Case Report: Azathioprine: An Old and Wronged Immunosuppressant

Mycophenolate rapidly substituted azathioprine (AZA) in transplant immunosuppression regimens since the 1990s, when early clinical trials indicated better outcomes, although opposite results were also observed. However, none of these trials used the well-established optimization methods for AZA dosing, namely, thiopurine methyltransferase pharmacogenetics combined with monitoring of the thiopurine metabolites 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP). Resistance to optimize AZA therapy remains today in transplant therapy, despite the fact that thiopurine metabolite testing is being used by other medical disciplines with evident improvement in clinical results. In a previous analysis, we found that active 6-TGN metabolites were not detectable in about 30% of kidney transplant patients under continuous use of apparently adequate azathioprine dosage, which demonstrates the need to monitor these metabolites for therapeutic optimization. Two of four case studies presented here exemplifies this fact. On the other hand, some patients have toxic 6-TGN levels with a theoretically appropriate dose, as seen in the other two case studies in this presentation, constituting one more important reason to monitor the AZA dose administered by its metabolites. This analysis is not intended to prove the superiority of one immunosuppressant over another, but to draw attention to a fact: there are thousands of patients around the world receiving an inadequate dose of azathioprine and, therefore, with inappropriate immunosuppression. This report is also intended to draw attention, to clinicians using thiopurines, that allopurinol co-therapy with AZA is a useful therapeutic pathway for those patients who do not adequately form active thioguanine metabolites.

COVID-19 and Cytomegalovirus Co-infection: A Challenging Case of a Critically Ill Patient with Gastrointestinal Symptoms

COVID-19 is a severe disease that has reached pandemic status. To the best of our knowledge, we describe the first case of COVID-19 and cytomegalovirus (CMV) co-infection in a critically ill patient. We discuss the challenge of establishing the diagnosis as well as the management of tissue-invasive gastrointestinal CMV infection (TI-GI CMV) simulating vascular involvement and intestinal obstruction in a critically ill patient.

LEARNING POINTS

We describe a case of COVID-19 and cytomegalovirus (CMV) co-infection in a critically ill patient.Clinical symptoms simulated mesenteric vascular involvement and intestinal obstruction.The successful management of invasive CMV colitis in a patient with COVID-19 with atypical symptoms is described.

Transplantation of horseshoe kidney en bloc

Horseshoe kidney is probably the most common renal fusion anomaly. With the continuous donor shortage, transplant surgeons tend to accept donors previously considered unsuitable. We present a successful case of en bloc horseshoe kidney transplant in a single recipient. The literature is reviewed. The use of horseshoe kidneys in transplantation is recommended in selected cases.

[Comparison of clinical and histological diagnosis in kidney post-transplantation period]

PURPOSE

To assess the agreement between clinical and histopathological diagnosis in a renal transplantation center, 40 episodes of acute renal failure were studied.

METHODS

Kidney biopsies were performed at the moment that a clinical diagnosis was made by the staff.

RESULTS

Nineteen episodes of acute tubular necrosis (ATN), eighteen episodes of acute cellular rejection (ACR), 2 humoral rejections and 1 acute cyclosporin nephrotoxicity episodes were diagnosed. ATN episodes were confirmed by renal biopsy in 84.21%, ACR episodes in 83.33%, humoral rejections in 100%. Renal biopsy showed ATN in the occurrence of clinical cyclosporin nephrotoxicity. Total agreement was 82.5%.

CONCLUSION

There is a good relationship between clinical and histopathological diagnosis in the post-transplantation period. Diagnostic mistakes occurred mainly when oliguria was present.

Renal transplantation using external continent urinary diversion

A 29-year-old man born with bladder exstrophy presented with end stage renal failure many years after ileal conduit diversion. Bilateral nephrectomy and continent external urinary diversion were performed, and 1.5 months later a cadaveric kidney was grafted into the right iliac fossa. The patient was well at 18 months with a serum creatinine level of 1.2 mg./dl. and he was completely dry with 4 or 5 daily catheterizations. Although followup is still short, renal transplantation with drainage into an external continent urinary diversion permits excellent quality of life and good renal function. Therefore, this alternative is worth consideration whenever other reconstructive alternatives are not possible in candidates for renal transplantation.

Fast and slow methylators: do racial differences influence risk of allograft rejection?

