High-dose dexamethasone for splenectomy in patients with idiopathic thrombocytopenic purpura.

High-dose intravenous immune globulin (IV IgG) is currently the treatment of choice for patients with idiopathic thrombocytopenic purpura (ITP) who undergo splenectomy; however, this treatment is extremely expensive. We report on 13 ITP patients with severe thrombocytopenia (<20 x 10(9)/l) who were prepared for laparoscopic splenectomy with a 4-day oral course of high-dose (40 mg/day) dexamethasone (DEX). Four patients had an excellent response with platelet counts that increased to above 150 x 10(9)/l. Seven patients had a good response with a platelet count that increased to between 50 and 150 x 10(9)/l (median 121 x 10(9)/l). Two patients were resistant both to DEX and IV IgG. The operation was uneventful in all the patients, including the 2 who had resistant ITP and were operated on while their platelet count was very low (5 x 10(9)/l). Thus, high-dose DEX, which is an easy, effective and inexpensive treatment, is recommended for the preparation of ITP patients prior to splenectomy.     

Treatment of hepatitis C related thrombocytopenia with interferon alpha.

Thrombocytopenia is a common extrahepatic manifestation of hepatitis C (HCV) infection. Treatment with steroids may be effective, but can exacerbate the viral infection. Interferon alpha (INF) has documented efficacy in the treatment of HCV, but its use in the treatment of HCV thrombocytopenia is controversial. We treated eight patients with HCV-related thrombocytopenia, who had platelet counts of fewer than 50 x 10(9)/l (range: 16 to 46 x 10(9)/L) with INF 3 MU SQ three times a week. Planned duration of treatment was 24 weeks. Five patients had no evidence of hepatic cirrhosis, three had cirrhosis, and two had palpable splenomegaly. Only three patients tolerated the full course of treatment, and all three had improvement in their platelet counts to greater than 50 x 10(9)/l. Two other patients had improvement in platelet counts to more than 50 x 10(9)/l with shorter duration of treatment (six and 16 weeks, respectively). The mean increase in platelet count in the five responders was 44 x 10(9)/lL (range: 28 to 90 x 10(9)/l). The average peak platelet count in the responders was 81 x 10(9)/l (range: 62 to 136 x 10(9)/l). Duration of response ranged from four to 18+ months, with the shortest responses observed in the two patients treated with a shorter course of INF. Response was independent of the presence of cirrhosis. Responding patients had improvement in hepatic transaminases, reduction in cryoglobulin and anticardiolipin antibodies, and HCV plasma RNA when tested. Relapse was associated with an increase in these laboratory markers of HCV infection. We conclude that INF can be an effective treatment in patients with HCV-related thrombocytopenia.     

Variable levels of carry over on platelet counts < or = 20 x 10(9)/l with the Bayer Advia 120

Accurate platelet counts are essential for the safe management of severe thrombocytopenia (platelet counts < or = 20 x 10(9)/l). The effect of carry over on platelet counting in severe thrombocytopenia was investigated by performing counts before and after saline rinses on three Bayer Advia 120 automated blood counters. Counts were performed in both primary and manual closed tube system modes on two instruments and in manual open tube mode on a third. A total of 194 samples with platelet counts < or = 20 x 10(9)/l were studied. First counts were significantly higher in all groups. The magnitude of the difference varied both by analyser and counting mode. Carry over was minimal with one analyser in primary mode and second counts were on average only 5.5% lower; on a second analyser in manual closed tube system mode second counts were on average 37.7% lower. A first count of > or = 10 x 10(9)/l fell to <10 x 10(9)/l on the second count in 35 of 145 samples (24.1%). In five such samples, all tested on one analyser, the second count was <50% of the value of the first count. Two of 49 (4.1%) first counts of <10 x 10(9)/l increased to > or = 10 x 10(9)/l on repeat. These results show a variable and often potentially clinically important carry-over effect on severely thrombocytopenic samples using the Advia 120.     

Successful intravenous immune globulin therapy for human immunodeficiency virus-associated thrombocytopenia

High-dose intravenous (IV) immune globulin was used to treat human immunodeficiency virus (HIV)-associated thrombocytopenia four times in three patients. The average platelet count at initiation of therapy was 12 x 10(9)/L (12 x 10(3)/mm3), and the platelet count after therapy was 159 x 10(9)/L (159 x 10(3)/mm3), giving a mean increase of 147 x 10(9)/L (147 x 10(3)/mm3) (1225%). The conditions of two of these patients were refractory to corticosteroids, but giving IV immune globulin along with steroids appeared to enhance the response to IV immune globulin. A review of the literature revealed that 53 (88%) of 60 patients with HIV-associated thrombocytopenia responded to IV immune globulin with platelet counts greater than 50 x 10(9)/L (50 x 10(3)/mm3). We conclude that IV immune globulin therapy achieves transient elevations in platelet counts to levels that control bleeding and permit surgery in patients with severe, HIV-associated thrombocytopenia.     

