Acquired renal glucosuria in an undifferentiated connective tissue disease patient with a SLC5A2 heterozygous mutation: A case report.

INTRODUCTION: Renal glucosuria is a renal tubular disorder caused by genetic conditions, drugs, and poisons. Mutations in the SLC5A2 gene are recently found to be responsible for the inherited renal glucosuria, while undifferentiated connective tissue disease (UCTD) was not considered pathogenic for renal glucosuria. Here, we present a case of acquired renal glucosuria in a UCTD patient. PATIENT CONCERNS: A 30-year-old woman was seen in the outpatient clinic for complaints of frequent urination and dysuria. Laboratory tests showed a urinary tract infection (UTI) and persistent renal glucosuria. After antibiotic treatment, the UTI symptoms were relieved, but the renal glucosuria remained. DIAGNOSIS: Laboratory tests ruled out renal tubular acidosis and diabetes mellitus. Genetic analysis showed a heterozygous mutations in the SLC5A2 gene. Meanwhile, immunological tests showed a high antinuclear antibody titer (1:160) and an elevated anti-Rho/SSA antibody level. Schirmer test, tear breakup time, and lip biopsy results were all negative. The patient did not meet the criteria for any known connective diseases. Therefore, she was diagnosed with UCTD. INTERVENTIONS: The patient was started with the treatment of Hydroxychloroquine. OUTCOMES: Hydroxychloroquine treatment resolved the renal glucosuria. The patient's follow- up urinalysis showed no glucosuria at all. LESSONS: This is the first case report to demonstrate that UCTD may induce renal glucosuria in a patient with a heterozygous mutation in SLC5A2. This case suggests that during the process of diagnosing renal glucosuria, in addition to familial renal glucosuria (FRG), autoimmune diseases, though rare, should also be taken into consideration.

[Renal glucosuria]. / Glucosurie rénale.

The occurrence of glucosuria in the absence of hyperglycemia is distinctive for renal glucosuria. SGLT2 mutations provoke familial renal glucosuria characterized by persistent glucosuria in the absence of any other renal tubular dysfunction. Renal glucosuria associated with others proximal tubular dysfunctions points to Fanconi syndrome. This generalized dysfunction of proximal tubule needs to be treated and may progress regarding its aetiology to chronic renal failure. The development and study of models of Fanconi syndrome has recently contributed to a better knowledge of the mechanisms implicated in the tubular transport of glucose and low-molecular-weight-proteins. This article reviews these recent developments.

Reversible renal glycosuria in acute interstitial nephritis.

Renal glycosuria is defined as the excretion of glucose in urine in a normoglycemic state. It results from renal tubular dysfunction or immaturity of tubular function in the newborn. Etiologically, renal glycosuria is of 3 types-benign renal glycosuria, glycosuria with diabetes mellitus (including gestational diabetes) and tubular defects (Fanconi syndrome). Prognosis of benign renal glycosuria is excellent and reversible. Acute interstitial nephritis (AIN) is one of the main causes of acute renal failure and may often result in tubular dysfunction. In this study, the authors report the occurrence of AIN with acute renal failure that contributed to reversible renal glycosuria. The glycosuria observed in the patient of this study was an isolated tubular defect, with no phosphaturia, aminoaciduria or bicarbonaturia. Such a presentation is very rare in adults and has not been previously reported. These findings confirm that AIN with acute renal failure can cause an isolated tubular defect with benign reversible glycosuria in an adult.

Renal tubular function in children with beta-thalassemia minor.

BACKGROUND: beta-thalassemia minor is a common heterozygous haemoglobinopathy that is characterized by both microcytosis and hypochromia. It requires no treatment. It has been postulated that low-grade haemolysis, tubular iron deposition and toxins derived from erythrocytes might cause renal tubular damage in adult patients with beta-thalassemia minor. Our aim was to investigate the renal tubular functions in children with beta-thalassemia minor and to determine its possible harmful effects. METHODS: The study was conducted on 32 children (14 female and 18 male) at the age of 5.8 +/- 3.1 years (range 2-14 years) with beta-thalassemia minor. The patients were classified as anaemic (haemoglobin (Hb) 11 g/dL) (Group 2, n = 18). A control group was formed with 18 healthy children whose ages and sexes match those in other groups (Group 3, n = 18). Fractional excretion of sodium (FE(Na), %), fractional excretion of magnesium (FE(Mg), %), fractional excretion of uric acid (FE(UA), %) and tubular phosphorus reabsorption (TPR,%) were calculated with standard formulas. Urinary calcium excretion (mg/kg per 24 h), zinc (Zn) (microg/dL), glucosuria (mg/dL), beta-2 microglobulin (mg/dL) and N-acetyl-beta-D-glycosaminidase (NAG, U/mmol creatinine) levels were measured through biochemical methods. RESULTS: There was no statistically significant difference among the three groups in terms of the results of FE(Na) (%), FE(Mg) (%), FE(UA) (%), TPR (%), calciuria (mg/kg per 24 h), NAG, urine Zn, proteinuria, glucosuria or urine beta- 2 microglobulin levels (P > 0.05). CONCLUSION: On the contrary of children with beta-thalassemia major, renal tubular dysfunction has not been determined in children with beta-thalassemia minor in the present study.

