[Hyperphosphatemic pseudotumoral calcinosis due to FGF23 mutation with secondary amyloidosis]

A 44 years old man was admitted for nephrotic syndrome and rapidly progressive renal failure. Two firm, tumour-like masses were localized around the left shoulder and the right hip joint. Since the age of 8 years old, the patient had a history of metastatic calcification of the soft tissues suggesting hyperphosphatemic pseudotumoral calcinosis. Despite treatment for a long time with phosphate binders the metastatic calcinosis had to be removed with several surgeries. The patient had also a history of recurrent fever associated with pain localized toward the two masses and underwent multiple antibiotic courses. Laboratory findings at admission confirmed nephrotic syndrome. S-creatinine was 2.8 mg/dl. Calcium was 8.4 mg/dl, Phosphorus 8.2 mg/dl, PTH 80 pg/ml, 25 (OH)VitD 8 ng/ml. Serum amyloid A was slightly increased. We performed renal biopsy and we found AA amyloid deposits involving the mesangium and the tubules. The bone marrow biopsy revealed the presence of AA amyloid in the vascular walls. During the next two months renal failure rapidly progressed and the patient started hemodialysis treatment. We performed genetic analysis that confirmed homozygous mutation of the FGF23 gene. After 14 months on hemodialysis, the patient's lesions are remarkably and significantly reduced in dimension. The current phosphate binder therapy is based on sevelamer and lanthanum carbonate. Serum amyloid A is persistently slightly increased as well as C reactive protein. Proteinuria is in the nephrotic range without nephrotic syndrome.

The risks associated with percutaneous native kidney biopsies: a prospective study

BACKGROUND

The known risks and benefits of native kidney biopsies are mainly based on the findings of retrospective studies. The aim of this multicentre prospective study was to evaluate the safety of percutaneous renal biopsies and quantify biopsy-related complication rates in Italy.

METHODS

The study examined the results of native kidney biopsies performed in 54 Italian nephrology centres between 2012 and 2020. The primary outcome was the rate of major complications 1 day after the procedure, or for longer if it was necessary to evaluate the evolution of a complication. Centre and patient risk predictors were analysed using multivariate logistic regression.

RESULTS

Analysis of 5304 biopsies of patients with a median age of 53.2 years revealed 400 major complication events in 273 patients (5.1%): the most frequent was a ≥2 g/dL decrease in haemoglobin levels (2.2%), followed by macrohaematuria (1.2%), blood transfusion (1.1%), gross haematoma (0.9%), artero-venous fistula (0.7%), invasive intervention (0.5%), pain (0.5%), symptomatic hypotension (0.3%), a rapid increase in serum creatinine levels (0.1%) and death (0.02%). The risk factors for major complications were higher plasma creatinine levels [odds ratio (OR) 1.12 for each mg/dL increase, 95% confidence interval (95% CI) 1.08-1.17], liver disease (OR 2.27, 95% CI 1.21-4.25) and a higher number of needle passes (OR for each pass 1.22, 95% CI 1.07-1.39), whereas higher proteinuria levels (OR for each g/day increase 0.95, 95% CI 0.92-0.99) were protective.

CONCLUSIONS

This is the first multicentre prospective study showing that percutaneous native kidney biopsies are associated with a 5% risk of a major post-biopsy complication. Predictors of increased risk include higher plasma creatinine levels, liver disease and a higher number of needle passes.

