5-nucleotidase and azathioprine-related bone-marrow toxicity

discontinued (she was on no other medication). Ham’s test negative, there was no evidence of viral infection, and bone marrow aspirate and trephine biopsy were hypocellular, confirming the diagnosis of severe aplastic anaemia. She was treated with rabbit antithymocyte globulin (ATG, Merieux) and is currently dependent on red cell and platelet transfusions. Her psychotic symptoms relapsed after remoxipride was stopped, but were partly responsive to treatment with trifluoperazine. The temporal relation between the development of aplastic anaemia and exposure to remoxipride and prothiaden in the first patient suggests that the aplasia was related to these agents. It is impossible to determine whether it was due to one drug alone or to the combination. In the second patient, remoxipride was the only drug administered; the time course of the illness is consistent with a diagnosis of drug-induced aplasia. Aplastic anaemia secondary to prothiaden treatment has been reported (11 cases were reported to the UK Committee for Safety of Medicines [CSM] up to May, 1993). There have been no previous reports of aplastic anaemia in relation to remoxipride although one case of leucopenia has been reported to the CSM. We suggest regular haematological monitoring of patients treated with remoxipride to delineate the potential risk was

was

of bone marrow failure. NJ Philpott, J C W Marsh, E C Gordon-Smith Department of Haematology, St George’s Hospital Medical School, London SW17 ORE, UK

J S Bolton Department of Psychiatry, St George’s Hospital

Medical School

SIR-In

September, 1993, a 43-year-old woman with longstanding schizophrenia was admitted to our unit with symptomatic anaemia and easy bruising. Subsequent investigations showed a peripheral pancytopenia with haemoglobin 4-8 g/dL, reticulocytes 0-1°,o, white cell count 2’7 x 109/L (neutrophils 1-5 x 109/L which subsequently fell to 0-02 x 109/L), and a platelet count of 1 x 109/L. Bone marrow trephine biopsy showed hypocellular appearances with no evidence of blasts, fibrosis or malignant disease, bone marrow cytogenetic studies showed 46 XX and a diagnosis of very severe aplastic anaemia was made. Serum B12 and folate levels were normal and there was no evidence of haemolysis. Auto-antibodfy screen was negative as was serology for hepatitis viruses, cytomegalovirus, and Epstein-Barr virus. There

of chemical or radiation exposure. Drug history included hormone replacement therapy (Prempak C), and occasional paracetamol and remoxipride hydrochloride which she had been taking as a single agent for the previous 7 months up to a dose of 600 mg daily for relapse of schizophrenia, refractory to sequential short courses of sulpiride and trifluoperazine. Since diagnosis, management has entailed withdrawal of all pre-existing drugs, supportive measures, and attempts at definitive treatment of the marrow aplasia with cyclosporin, initially, and subsequently, horse anti-lymphocyte globulin. To date there has been no response in terms of haematological was no

history

indices.

Although a coincidental finding of idiopathic aplastic anaemia in a patient on remoxipride hydrochloride is possible, the occurrence of drug-induced aplasia is also conceivable. We would suggest that prescribers of remoxipride hydrochloride maintain vigilance for potential haematological abnormalities. S T Laidlaw, J A Snowden, M J Brown Department of Haematology, Northern General Hospital NHS Trust, Sheffield 55 7AU, UK

5-nucleotidase and azathioprine-related bone-marrow toxicity SIR-Severe bone-marrow toxicity is a potentially lifethreatening side-effect of azathioprine. After conversion to 6-mercaptopurine, the metabolism of azathioprine parallels the endogenous purine pathways. Low activity of thiopurine methyltransferase (TPMT) is a cause of azathioprine-related bone-marrow toxicity.1-3 However, other mechanisms must be present too since normal TPMT activity is found in several patients with azathioprine-related leucopenia.4 Recently, we found very low lymphocyte 5-nucleotidase (5-NT) activityS in 3 patients with a history of azathioprine-related bone-marrow depression compared with 14 healthy controls. No abnormalities were detected in erythrocyte activity of TPMT66 and lymphocyte activities of purine nucleoside phosphorylase and hypoxanthine-guanine-phosphoribosyltransferase.5 Case 1 is a 50-year-old male renal transplant recipient. Immunosuppression initially consisted of cyclosporin and prednisone and was routinely changed to azathioprine 27 mg/kg daily and prednisone 10 mg daily after 3 months. Haematological parameters were essentially normal at the start of azathioprine. Within 3 weeks a slight decrease in white cell count (WCC), platelets, and haemoglobin (Hb) necessitated dosage reduction of azathioprine to 0-9 mg/kg. 1 week later, overt leucopenia (1 ’0 x 109/L) developed and azathioprine was withdrawn. A rechallenge was followed by pancytopenia within 3 weeks (WCC 05 x 109/L, platelets 48 x 109/L, Hb 3-1 mmol/L). Blood transfusions were given, and his WCC and platelet counts rapidly improved after azathioprine was withdrawn. Kidney function after transplantation was good and stable over time (endogenous creatinine clearance more than 50 mL/min). Lymphocyte activity of 5-NT was found to be low (2-46 nmol per 10-6 cells per hour vs controls: median 9-64, 75th percentile 13-16, 25th percentile 6-16, lowest value

