Post-transplantation Presentation of ANCA-associated Vasculitis: Granulomatosis with Polyangitis

Granulomatosis with polyangitis (GPA) is characterized by necrotizing granulomatosis of the upper and lower respiratory tract and glomerulonephritis. If GPA does not respond to appropriate management, it might result in end-stage renal disease, which may remit the disease severity. The overall impression is that immunosuppression following renal transplantation would further subside the vasculitis. However, several studies have shown that systemic vasculitis recur in 25% of patients following renal transplantation. This may indicate the perplexing nature of the immune system. One of the key factors in prevention of relapse of GPA is following up of patients by careful immunosuppressive dose adjustment and regular measurement of biomarkers for vasculitis. Herein, we describe an interesting case of biopsy-proven GPA who had a complex long history of several post-transplantation relapses in different organs with anti-neutrophil cytoplasmic antibodies seroconversion. This case emphasizes that vasculitis in particular GPA can mimic various diseases depending on which vessels and organs are affected by the inflammation and is one of the reversible causes of failure of transplanted kidney. Bearing the diagnosis in mind as one of the potential differential diagnoses of failure of renal transplantation will lead to early diagnosis and treatment of recurrent GPA.

Recurrent uric acid stones

A 46-year-old female had a history of recurrent uric acid stone formation, but the reason why uric acid precipitated in her urine was not obvious, because the rate of urate excretion was not high, urine volume was not low, and the pH in her 24-h urine was not low enough. In his discussion of the case, Professor McCance provided new insights into the pathophysiology of uric acid stone formation. He illustrated that measuring the pH in a 24-h urine might obscure the fact that the urine pH was low enough to cause uric acid to precipitate during most of the day. Because he found a low rate of excretion of NH(4)(+) relative to that of sulphate anions, as well as a high rate of citrate excretion, he speculated that the low urine pH would be due to a more alkaline pH in proximal convoluted tubule cells. He went on to suspect that there was a problem in our understanding of the function of renal medullary NH(3) shunt pathway, and he suggested that its major function might be to ensure a urine pH close to 6.0 throughout the day, to minimize the likelihood of forming uric acid kidney stones.

Anorexia nervosa and chronic renal insufficiency: a prescription for disaster

Our imaginary consultant, Professor McCance, is asked to explain the basis for four major acute electrolyte abnormalities in a young woman with long-standing anorexia nervosa. She has a severe degree of hypokalaemia (2.0 mmol/l) with renal potassium wasting, a contracted extracellular fluid volume with renal NaCl wasting, hyponatraemia (118 mmol/l) while excreting hypoosmolar urine, and metabolic acidosis with a normal plasma anion gap (pH 7.20, bicarbonate 9 mmol/l). McCance begins his discussion by considering the basis for hypokalaemia, as this electrolyte disorder is potentially life-threatening. Its pathophysiology is linked to the other major findings, using principles of integrative physiology together with a deductive and quantitative analysis. Nevertheless, to reach his final diagnosis, he requires information about newer molecular discoveries. Not only is he able to suggest a likely diagnosis, but he also devises a novel long-term plan for therapy.

A conceptual approach to the patient with metabolic acidosis. Application to a patient with diabetic ketoacidosis

We shall illustrate that management of patients with an acid-base disorder could be improved if the acid-base analysis was based on a better understanding of basic concepts of physiology. Three concepts of acid-base physiology and their clinical implications are emphasized in a patient with diabetic ketoacidosis. First, when an acid is produced from neutral precursors in the body, there is a net increase in the number of hydrogen ions (H(+)) and new anions. The corollary is that H(+) will be removed when the accompanying anion is metabolized to a neutral end-product or is excreted in the urine with H(+) or ammonium (NH(4)(+)). Second, buffering of H(+) is beneficial if H(+) are removed by bicarbonate rather than being able to bind to proteins. This latter function depends on having a low tissue PCO(2), due to a combination of hyperventilation plus an adequate blood flow rate to vital organs. Third, the kidneys add new bicarbonate to the body when NH(4)(+) is excreted with chloride ions.