[Genetics and nosological classification of renal cystic diseases]

Renal cystic diseases are the major group of inherited renal disorders in humans and a leading cause of end-stage renal disease. Dominant and recessive polycystic kidney disease (ADPKD and ARPKD, respectively) account for most of the clinical conditions. However, nephronophthisis (NPHP), medullary cystic kidney disease (MCKD), and dominant glomerulocystic kidney disease (GCKD) still have a relevant clinical impact, particularly in children. The discovery that the proteins that are defective in ADPKD and ARPKD localize to the primary cilium and the recognition of the role of this organelle in cystogenesis have led to the term ''ciliopathies''. In the last decade, the list of ciliopathies has continued to grow. Analysis of the protein products of the nine NPHP genes (NPHP 1-9) evinced a strong relation between ciliary function and pathogenesis of NPHP. The oral-facial-digital syndrome (OFD) type I, characterized by congenital malformations and cystic kidney disease, was found to result from mutations in the OFD1 gene, which encodes a protein located to the primary cilium. Parallel to these advances, mutations in UMOD, the gene encoding uromodulin, were identified in pedigrees with MCKD2, familial juvenile hyperuricemic nephropathy, and autosomal dominant GCKD. In all these disorders, uromodulin was found to be accumulating in intracellular aggregates, suggesting a common pathogenesis. Taken together, these findings suggest the need for the separation of renal cystic diseases due to UMOD mutations (uromodulin-associated diseases) from renal cystic diseases related to mutation of genes encoding for proteins expressed in the primary cilium (ciliopathies).

[Atheroembolic renal disease]

Atheroembolic renal disease can be defined as renal failure due to occlusion of the renal arterioles by cholesterol crystal emboli usually dislodged from ulcerated atherosclerotic plaques of the aorta. Atheroembolic renal disease is part of multisystem disease, since the embolization usually involves other organ systems such as the gastrointestinal system, central nervous system, and lower extremities. The kidney is frequently involved because of the proximity of the renal arteries to the abdominal aorta, where erosion of atheromatous plaques is most likely to occur. Embolization may occur spontaneously or after angiographic procedures, vascular surgery, and anticoagulation. In the last decade, atheroembolic renal disease has become a recognizable cause of renal disease. An ante-mortem diagnosis of the disease is possible in a significant proportion of cases as long as the level of diagnostic suspicion is high. The disease can severely affect kidney and patient survival. Although no specific treatment has been proven efficacious, use of statins may be justifiable and such therapy would be a reasonable choice for future treatment trials.

[Choosing the right treatment approach in focal and segmental glomerular sclerosis with chronic renal failure]

Focal and segmental glomerular sclerosis (FSGS) is a heterogeneous disease from a clinical, etiological and clinical point of view. FSGS may be idiopathic, usually associated with nephrotic syndrome, which requires an ''etiological'' treatment approach. In addition, hereditary and secondary forms of FSGS have been described. The response to therapy, including steroids, cytotoxic drugs and calcineurin inhibitors, is considered the best clinical indicator of outcome. Many uncertainties exist regarding the best therapeutic approach to FSGS in patients presenting with chronic renal failure. In this setting, before planning any treatment, the physician should always assess the presence of superimposed functional renal insufficiency and evaluate the severity of the renal impairment, the histological picture, previous immunosuppressive treatments, and the individual patient's risk for side effects. Keeping in mind these considerations and in the absence of appropriate studies, we can formulate the following suggestions: 1. there is no absolute contraindication to the use of full-dose prednisone as initial therapy, although the likelihood of a good response is low; 2. the use of cytotoxic drugs is not recommended unless the patient presents with a steroid-responsive form of the disease; 3. in patients with a glomerular filtration rate of less than 40 mL/min, the use of calcineurin inhibitors should be avoided.

[Atheroembolic renal disease: a diagnostic challenge]

Atheroembolic renal disease is a part of a multisystem disease and can be defined as renal failure secondary to the occlusion of renal arterioles and glomerular capillaries with cholesterol crystal emboli deriving from the aorta and other major arteries. The kidney is usually involved because of the proximity of the renal arteries to abdominal aorta (where the erosion of atheromatous plaque is most likely to occur), and the high renal blood flow. Cholesterol crystal embolism can also occur in other visceral organs, as well as in the upper and lower extremities. Embolization may occur spontaneously or after angiographic and surgical procedures, and anticoagulation. Atheroembolic renal disease is an important yet underdiagnosed component of the spectrum of kidney diseases associated with atherosclerosis and remains an unexplored field of nephrology research.