3-75). Case 2 is a 57-year-old man with rheumatoid arthritis since 1972. Previous treatment consisted of aurothioglucose, D-

penicillamine, auranofin, and low-dose prednisone. Haematological parameters as well as kidney function were essentially normal when azathioprine 1-8 mg/kg daily was started. A fall in WCC occurred after 8 weeks, and despite gradual dosage reduction to 05 mg/kg per day, azathioprine had to be withdrawn 7 weeks later because of severe leucopenia (08 x 109/L). No changes in haemoglobin and platelet count had occurred. 5-NT activity was 2-49 nmol per 10-6 cells per hour. Case 3,

a

52-year-old male renal transplant recipient, had 4 leucopenia. 1 month after transplantation his

of

episodes endogenous creatinine clearance was 60 mL/min and immunosuppression was changed to azathioprine 24 mg/kg daily and prednisone 10 mg/day. 3 weeks later a rapid fall in WCC (1 -6 x 109/L) occurred and azathioprine was withdrawn. Within 10 days, his WCC returned to normal. A significant rise in cytomegalovirus IgG concentration, but not IgM, and a slight increase in transaminases were observed during this episode. 3 weeks after its discontinuation azathioprine was resumed. With dosage adjustments (varying between 0-6 and

mg/kg daily) the drug could be continued for 10 weeks. Leucopenia (2-0 x 109/L) occurred twice during this time: during a 3-week antithymocyte globulin course given for

2-4

presumed rejection, and when he received high-dose cotrimoxazole for Pneumocystis carinii pneumonia. A third challenge with azathioprine, 3 weeks after co-trimoxazole was stopped, was followed again by leucopenia (2-1 x 109/L). No alternative explanation was available, and azathioprine was stopped. Kidney function, haemoglobin, and platelet count remained constant during follow-up. 5-NT activity in this patient was very low (1 38 nmol per 10-6 cells per hour). 1245

Bone-marrow depression in cases 1 and 2 must be attributed to azathioprine. Although alternative explanations are available for 3 of 4 episodes in case 3, we believe that the fourth episode of leucopenia, in particular, demonstrates the relation with azathioprine. The formation of cytotoxic thionucleotides and their feedback inhibition on de-novo purine synthesis are held responsible for the therapeutic and adverse effects of purine analogues. Concurrent use of azathioprine and allopurinol, a xanthine-oxidase inhibitor, is a well-known cause of azathioprine-induced bone marrow toxicity. However, none of our patients used allopurinol at the time bone-marrow toxicity occurred, and the absence of decreased serum urate excludes the possibility of xanthine-oxidase deficiency as a cause of azathioprine toxicity. An excess of thionucleotides was found in TPMT-deficient patients with azathioprine-induced bone marrow toxicity. No TPMT deficiency was present in our patients. All 3 patients had very low 5-NT activity compared with controls. Like in TPMT deficiency, this may lead to higher amounts of thionucleotides causing increased susceptibility to bone marrow toxicity during azathioprine. Unfortunately we did not have the opportunity to measure thionucleotide. We suggest that, in addition to TPMT deficiency, low activity of 5-NT may be another cause of azathioprine-induced bone marrow toxicity. This study was rheumatism.

supported by

a

grant from the Dutch

League against

Pit J S M Kerstens, Jan N Stolk, Luuk B Hilbrands, Levinus B A van de Putte, Ronney A De Abreu, Agnes M T Boerbooms Departments of Rheumatology, Nephrology, and Paediatrics, University Hospital Nijmegen, PO Box 9101, 6500 HB Nijmegen, Netherlands

Lennard L, Van Loon JA, Weinshilboum RM. Pharmacogenetics of

1

azathioprine toxicity: relationship to thiopurine methyltransferase genetic polymorphism. Clin Pharmacol

acute

Ther 1989;

46: 149-54.

