Acquired fanconi syndrome with osteomalacia secondary to monoclonal gammopathy of undetermined significance

Band-shaped keratopathy in HNF4A-related Fanconi syndrome: a case report and review of the literature

BACKGROUND

Fanconi's syndrome (FS) is characterized by type-2 renal tubular acidosis, short stature, and renal rickets, along with glycosuria, aminoaciduria, hypophosphaturia, and urinary bicarbonate wasting. The genetic form of FS has been linked to HNF4A variants. Although additional clinical features such as hearing impairment have recently been associated with HNF4A-linked FS, its ocular manifestation has not been described.

MATERIAL AND METHODS

Presenting a case of a 5-year-old male child with bilateral progressive corneal opacification and the presence of bilateral greyish-white deposits in the interpalpebral region since infancy. A next-generation sequencing (NGS)-based genetic testing was performed for the child followed by parental genetic testing for the identified variant. Furthermore, relevant works of literature were reviewed related to this condition.

RESULTS

Detailed corneal findings showed a bilateral band-shaped keratopathy (BSK) in the patient. Physical and systemic findings showed signs consistent with FS. Sequencing analysis revealed a novel heterozygous c.635C>T, (p.Pro212Leu) variant in the HNF4A gene in the proband and mother, while the father had a normal genotype.

CONCLUSIONS

Our case highlights the occurrence of BSK in an exceptionally rare manifestation of hereditary FS linked to HNF4A gene variant. The variant exists both in proband and asymptomatic mother. Therefore, the variable penetrance which is known to exist in HNF4A is acknowledged in this context. This report suggests the first documented instance establishing a plausible connection between BSK and HNF4A-associated FS, characterized by the variable penetrance attributed to the HNF4A gene.

A Rare Case of Acquired Fanconi's Syndrome With Monoclonal Gammopathy in an Infant

BACKGROUND

Monoclonal gammopathies associated with acquired Fanconi's syndrome (AFS) have been reported in the adult population. AFS is characterized by renal dysfunction resulting in proteinuria, aminoaciduria, hypophosphatemia, glucosuria, and hyperchloremic metabolic acidosis. In this case report, we document the clinical and laboratory findings of a preterm infant with features of both AFS and monoclonal gammopathy in the urine.

METHODS

Clinical suspicion of AFS prompted the following laboratory studies to be performed: urine protein electrophoresis (UPEP), urine immunofixation, and urine amino acid analysis with high performance liquid chromatography (HPLC).

RESULTS

Urine amino acid analysis revealed aminoaciduria. On UPEP, nonselective glomerular proteinuria was seen with a faint band in the gamma region. Urine immunofixation confirmed the presence of a monoclonal IgG lambda component with free monoclonal lambda light chains.

CONCLUSION

To the best of our knowledge, this is the first case of pediatric AFS reported with a monoclonal gammopathy and monoclonal free light chains.

The reduced expression of proximal tubular transporters in acquired Fanconi syndrome with κ light chain deposition

In a case of acquired Fanconi syndrome associated with smoldering myeloma, we confirmed the deposition of protease-resistant κ light chain proteins in a proximal tubular injury and found the decreased expression of apical tubular transporters including sodium glucose co-transporter, sodium phosphate co-transporter, uric acid transporter 1, and a decrease of Na(+)/K(+)-ATPase in the basolateral membrane. The protease-resistant kappa light chain has a pathological role in the expression of tubular transporters in the proximal tubule and causes Fanconi syndrome associated with smoldering myeloma.