A catabolic route for azathioprine involving methylation by thiopurine methyltransferase has been directly implicated in the drug's immunosuppressive efficacy. Since ethnic differences in thiopurine methyltransferase activity have been reported in a study of Lapps, this study compared the distribution of thiopurine methyltransferase activity in erythrocyte lysates from 134 healthy, randomly selected subjects living in Brazil, comprising 39 blacks (i.e. Afro-Brazilians), 33 white subjects, 30 mixed-race subjects, and 32 Brazilian-residing Japanese subjects. The results demonstrated bimodality of thiopurine methyltransferase activity compatible with genetic polymorphism in the white, black and mixed-race groups, but not in the Japanese, who were homogeneously 'fast methylators' (high thiopurine methyltransferase activity). Thiopurine methyltransferase activity was generally higher in Brazilian males than females, and some individuals in the black and mixed-race groups had very high activity. Azathioprine-immunosuppressed transplant patients with thiopurine methyltransferase activity above 35 pmol/h/mgHb have previously been shown to have significantly poorer outcomes. Using this thiopurine methyltransferase value as the cut-off point between 'poor responders' and 'good responders' to azathioprine, 65% of the Japanese, 59% of the black subjects, and 63% of the mixed-race subjects fell into the 'poor responder' category, compared with only 42% of the white group. Interestingly, this approximately 20% difference in azathioprine response corresponds to the racial differences seen in allograft survival.

[The influence of socio-economic conditions in renal posttransplant infection]

Two hundred and four patients who underwent renal transplantation were followed up as outpatients with a minimum of four years. They were divided into two socio-economic levels: group I - 104 patients who underwent transplantation in a private hospital and 120 patients (group II) with a lower socio-economic standard, treated in a public hospital. In both groups urinary infections and hepatitis were excluded. The incidence of infection in group I was 24% and in group II, 50% (p = 0.0002). There was no difference in relation to viral infection in either groups. However, bacterial infection and infection by opportunistic agents were significantly higher in group II (p = 0.0001 and p = 0.0282). The number of hospitalizations and the number of infections of patients were higher in group II. There was a tendency for an increase in mortality owing to infection in group II. There was no difference in the two groups as the parameters of: age, sex, type of donor, primary disease, number of rejections crises, level of serum creatinine and number of patients with ciclosporine. On the other hand, the dose of azathioprine and prednisone was mildly higher in those patients of group II. Low level of socio-economic conditions is a risk factor in renal transplant patients.

The importance of thiopurine methyltransferase activity for the use of azathioprine in transplant recipients

The immunosuppressive efficacy of azathioprine is related to its rapid metabolism in vivo to 6-mercaptopurine (6MP), with subsequent conversion to thioguanine nucleotides by an anabolic route involving hypoxanthine-guanine phosphoribosyltransferase. Two alternative catabolic routes exist: oxidation to 6-thiouric acid via xanthine oxidase and methylation to 6-methylmercaptopurine via the enzyme thiopurine methyltransferase (TPMT). Catabolism via either route would restrict formation of the active metabolites. We analyzed TPMT activity in erythrocyte lysates of 25 controls, 25 uremic patients on dialysis, and 68 transplanted patients. Median activity was lower in controls (31.0 pmol/hr/mg Hb, range 16.2-43.0) and transplanted patients receiving only cyclosporine and prednisolone (31.7 pmol/hr/mg Hb, range 12.7-43.5) than in the azathioprine treated group, (36.1 pmol/hr/mg Hb, range 16.1-71.3), or the uremic group on dialysis, (35.5 pmol/hr/mg Hb, range 18.6-62.6) suggesting that both azathioprine and uremia induce the enzyme, but CsA does not. Only 3 patients demonstrated total intolerance to azathioprine, 2 of whom had very low TPMT activity (zero and 12.7 pmol/hr/mg Hb). The intolerance of the third patient, despite high TPMT activity, was attributed to concomitant cotrimoxazole therapy. Patients with intermediate activity (15-26 pmol/hr/mg Hb) could tolerate azathioprine well. Of 29 cadaver recipients given only azathioprine plus prednisolone, 24 with a better clinical outcome had a significantly lower activity (33.1 pmol/hr/mg Hb, range 16.1-46.1) than 5 with reduced allograft function (42.5 pmol/hr/mg Hb, range 33.8-51.5). TPMT activity in these 24 patients was also significantly lower than the general group of azathioprine-treated recipients. This inverse association between TPMT activity and allograft function was again found among 30 patients receiving triple therapy (azathioprine, CsA, prednisolone). Self-selection of the best recipients for azathioprine immunosuppression apparently occurred, based on low catabolism of the drug. We conclude that total intolerance to azathioprine is rare and usually appears in patients with very low TPMT activities. Our results also suggest that the wide range of TPMT activity may be an important factor in determining long-term graft survival in azathioprine-treated patients; those with high activity might benefit from doses near the upper limit generally recommended.

[Cyclosporin A: experience of the Renal Transplant Unit of the Clinical Hospital of the Medical College of the University of Sao Paulo]

The authors report their experience using cyclosporine-A (CsA) in renal transplant patients. When compared with azathioprine/prednisone, CsA contributed significantly to a better graft and patient survival, either if used associated with prednisone of with azathioprine plus prednisone. CsA was also used in substitution to azathioprine in patients with hepatopathy attributed to azathioprine toxicity. The initial results are promising. The association of CsA and azathioprine with corticosteroids withdrawal was used as an attempt to allow normal growth in children. This seems to be the best choice of treatment for children. Careful monitoring of CsA blood levels avoids, or at least, minimizes nephrotoxicity. To achieve therapeutic CsA levels, patients with liver damage need lower, while children need higher oral CsA doses. To summarise: when CsA in carefully used, it is an excellent immunosuppressive drug.