Chocair PR, Duley JA, Simmonds HA, Cameron JS. The importance of thiopurine methyltransferase activity for the use of azathioprine in transplant recipients. Transplantation 1992; 53: 1051-56. 3 Schütz E, Gummert J, Mohr F, Oellerich M. Azathioprine-induced myelosuppression in thiopurine methyltransferase deficient heart transplant recipient. Lancet 1993; 341: 436. 4 Soria-Royer C, Legendre C, Mircheva J, Premel S, Beaune P, Kreis

patients with typical symptoms receive empirical treatment, and diagnostic evaluation is reserved for patients with atypical or refractory symptoms,7 Ambulatory monitoring and provocative testing have not been directly compared in an atypical patient population. At the Mayo Clinic, we use a provocative pH study and ambulatory pH monitoring in clinical practice. The provocative test is shorter, can be combined with oesophageal manometry, and can be done even if a patient is on acid-suppressive therapy. We compared a provocative reflux study with ambulatory monitoring in patients with atypical or refractory symptoms. After providing informed consent, 13 patients (median age 39, range 18 to 62; 9 female) had a provocative reflux study (short study) and then prolonged ambulatory pH monitoring done consecutively. The indications for pH testing were heartburn refractory to therapy (6 patients), chest pain (2), chronic cough (2), Barrett’s oesophagus (1), epigastric burning (1), and possible hypersecretory state (1). Endoscopy was done on 9 patients before pH testing; none had oesophagitis. No patient had taken antisecretory therapy within 48 hours of the study. The study was approved by the institutional review board of the Mayo Clinic. For the short study, oesophageal pH was measured during 24 maneouvres: leg lifts, valsalva, deep sniffs, and abdominal compression each done three times before and after the instillation of 300 mL of 01 mmolJL hydrochloric acid. A positive study was defined as three or more manoeuvres resulting in a drop in pH below 4.8 Ambulatory monitoring was defined as positive if the total time with a pH less than 4 exceeded 4% or if the Johnson and DeMeester composite score exceeded 22.’’ 4 patients had positive short studies. 2 other patients had free reflux on the short study but did not have pH changes with manoeuvres. 6 patients had positive ambulatory pH

monitoring tests: Ambulatory monitoring

2

H.

5

6

Thiopurine-methyl-transferase activity to assess azathioprine myelotoxicity in renal transplant recipients. Lancet 1993; 341: 1593-94. Laarhoven JPRM, Spierenburg GT, de Bruyn CHHM. Enzymological analysis of purine metabolism in lymphoid cells. J Immunol Methods 1980; 39: 47-58. Weinshilboum RM, Raymond FA, Pazonino PA. Human erythrocyte thiopurine methyltransferase: radiochemical assay and biochemical properties. Clin Chim Acta 1978; 85: 323-33.

24-hour monitoring for gastro-oesophageal reflux disease SiR-Over the past 20 years, ambulatory oesophageal pH has become a part of the diagnostic evaluation of heartburn, chest pain, dysphagia, cough, asthma, globus sensation, and other complaints. The test has been used as the gold standard to assess the sensitivity and specificity of reflux symptoms,’ but there are concerns about its diagnostic accuracy. No consensus exists about the normal amount of acid reflux,2 and substantial variability has been documented when studies are repeated in the same subjects.3,4 Ambulatory monitoring has also not been able to predict response to therapy or complications,-5 and has been shown to be less reliable than stationary oesophageal pH monitoring,6 When first introduced, ambulatory pH monitoring was compared with short provocative pH tests in groups of patients with and without typical symptoms of reflux. In current practice,

monitoring

1246

The overall agreement was only 69% (the kappa statistic, which measures chance-corrected agreement, was 0-37). The 2 patients with free reflux in the short study had it repeated (outside the protocol) and the repeat study was positive in both patients. If these two are considered positive, the overall agreement was no better than chance. Which test is correct? When the two pH studies were discordant, the clinicians caring for the 4 patients treated according to the result of the short study in 2 and the ambulatory pH monitoring in 2 patients. Our data emphasises the need for studies that use response to therapy and long-term outcome to determine which diagnostic tests accurately define who in fact has gastro-oesophageal reflux disease. G Richard Locke, Nicholas J Talley Division of Gastroenterology and Internal Medicine, Rochester, MN 55905, USA

1 2

3

4 5

Mayo Clinic and Mayo Foundation,

Klauser AG, Schindlbeck NE, Müller-Lissner SA. Symptoms in gastro-oesophageal reflux disease. Lancet 1990; 335: 205-08. Quigley EMM. 24-h pH monitoring for gastroesophageal reflux disease: already standard but not yet gold? Am J Gastroenterol 1992; 87: 1071-74. Weiner GJ, Morgan TM, Cooper JB, et al. Ambulatory 24-hour esophageal pH monitoring: reproducibility and variability of pH parameters. Dig Dis Sci 1988; 33: 1127-33. Johnsson F, Joelsson B. Reproducibility of ambulatory oesophageal pH monitoring. Gut 1988; 29: 886-89. Olden K, Triadafilopoulos G. Failure of initial 24-hour esophageal pH monitoring to predict refractoriness and intractability in reflux

esophagitis. Am J Gastroenterol 1991; 86:

1142-46.

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