Acquired Fanconi syndrome due to long-term adefovir administration in a patient with IgG-kappa monoclonal gammopathy and kappa Bence-Jones protein

A 77-year-old man was admitted to our hospital for a right femoral neck fracture. He had been prescribed lamivudine for chronic hepatitis B infection for 11 years, and adefovir was added 5 years ago. After hospitalization, a right femoral head prosthesis was performed successfully, but an unknown hypokalemia was revealed. Hypophosphatemia, hypouricemia, glucosuria, and panaminoaciduria were also revealed, and multiple microfractures were detected by bone scintigraphy. We diagnosed him as 'osteomalacia associated with Fanconi syndrome,' which was likely due to the adefovir. Moreover, a monoclonal IgG-kappa and a kappa Bence-Jones protein were detected in his serum and urine, respectively. We switched from adefovir plus lamivudine to entecavir and started calcitriol. His excessive urinary β2-microglobulin excretion and glucosuria had decreased dramatically at 10 weeks after the modification of drugs; those of the phosphate, uric acid and total protein, however, continued. Renal biopsy specimens obtained at 10 weeks after discontinuation of adefovir revealed focal tubular atrophic changes with/without inflammatory cells, which were predominantly observed next to glomeruli. Kappa-dominant staining was not observed in either glomeruli or tubules with immunostaining by the enzyme-labeled antibody method. Electron microscopy revealed neither crystalline structures in the cytoplasm of proximal tubules nor electron-dense deposits. Because of the remarkable proportional reduction of other urinary protein fractions, urinary M-peak appeared 26 weeks after discontinuation of adefovir, but the net amounts of the fraction decreased gradually.

Acute kidney injury in a patient with polyarteritis nodosa and multiple myeloma

We herein report the case of a Japanese man with polyarteritis nodosa (PAN) accompanied by multiple myeloma (MM). The patient was diagnosed with PAN. Concurrently, IgG kappa paraprotein was detected, and bone marrow changes indicative of MM were observed. Prednisolone (PSL) administered at a dose of 30 mg/day was initiated; however, the serum creatinine level increased. In spite of increasing the dose of PSL to 45 mg/day and initiating treatment with double filtration plasmapheresis, the patient's renal dysfunction continued to progress and haemodialysis was introduced. He died from pneumonia 12 months after admission. We conclude that renal failure is an important risk factor in the prognosis of PAN accompanied by MM.

Ailing bones and failing kidneys: a case of chronic cadmium toxicity

Heavy metal toxicity is often caused by occupational exposure. Chronic cadmium toxicity is a significant health concern among workers engaged in zinc smelting, battery production and silver jewellery industries, particularly in developing countries. We report the case of a 48-year-old man who presented with severe osteoporosis, impaired renal function and acquired Fanconi syndrome. He was finally diagnosed with chronic cadmium toxicity resulting from long-term occupational exposure. Cadmium has a long biological half-life and there is no effective treatment for people who are exposed to it. Therefore, an early diagnosis and prevention of further exposure are important.

Development of Renal Failure without Proteinuria in a Patient with Monoclonal Gammopathy of Undetermined Significance: An Unusual Presentation of AL Kappa Amyloidosis

AL amyloidosis complicating monoclonal gammopathy of undetermined significance (MGUS) has usually a predominant glomerular deposition of lambda light chain. Heavy proteinuria is one of its cardinal manifestations. A 78-year-old man with a 9-year history of IgG kappa light-chain-MGUS and normal urine protein excretion developed severe renal failure. Serum levels of kappa light chain and serum IgG had been stable while proteinuria was absent throughout the nine-year period. For the first eight years, he had stable stage III chronic kidney disease attributed to bladder outlet obstruction secondary to prostatic malignancy. In the last year, he developed progressive serum creatinine elevation, without any increase in the serum or urine levels of paraproteins or any sign of malignancy. Renal ultrasound and furosemide renogram showed no evidence of urinary obstruction. Renal biopsy revealed AL amyloidosis, with reactivity exclusive for kappa light chains, affecting predominantly the vessels and the interstitium. Glomerular involvement was minimal. Melphalan and prednisone were initiated. However, renal function continues deteriorating. Deposition of AL kappa amyloidosis developing during the course of MGUS predominantly in the wall of the renal vessels and the renal interstitium, while the involvement of the glomeruli is minimal, leads to progressive renal failure and absence of proteinuria. Renal biopsy is required to detect both the presence and the sites of deposition of renal AL kappa light chain amyloidosis.