Relationships between platelet counts, platelet volumes and reticulated platelets in patients with ITP: evidence for significant platelet count inaccuracies with conventional instrument methods

The platelet count has a primary role in the diagnosis and treatment of idiopathic thrombocytopenic purpura (ITP). This study analysed the accuracy of ITP patient platelet counts determined by Abbott CD-Sapphire (impedance/optical) and Bayer Advia 120 (optical) analyses, compared with a reference immunoplatelet method. Instrument platelet estimates showed broad equivalence in the higher range of observed values, but significant discrepancies against the immunoplatelet count were seen when platelet counts were <10 x 10(9)/l. CD-Sapphire mean platelet volume (MPV) results revealed increased (>12 fl) platelet volumes in eight of eight ITP patients with counts of <20 x 10(9)/l compared with 6/6 and 5/13 patients with platelet counts of 20-50 and >50 x 10(9)/l. In contrast, Bayer Advia MPV values showed no relationship with the platelet count. Increased reticulated platelets were associated with an increasing CD-Sapphire MPV (R(2) = 0.61) and a decreasing platelet count. High (>40%) reticulated platelet values were seen in 9/9 patients with immunoplatelet counts of <20 x 10(9)/l compared with 0/19 patients with platelet counts above 20 x 10(9)/l. There may be a need for caution in the interpretation of platelet counts in ITP patients obtained with conventional instrument methods, and therapeutic decisions should ideally be validated by reference immunoplatelet procedures.     

Superior effect of intravenous anti-D compared with IV gammaglobulin in the treatment of HIV-thrombocytopenia: results of a small, randomized prospective comparison

This small, prospective, randomized study compared increases in platelet counts and duration of response after intravenous gammaglobulin (IVIG) and IV anti-D in patients with HIV-related thrombocytopenia (HIV-TP). Nine Rh+, nonsplenectomized HIV-positive patients with thrombocytopenia were treated sequentially, in random order, with IVIG and IV anti-D in a cross over design, receiving each therapy for 3 months. Peak platelet counts and duration of effect after each treatment were compared. In addition, viral load measurements and CD4 counts were followed serially, as well as thrombopoietin levels. IV anti-D resulted in a mean peak platelet count of 77 x 10(9)/L compared to only 29 x 10(9)/L after IVIG (P = 0.07). The mean duration of response was significantly longer in patients treated with anti-D (41 days) compared to IVIG (19 days, P = 0.01). No consistent changes were seen in the CD4 counts or viral load measurements as a result of either therapy. Thrombopoietin levels were normal in all patients despite often severe thrombocytopenia. Anti-D was more efficacious than IVIG for the treatment of HIV-TP, confirming and extending previous results. Anti-D should be the first line therapy in HIV-positive, Rh+ patients, when antiretroviral agents are not indicated, not effective, or there is an urgent need to increase the platelet count.     

High-dose intravenous gammaglobulin (IVG) in neonatal immune thrombocytopenia

Recent reports suggest that intravenous gammaglobulin (IVG) may be an effective treatment modality in patients with immune thrombocytopenia (ITP). Two newborns with isoimmune thrombocytopenia secondary to HLA-A2 and PLA1 platelet antigen incompatibilities with their respective mothers and two newborns with thrombocytopenia secondary to maternal ITP were treated with IVG 400 mg/kg/day x 5 days. One patient was exposed to steroids in utero; only one mother was thrombocytopenic at the time of delivery. All patients were severely thrombocytopenic on day 1 of treatment with mean platelet count of 5.7 x 10(9)/L. All had petechiae and positive quaiac stools, and patients with isoimmune thrombocytopenia had CT scan evidence of intracranial bleeds. The mean platelet count after 24 hr was 26.7 x 10(9)/L and the average platelet increase was 21 x 10(9)/L and 33 x 10(9)/L at 24 and 48 hr, respectively. The two cases with isoimmune thrombocytopenia had sustained platelet increases; the two cases secondary to maternal ITP had transient platelet elevations. IVG can rapidly elevate the platelet count in these patients, especially those with severe bleeding manifestations.     

HIV-seropositive thrombocytopenia: the action of zidovudine.

The action of zidovudine when administered to individuals with severe HIV thrombocytopenia was investigated. Four individuals with platelets less than 50 x 10(9)/l and CD4 cells greater than 200 x 10(6)/l were treated with 600 mg zidovudine per day for 6 weeks, no drug for 6 weeks, 1200 mg zidovudine per day for 6 weeks, then no drug for 6 weeks. Glycocalicin, a platelet protein which correlates inversely with platelet survival, was assayed before and after treatment. Glycocalicin indices were also measured in four additional individuals with HIV thrombocytopenia. Platelet counts rose 2.5-fold [95% confidence interval (Cl), 2.0-3.0)] for four subjects who received 600 mg zidovudine per day and 4.9-fold (95% Cl, 4.0-5.8) for three subjects receiving 1200 mg zidovudine per day. Platelet counts declined during drug-free intervals. Plasma glycocalicin indices were elevated in all with untreated HIV thrombocytopenia. Indices fell after zidovudine treatment in six of seven individuals, suggesting that zidovudine prolonged platelet survival. Analysis of 170 HIV-seropositive asymptomatic individuals [mean CD4 count 474 x x 10(6)/l, standard deviation (s.d.) 245 x 10(6)/l] revealed that 14 (8%) had less than 125 x 10(9)/l platelets but only 2 (1%) had less than 50 x 10(9)/l platelets. Platelet counts increased spontaneously in eight individuals with mild HIV thrombocytopenia among the 10 for whom repeat counts were available.     