Transient renal glycosuria in a patient with acute pyelonephritis.

Glycosuria was detected in a 37-year-old Chinese woman by a urinary examination in a local clinic with clinical evidence of acute pyelonephritis (APN). Transient glycosuria is an unusual complication of acute pyelonephritis in non-diabetic patients. As there is growing prevalence of type 2 diabetes in the population worldwide, it must be recognized that mistaken diagnosis of diabetes mellitus by glycosuria may predispose patients to an unfavorable hypoglycemic episode. Thus definite diagnosis of diabetes mellitus should be made only after recovery of APN by means of urinalysis or by simultaneous blood glucose concentration analysis.

[Renal glucosuria and membranous glomerulonephritis in chronic inflammatory demyelinating polyradiculoneuropathy: CIDP].

Glucosuria was detected in a 7-year-old boy by a routine school mass examination in April 1991. The diagnosis of renal glucosuria was made in the affiliated hospital of the University of Tsukuba. The patient developed muscle weakness and gait disturbance in February 1993. Spinal fluid examination revealed a protein level of 62 mg/dl and a cell count of 4/3. Under the diagnosis of Guillain-Barré syndrome, he was treated with i.v. immunoglobulin and oral prednisolone. Although the therapy somewhat improved the symptoms, his muscle strength had not fully recovered at the end of the treatment. In November 1995, the muscle weakness became worse; he could not go up stairs, nor stand upright on one leg. In April 1996, proteinuria was detected in a school mass examination. He was referred to the University Hospital of Tsukuba for a full renal study in March 1997. Renal biopsy revealed global sclerosis in 16 of 19 glomeruli with extensive interstitial fibrosis and mononuclear cell infiltration. A diagnosis of membranous glomerulonephritis was established based on the findings of spikes in PASM staining, weak IgG deposition in the glomerular capillary and subepithelial deposits by electron microscopic study. Additionally, pituitary growth hormone deficiency was found by endocrinological examination. The diagnosis of CIDP was established by fibulal neuron biopsy, which revealed neuronal degeneration and profound demyelinization. The clinical course of the present case was unlike that of the few reported cases of MGN associated with CIDP described in the literature. The initial renal symptom was glucosuria, which started 5 years prior to the onset of proteinuria. Second, glomerulosclerosis was more extensive than that seen in the literature. We surmise that chronic interstitial nephritis of insidious onset was followed by MGN which developed subsequently, probably at the time of the start of proteinuria.

Transient renal glucosuria in patients with tetanus.

BACKGROUND/AIMS: During our early years of experience with patients suffering from tetanus, some of them were found to have unexplained renal glucosuria. METHODS: Thus, all the normoglycemic patients with tetanus who were consecutively encountered over the subsequent 8 years were studied for the presence of renal glucosuria. RESULTS: From 92 cases of tetanus admitted to the intensive-care unit, 63 patients had normal blood sugar in the course of their illness. The quantitative measurement of 24-hour urine confirmed the presence of significant renal glucosuria in 52% (n = 33) of these cases. The renal glucosuria was of transient nature and decreased to normal levels in the recovery stage (4 weeks after discharge from the hospital). There was no significant difference in age, sex, severity of disease and site of entry between the two groups of the patients with and without renal glucosuria. CONCLUSION: Significant but transient glucosuria of renal origin possibly induced by tetanospasmin is common in patients with tetanus.

Hyperoxaluria with hyperglycoluria not due to alanine:glyoxylate aminotransferase defect: a novel type of primary hyperoxaluria.

Considering the clinical heterogeneity of primary hyperoxaluria type I (PH1) and the fact that in many instances this diagnosis was made without enzymatic and immunohistochemical investigation, other disturbances of oxalate metabolism than those presently known can be expected in PH1. Using a gaschromatographic/mass spectrometric method that allows quantification of these acids, hyperoxaluria and hyperglycoluria was found repeatedly in two unrelated patients. The hyperoxaluria was unresponsive to pyridoxine. There was no nephrocalcinosis or urolithiasis. In the liver biopsy normal AGT activity and normal localization of this enzyme in the peroxisome was found. In one patient abnormal Km and maximal activity and mozaicism of AGT were excluded. Hyperoxaluria and hyperglycoluria were also found in other family members, suggesting autosomal dominant transmission. Although the underlying defect leading to hyperoxaluria and hyperglycoluria could not be identified in these patients, it is probable that they represent a separate type of primary hyperoxaluria.

