonged to the VkappaI subgroup and was related to the O2-O12 germ-line gene, a V segment previously found associated with FS and light-chain crystallization in several patients with myeloma. Association of the human VkappaI domain with a mouse kappa constant domain in transgenic animals yielded a nephrotoxicity pattern similar to that observed in patients, strongly suggesting that the whole pathogenic effect of FS light chains can be ascribed to a peculiar structure of the V domain. Morphologic alterations of the kidney tubular cells, which contained rhomboid-shape crystals, were observed in mice, together with alterations of the proximal tubule reabsorption function. Moreover, the number of renal crystalline inclusions was dramatically reduced after conditional deletion of the human VkappaI transgene, showing that proximal tubular lesions are reversible upon suppression of the nephrotoxic light chain secretion.  (+info)

Hypophosphataemic osteomalacia due to de Toni-Debre-Fanconi syndrome in a 19-year old girl. (34/119)

Osteomalacia associated with adult onset Fanconi syndrome is thought to result from hypophosphataemia due to renal phosphate loss and relative 1,25-dihydroxyvitamin D3 deficiency. In this disorder, the impaired renal phosphate uptake occurs as part of a generalized tubular defect in association with other features such as bicarbonuria, glycosuria and aminoaciduria. Fanconi syndrome is either hereditary--juvenile form--or is associated with various acquired or heritable diseases. In adults, the disease is similar to the juvenile form, but osteomalacia is a prominent feature. We report a sporadic, adult onset, hypophosphataemia in a 19-year old female patient who presented after puberty complaining of bone and joint pain and difficulty in walking following a minor fall. Radiological examination revealed numerous bilateral fractures of the ribs and pelvis while biochemical investigations showed combination of high phosphate clearance, low serum bicarbonate, glycosuria and glycinuria. Known causes of acquired renal tubular dysfunction were ruled out. The patient was diagnosed as having idiopathic Fanconi syndrome and started on vitamin D3 (Alfacalcidol 1 mg/day) and oral phosphorus (Joulie Solution, 1.5 g/day), which led to resolution of symptoms and an increase in serum phosphate (from 0,54 to 0,71 mmol/l) within few months following the initiation of therapy. However, radiological re-examination showed no signs of fracture healing.  (+info)

Dangerous small B-cell clones. (35/119)

The detection of a monoclonal immunoglobulin in serum or urine usually raises concerns about the size of the underlying B-cell-derived clone and possible systemic effects caused by its expansion. However, a small clone can synthesize a very toxic protein, producing devastating systemic damage and protean clinical presentations. The resulting "monoclonal component-related diseases," although difficult to diagnose, may be progressive and even fatal. The monoclonal protein can aggregate and deposit systemically as occurs in light-chain amyloidosis, monoclonal immunoglobulin deposition disease, crystal-storing histiocytosis, and monoclonal cryoglobulinemia. Alternatively, some monoclonal proteins possess antibody activity toward autogenous antigens and cause chronic cold agglutinin disease, mixed cryoglobulinemia, and peripheral neuropathies. Other humoral mediators may contribute to neuropathy in variant disorders such as the POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) syndrome. The clone synthesizing the noxious monoclonal proteins is often small, and sensitive techniques may be required to detect these immunoglobulins. A delay in diagnosis can allow irreversible organ damage and dramatically shorten survival. Prompt recognition of suggestive signs and symptoms should trigger a thorough diagnostic approach to reach the correct diagnosis quickly, because this is the key to effective therapy. Although the treatment of these conditions is not optimal, significant advances have been made, improving the duration and quality of life.  (+info)

Acquired Fanconi's syndrome associated with tenofovir therapy. (36/119)

Tenofovir (Viread) is a nucleotide reverse transcriptase inhibitor introduced into the United States in 2001. It is frequently prescribed not only for its efficacy but also for its decreased side effect profile compared with other nucleoside analogs. It is now increasingly recognized as a cause of acquired Fanconi's syndrome (FS) in human immunodeficient individuals. We describe a case of a patient with AIDS, who, after starting tenofovir therapy, developed myalgias, renal failure, and profound electrolyte abnormalities compatible with the classic features of FS. On discontinuation of tenofovir and replacement of electrolytes, the individual improved clinically with normalization of his renal failure and electrolyte abnormalities. With the success of tenofovir in the anti-HIV drug market, practitioners should remain alert to the possibility of the development of FS. Frequent urine, renal, and electrolyte parameters should be measured at regular intervals following initiation of tenofovir therapy.  (+info)

