1 Departments of Nephrology and 2 Pathology, Chang Gung Memorial Hospital, Taipei, Taiwan
Correspondence and offprint requests to: Dr Hong Jenn-Jye, Department of Nephrology, Chang Gung Memorial Hospital, 5, Fu Hsing Street, Kuei-Shan Hsian, Taoyuan, Taiwan.
Keywords: Escherichia coli; haemolyticuraemic syndrome; malakoplakia; urinary tract infection
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Introduction |
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As reported in the literature, the usual presentation of renal parenchymal malakoplakia (RPM) is that of urinary tract infection, pyelonephritis, and unilateral enlarged kidney [2]. Acute renal failure was also reported in some cases, but most associated with volume depletion, septic syndrome, urinary tract obstruction or other active systemic disease [24].
We report an atypical case of bilateral RPM that initially presented as urinary tract infection complicated with microangiopathic haemolytic anaemia, thrombocytopenia, and rapidly progressive renal failure which was compatible with the diagnosis of haemolyticuraemic syndrome (HUS) in an alcoholic woman.
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Case |
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On admission, the physical examination revealed a pale and ill-looking patient with body temperature 36°C, blood pressure 122/83 mmHg, respiratory rate 19 breaths/min, and pulse rate 97 b.p.m. The lungs were symmetric expanded and clear to auscultation bilaterally. Cardiovascular examination revealed a grade 2/6 ejection systolic murmur along the left sternal border. Abdominal examination was normal except bilateral flank pain on percussion. There was no peripheral oedema and palpable mass or lymphadenopathy. Rectal, genital, and neurological examinations were normal.
On admission, haemoglobin level was 4.1 g/dl, white blood cells 11 900/mm3 (95% neutrophils, 5% monocytes), platelets 117 000/mm3. The serum creatinine was 5.8 mg/dl, AST 56 U/l, and total bilirubin 2.1 mg/dl. Urinalysis showed 75 mg/dl proteinuria with sediment of 46 RBC, 5055 WBC per high-power field. The chest radiography was irrelevant and KUB revealed bilateral enlarged renal shadows. The renal ultrasonographic study showed bilateral large kidneys of 15 cm in length, but no other abnormalities.
The patient received a blood transfusion and was started on cefamezin and gentamicin. Subsequently, blood and urine cultures came back positive for Escherichia coli sensitive to ceftizoxime and gentamicin. Therefore antibiotics were changed according to the sensitivity test. Over the next few days the patient became more dyspnoeic. Haemoglobin was 5.5 g/dl with reticulocyte 1.5%, platelets 83 000/mm3. The BUN was 247 mg/dl, creatinine 9.6 mg/dl, uric acid 16.2 mg/dl, calcium 7.9 mg/dl and phosphorus 12.6 mg/dl, sodium 133 mmol/l and potassium 7.0 mmol/l. Peripheral blood smear revealed marked polychromasia, schistocytes, nucleated and fragmented RBC. These findings are compatible with intravascular haemolysis (Figure 1). The direct and indirect Coombs' test were negative. The complement level, antinuclear antibody, immunoelectrophoresis, protein electrophoresis and DIC profiles were all within normal limits. The clinical picture of microangiopathic haemolytic anaemia, thrombocytopenia, and acute worsening renal function were compatible with the diagnosis of haemolyticuraemic syndrome. On the same day, emergency haemodialysis was performed via right femoral vein dual catheter. However, frequent blood transfusions and intensive haemodialysis failed to improve the clinical status of the patient and patient remained dyspnoeic and severely anaemic (haemoglobin: 2.2 g/dl). On day 17, plasma exchange and intravenous steroid therapy (5 mg/kg/day, solucortef) was commenced. Gradually her haematological indices improved, and then plasma exchange and steroid therapy were discontinued. The clinical course is summarized in Figure 2
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Discussion |
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The pathogenesis of malakoplakia is unknown. Gram-negative enteric bacilli, mainly E. coli as our case, have been implicated. Most authors agree that there is a diminished capacity of macrophages for lysis of bacteria due to a decreased intracellular cGMP/cAMP ratio [1]; explaining the formation of intracellular bacterial inclusions called Michaelis Gutmann bodies, and the presence of large histiocytes called Von Hansemann cells.
Malakoplakia usually affects the collecting system of the urinary tract, although involvement of other organs has been reported [14]. Renal parenchymal malakoplakia (RPM) is relatively rare. A search of the MEDLINE database and review of bibliographic references contained in articles on malakoplakia, revealed only 43 cases of RPM that had been published over the past 20 years, and 14 were bilateral [6]. The case we report herein is, to our knowledge, the first in that the initial presentation of bilateral RPM mimics haemolyticuraemic syndrome (HUS). The clinical presentation, i.e. an alcoholic woman with urinary tract infection caused by E. coli, renal failure, and bilateral enlarged kidney, was similar to what has been described in the literature. The association of severe intravascular haemolytic anaemia, thrombocytopenia, and rapidly progressive renal failure requiring haemodialysis that are compatible with the diagnosis of HUS is unique, however. This unusual presentation of bilateral RPM had rendered diagnosis difficult.
Escherichia coli infection is well known to play a significant role in the pathogenesis of HUS [7,8], which is most often caused by verotoxin-producing serotype such as E. coli O157. This toxin is believed to induce endothelial damage in the small blood vessels supplying the kidney and various organs, thus giving rise the signs and symptoms that characterize HUS. Clinically, this group is usually associated with a diarrhoea prodrome [8]. Our patient experienced no diarrhoeal prodrome. Blood and urine isolates at the beginning of the illness were also negative for the production of verotoxin by tissue culture cells and are therefore apparently not responsible for the development of HUS. However, the phenotype of cultured cells (HeLa or Vero) used for the verotoxin assay may change with time and become less sensitive to toxin [9]. Besides, there exists non-diarrhoeal form of HUS that may be familial or associated with a variety of infectious agents or drugs; it is generally unrelated to verotoxin-producing bacterial infection [7,9]. Our patient had no history of drug use or of systemic disorders that may trigger HUS. Therefore we cannot exclude an association with E. coli urinary tract infection.
Treatment of RPM must focus on improving the state of immunodeficiency [2,10] and on administration of antibiotics, especially of antibiotics with high intracellular diffusion and activity. Urecholine, a cholinergic agonist, had been shown to improve the bactericidal activity of monocyte against E. coli in an adult with rectal malakoplakia [11]. When there is poor response to medical therapy, the surgical drainage of renal abscesses or nephrectomy is mandatory [3].
Although detailed investigation of the immune system was not carried out, we believe that this patient's severe debilitating alcoholism may have interfered with her response to infection and resulted in the development of RPM. In conclusion, renal parenchymal malakoplakia should always be taken into account in the differential diagnosis of a patient who presents with urinary tract infection, enlarged kidneys, and acute renal failure, especially if this concerns an immunocompromised alcoholic.
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References |
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