[Renal involvement in systemic sclerosis]

Systemic sclerosis is an autoimmune disease characterized by fibrosis of the skin and internal organs. Raynaud's phenomenon generally precedes other disease manifestations. The distribution of skin lesions and the internal organ involvement are the basis for the classification into limited and diffuse forms of the disease. Clinically evident renal disease is observed in 10-40% of patients. The most common renal presentation is renal crisis, characterized by acute onset of renal failure and severe hypertension; some patients remain normotensive, showing microangiopathic hemolytic anemia. Renal complications due to penicillamine may occur in some patients. Finally, ANCA-associated glomerulonephritis is a rare complication of the disorder. In spite of treatment with ACE inhibitors, 20-50% of patients with renal crisis progress to end-stage renal disease. In the absence of a specific therapy, there is accumulating evidence supporting the effectiveness of prostacyclin derivatives, antifibrotic and immunosuppressive drugs. The evidence is strong that the ACE inhibitors that are used in renal crisis are disease modifying. In our series including 193 patients with systemic sclerosis, renal involvement was observed in 19 patients; 11 presented renal crisis (hypertensive in 8; normotensive in 3); 5 had chronic nephropathy; 2 developed penicillamine-induced nephrotic syndrome, and 1 ANCA-associated glomerulonephritis. Renal disease occurs in a minority of patients with systemic sclerosis, and may have a variable clinicopathological picture. As renal involvement is associated with a worse prognosis, careful monitoring of blood pressure, urine chemistry and renal function is required, particularly in patients with diffuse skin disease.

Cholesterol crystal embolism (atheroembolism)

Cholesterol crystal embolism, known as atheroembolic disease, is caused by showers of cholesterol crystals from an atherosclerotic plaque that occludes small arteries. Embolization can occur spontaneously or as an iatrogenic complication from an invasive vascular procedure (angiography or vascular surgery) and after anticoagulant therapy. The atheroembolism can give rise to different degrees of renal impairment. Some patients show a moderate loss of renal function, others severe renal failure requiring dialysis. Renal outcome can be variable: some patients deteriorate or remain on dialysis, some improve and some remain with chronic renal impairment. Clinically, three types of atheroembolic renal disease have been described: acute, subacute or chronic. More frequently a progressive loss of renal function occurs over weeks. Atheroembolization can involve the skin, gastrointestinal system and central nervous system. The diagnosis is difficult and controversial for the protean extrarenal manifestations. In the past, the diagnosis was often made post-mortem. In the last 10 yrs, awareness of atheroembolic renal disease has improved. The correct diagnosis requires the clinician to be alert. The typical patient is a white male aged >60 yrs with a history of hypertension, smoking and arterial disease. The presence of a classic triad (precipitating event, renal failure and peripheral cholesterol crystal embolization) suggests the diagnosis. This can be confirmed by a biopsy of the target organs. A specific treatment is lacking; however, it is an important diagnosis to make because an aggressive therapeutic approach can be associated with a more favorable clinical outcome.

Access site-related infection in dialysis: the AStRID project: a multicenter prospective Italian study

A multicenter prospective study has been planned, in a large sample of Italian end-stage renal disease (ESRD) patients, aiming to assess the vascular access (VA) site-related infection rates and to identify variables associated with them. All ESRD patients undergoing chronic hemodialysis (HD) in the participating centers will be enrolled in the study. Participating centers were selected on a voluntary basis. Patients will be enrolled within an 18-month recruitment period. Primary study end points are the overall incidence rate of VA-related infections in ESRD patients on chronic HD (defined as infection episodes/100 patient-months), and the incidence rate of different types of VA-related infections (exit site, tunnel and bacteraemia/sepsis). All VA types in use will be evaluated: fistula, graft, tunneled (permanent) central venous catheter (CVC) and temporary CVC.