Excretion of beta 2-glycoprotein I (apolipoprotein H) in renal tubular disease. (37/119)

beta 2-Glycoprotein I (beta 2GI) was identified as a major urinary protein excreted by patients with several renal tubular diseases, including adult Fanconi syndrome, nephrocalcinosis associated with autoimmune diseases, Lowe's syndrome, and Dent's disease (a familial renal tubular disease). Sixteen patients excreted between 2 and 40 mg of beta 2GI per millimole of creatinine. In contrast, 18 healthy controls had undetectable amounts of beta 2GI in urine. Isoelectric focusing followed by immunoblotting demonstrated multiple forms of beta 2GI with pls between 6.4 and 8.2. These pls are higher than for several other "tubular proteins"; beta 2GI may therefore be less retarded than more-anionic proteins by the glomerular charge-barrier. This could explain why large quantities of beta 2GI are excreted despite its relatively high molecular mass (50 kDa). Excretion of beta 2GI was easily demonstrated by routine electrophoresis of urine proteins. beta 2GI migrates in the beta-gamma region and may be confused with Bence Jones protein. beta 2GI is stable for at least two years in urine frozen at -25 degrees C.  (+info)

Association between ABCC2 gene haplotypes and tenofovir-induced proximal tubulopathy. (38/119)

BACKGROUND: Tenofovir disoproxil fumarate (TDF) may induce renal proximal tubulopathy (rPT). There are no data on pharmacogenomic predictors of rPT in the genes encoding the multidrug-resistance protein (MRP) 2 and MRP4 transporters. METHODS: Mutational screening of the genes for MRP2 (ABCC2) and MRP4 (ABCC4) was performed using genomic DNA from 13 human immunodeficiency virus type 1 (HIV-1)-infected patients (group 1) presenting with TDF-induced rPT. Concomitantly, 17 unrelated HIV-1-infected patients who had received TDF therapy and who did not have rPT (group 2) were included in a case-control analysis, to assess the influence of single-nucleotide polymorphisms (SNPs) identified in ABCC2 and ABCC4. RESULTS: Six SNPs were identified in ABCC2. A significant allelic association between the 1249 G-->A SNP and TDF-induced rPT was observed (odds ratio, 6.11 [95% confidence interval, 1.19-31.15]; P<.02). ABCC2 haplotypes were significantly associated with the onset of TDF-induced rPT--CATC appeared to be a predisposing haplotype, as it was found in 40.9% of the group 1 case patients and in 13.7% of the group 2 control subjects (P<.01), whereas CGAC appeared to be a protective haplotype, as it was not observed in the group 1 case patients but was present in 20.2% of the group 2 control subjects (P<.01). No association was observed between ABCC4 polymorphism and TDF-induced rPT in the present study. CONCLUSION: ABCC2 haplotypes are associated with rPT induced by TDF in HIV-1-infected patients.  (+info)

Abacavir-induced reversible Fanconi syndrome with nephrogenic diabetes insipidus in a patient with acquired immunodeficiency syndrome. (39/119)

There are several reports of Fanconi syndrome (FS) with or without nephrogenic diabetes insipidus (NDI) in patients with human immunodeficiency virus (HIV) infection, treated with various antiretroviral medications like cidofovir, adefovir, didenosine and tenofovir. But neither FS nor NDI has been documented with abacavir therapy. We are reporting the first case of abacavir-induced reversible FS with NDI in a patient with acquired immunodeficiency syndrome, who recovered completely with supportive treatment and discontinuation of abacavir.  (+info)

A patient with cystinosis presenting transient features of Bartter syndrome. (40/119)

A 16-month-old boy was admitted to the clinic because of vomiting and growth failure. His weight and height measurements were under the fifth percentile. He had fair hair and skin, enlarged wrists and rachitic rosaries. The presence of metabolic alkalosis, hypokalemia, hypochloremia, and high renin and aldosterone levels were suggestive of Bartter syndrome. However, in view of the growth failure, fair hair and skin, proteinuria, polyuria and active rickets, cystinosis was considered. Bone marrow smear examination was normal, despite the existence of suspicious crystals in the cornea. Cystine crystals were seen in the conjunctiva biopsy and increased leukocyte cystine level was measured; therefore, definitive cystinosis diagnosis was made. Renal Fanconi syndrome with metabolic acidosis is prominent in cystinosis; however, in rare instances, if sodium-dependent trans-tubular transport defect is present, patients could have Bartter syndrome findings such as hypochloremic metabolic alkalosis. Our case is a good example demonstrating that metabolic alkalosis should not exclude cystinosis and the other signs and symptoms of the patient should be thoroughly evaluated.  (+info)