Renal glycosuria in renal homograft recipients.

Transient renal glycosuria was observed in eight renal transplant patients during the recovery phase from initial tubular necrosis or acute rejection. In these subjects and three homograft recipients without glycosuria we performed glucose titration experiments. Three patients were found to have type A glycosuria, two had type B and three type C. The titration curve was normal in the three patients without glycosuria. In addition, most subjects presented with hypophosphataemia and hyperphosphaturia. Apart from a direct correlation between the point of splay of the glucose titration curves and the fractional clearance of phosphate, there was no clear-cut relationship between the handling of glucose and phosphorus. Mild hyperchloraemic acidosis was observed in six subjects, but this was unrelated to the type and grade of glycosuria. It is concluded that in homograft recipients the tubular alterations have a patchy and unpredictable distribution and may cause a variety of symptoms which do not necessarily occur in close association.

Renal glycosuria in patients with the nephrotic syndrome.

Transient or persistent renal glycosuria may occur in patients with the nephrotic syndrome. In an attempt to elucidate its mechanism, glucose titration experiments were performed in 20 nephrotic patients. The type A titration curve was found in one and type B in four patients with severe organic changes and low glomerular filtration rate. The remaining subjects displayed a particular type of curve (type C) characterized by a low point of splay but an otherwise almost physiological tracing. In type B and C patients the maximal rate of reabsorption per ml glomerular filtrate (TmG/GFR) was significantly increased and correlated inversely with the filtration fraction. In these patients the point of splay correlated with the glomerular filtration rate and the sodium clearance, but not with the plasma albumin concentration or the rate of proteinuria. These observations suggest that type A was due to diffuse tubular atrophy, and type B to increased nephron heterogeneity resulting from chronic organic changes. Type C was presumably caused by a potentially reversible alteration of the late proximal or distal glucose transport related to the nephrotic syndrome itself.

Nephrotic syndrome and multiple tubular defects in children: an early sign of focal segmental glomerulosclerosis.

The nephrotic syndrome is rarely associated with renal tubular defects, and the combination has been reported only in association with advanced renal insufficiency. We report here five children with nephrotic syndrome and multiple tubular defects which evolved when glomular filtration rate ranged between 56 and 90 ml/minute/1.73 m2. The tubular defects were first noted at 3, 4, 4, 7, and 22 months after the onset of the nephrotic syndrome, and renal glycosuria was the first sign in all five children. Glycosuria was intermittent in three patients, constant in two, and ceased with loss of kidney function. Four patients had hyperaminoaciduria and renal tubular acidosis (two of four tested had distal renal tubular acidosis). Three patients had decreased tubular reabsorption of phosphorus and defective maximum concentrating capacity. All five had focal segmental glomerulosclerosis proven by renal biopsy. Over a follow-up period of seven years, all of the children have developed advanced renal insufficiency, four of the five have required dialysis or transplantation within 21 to 72 months after onset, and one has stabilized renal function at 35 ml/minute/1.73 m2. The one patient receiving a kidney transplant has had recurrence of focal segmental glomerulosclerosis in the transplanted kidney and became nephrotic with three subsequent transplants. Our experience suggests that the nephrotic syndrome associated with tubular defects in children forms a subgroup of focal segmental glomerulosclerosis, with rapid progression to renal insufficiency and the potential for recurrence of the lesion in the transplanted kidney.

Metabolic disorders in acute myeloid leukaemia.

Metabolic balance studies were carried out in 17 unselected patients with acute myeloid leukaemia. Widespread metabolic disturbances were observed. Serum Na fell below 135 mmol/1 in 14 patients (82%) and 11 patients (64%) developed hypokalaemia. An increased osmolal clearance caused by a release of electrolyte and blast cell waste (i.e. urea, urate, etc.) during chemotherapy appeared to be the principle cause of natriuresis and hyperkaluria. Seven patients had proteinuria before and eight others developed it during antileukemic therapy. Nine patients (53%) developed proximal renal tubular dysfunction with aminoaciduria, hyperphosphaturia and incomplete reabsorption of urate. No significant relation was found between this widespread glomerulo-tubular dysfunction and lysozymuria. We suggest that antileukaemic drugs release unidentified substances from blast cells which are toxic to the kidney. Metabolic alkalosis in six patients (35%) was probably related to volume depletion and hypokalaemia, while two patients developed acidaemia with the onset of renal failure. Hypocalcemia in seven patients (41%) had a multifactorial basis: hyperphosphaturia, septicaemia, malnutrition and cytotoxic drugs were among the probable causes.