[Recurrence of segmental and focal glomerulosclerosis in transplanted kidneys]

The course of 16 patients with segmental and focal glomerulosclerosis (SFGS) with kidney transplantation is reported. Ten out of 16 (group I) had the diagnosis histologically confirmed in their native kidneys. In 6 (group II) the diagnosis was suggested by the early development of SFGS in the graft and was considered a recurrence of the baseline disease. The recurrence (in group I) was 40% and the main clinical parameter was proteinuria, in nephrotic level, with early development in all cases (less than 60 days). In those patients who had an early development of the baseline disease (less than 4 years) the recurrence was greater, observed in 5 out of 8 grafts with 3 grafts lost due to the recurrence of focal glomerulosclerosis. On the other hand, the patients whose baseline disease had a longer period of development presented a better course of the recurrent glomerulosclerosis and no grafts were lost in this cases. We believe that renal transplantation of a live donor must be avoided in those patients with quick developing SFGS.

[Pregnancy in patients with renal transplantation]

From 1969 to 1987, 35 pregnancies occurred in 31 women with renal transplant. Four of them were still pregnant when this study was concluded. There was one ectopic pregnancy. All patients received azathioprine and prednisone. In the majority of patients the glomerular filtration rate increased in a way similar to normal pregnant women. In five cases there was a progressive loss in renal function. In four of them this was attributed to preexistent renal damage. No toxemia occurred. Anemia developed during 11 pregnancies and blood transfusion was required for five women. Four patients had urinary tract infection which was easily controlled with antibiotics. One patient had severe arterial hypertension, secondary to chronic rejection. One patient developed jaundice reverted with reduction in azathioprine doses. One woman died of septicemia secondary to fetal death, during the 6th month of pregnancy. Twenty children were born with no abnormalities, although many of them were underweighted. Two thirds of pregnancies were delivered by cesarean section. No harm to the pelvic allograft occurred in vaginal deliveries. There have been 4 abortions (2 of them were induced with no medical indication). Four pregnancies (26 to 39 gestational weeks) ended in stillborn babies: the mothers had impaired renal function associated with hypertension and proteinuria. One newborn died of pulmonary infection two days after delivery. Another was born with microcephaly and polydactilia and survived 6 years. No breast feeding was allowed.

Tuberculosis in patients with chronic renal failure

Nine cases of tuberculosis (TB) were diagnosed among 800 uremic patients, followed-up during 11 years, a prevalence of 1125%, 2.5 times higher than that in the general population. Six patients (66.7%) had lymph node involvement (4 cervical and 2 mediastinal). Three patients (33.3%) had pulmonary involvement (2 pleuro-pulmonary and 1 bilateral apical pulmonary). Eight patients were undergoing dialysis and 1 was pre-dialytic. The duration of dialysis ranged from 1 to 60 months. Three patients had previously received immunosuppressive drugs for unsuccessful renal transplantation. Daily fever was present in all but one patient; he was asymptomatic and TB was suspected after routine chest radiography. Biopsy was the diagnostic procedure in 7 patients (77.8%), four by direct cervical lymph node biopsy, 2 by mediastinal, performed by mediastinoscopy and 1 by pleural biopsy. In 2 other patients TB was confirmed by the presence of tubercle bacilli; in sputum (1 patient) and in a bronchial flushing specimen (the other patient). Triple therapy was used in all patients (isoniazid and ethambutol in all), plus rifampicin in 8 and streptomycin in 1. One patient had jaundice and another had optical neuritis. Five patients were cured. The other four died during treatment of causes unrelated to TB or its treatment.

Polycythemia after kidney transplantation: influence of the native kidneys on the production of hemoglobin

3 patients with renal transplantation who developed polycythemia presented normalization of the hemoglobin levels immediately after nephrectomy of the native kidneys. This observation induced the authors to study the role of the native kidneys in the genesis of polycythemia in recipients of renal allografts. Comparison was made among 32 patients submitted to renal transplantation, with maintenance of native kidneys (group I) and among 31 under the same conditions, but without the native kidneys (group II). Both groups were comparable according to age, sex, rejection crisis incidence and immunosuppressive therapy. It was observed that the hemoglobin levels of group I were significantly higher (p less than 0.05 to p less than 0.005) than those observed in group II, from the 3rd to the 30th posttransplantation month, becoming comparable from the 36th to the 54th months. The hemoglobin production, measured by the kinetics of labeled iron (59Fe), was higher in patients of group I. The authors concluded that the native kidneys are responsible for the observed polycythemia after a kidney transplantation.