Efficacy and safety of splenectomy in adult chronic immune thrombocytopenia

For patients with adult chronic immune thrombocytopenia (ITP) splenectomy (SE) is a highly effective treatment, but there are still uncertainties regarding the long-term efficacy and safety. We evaluated the long-term efficacy and safety of SE in 48 consecutive adult patients with chronic ITP (26 women, 22 men) who underwent SE between 1990 and 2001 at the General Hospital in Vienna, Austria. All patients had no remission after steroid treatment and were steroid dependent. The median age at the time of SE was 44 years (range: 16-77 years). Of 48 patients, 37 achieved a complete remission (CR, platelet count >100 x 10(9)/l), 8 a partial remission (PR) (platelet count 30-100 x 10(9)/l), and 2 had no response (NR). The probability of the overall survival was 98% at a median postsplenectomy observation time of 3.5 years. Seven patients with CR and four patients with PR relapsed. There were no relapses after 1 year. The probability of continuous complete remission (CCR) at 10 years was 79%. The probability of having a platelet count of >100 x 10(9)/l or >30 x 10(9)/l was 61% and 67%, respectively, at 5 and 10 years after splenectomy. Of the 11 relapsed patients, 5 had a second CR ( n=3) or PR ( n=2). The postoperative platelet count was the best predictor for a long-term remission. All patients with postoperative platelet counts >250 x 10(9)/l remained in CR. Patients aged >45 years had a similar success rate as compared with younger patients. Three patients had infections (one pneumonia and two fever of unknown origin) requiring hospitalization, but none had overwhelming septicemia.     

Low incidence of thrombocytopenia with porcine mucosal heparin. A prospective multicenter study

We treated 193 patients either intravenously (94) or subcutaneously (99) for at least 5 days with porcine intestinal mucosal heparin and followed them up prospectively with frequent platelet counts to determine the incidence of heparin-related thrombocytopenia and arterial thrombosis. None of the patients in the study developed severe thrombocytopenia (platelet count, less than 100 x 10(9)/L) or arterial thrombosis. Eight patients had a platelet count of 100 to 140 X 10(9)/L on one occasion, with a count of greater than 140 x 10(9)/L on the subsequent measurement. The mean (+/- SD) values of the initial and lowest platelet counts during therapy in all patients were 288 +/- 100 x 10(9)/L and 253 +/- 88 x 10(9)/L, respectively, with the lowest counts occurring on day 4.1 +/- 4.2. A least-squares line was computed for each patient to fit the day and counts; the slopes were significantly different from zero and negative in 7.8% of patients and positive in 14.5%. This multicenter study confirms the reports that the incidence of heparin-related severe thrombocytopenia and arterial thrombosis is distinctly low in patients treated with porcine-mucosal heparin.     

An open-label, unit dose-finding study of AMG 531, a novel thrombopoiesis-stimulating peptibody, in patients with immune thrombocytopenic purpura

Abstract The objective of this open label, phase 1-2, multicentre trial was to evaluate the safety of AMG 531, a novel thrombopoiesis-stimulating peptibody, and its effect on platelet counts in adults with immune thrombocytopenic purpura. Four patients were assigned to each of four unit-dose cohorts: 30, 100, 300 or 500 microg, administered subcutaneously on days 1 and 15 (or day 22 if the day 15 platelet count was >50 x 10(9)/l). Safety was assessed by adverse event (AE) monitoring, clinical laboratory studies and antibody assays. Platelet response was defined as a platelet count double the baseline value and between 50 and 450 x 10(9)/l. Sixteen patients (10 women) were enrolled. The 500-microg cohort was discontinued because the first patient's platelet count became unacceptably high. AEs were generally expected and mild or moderate; the most frequent was headache (eight of 16 patients). Two patients experienced serious AEs related to AMG 531 (severe headache and elevated serum lactic dehydrogenase; thrombocytopenia). Platelet responses occurred with all doses and with a dose equivalent to >/=1 microg/kg in eight of 11 patients. In summary, patients tolerated AMG 531 well at the doses tested. No anti-AMG or antithrombopoietin antibodies were detected. Doses equivalent to >/=1 microg/kg increased platelet counts.     

Danazol for the treatment of thrombocytopenia in patients with myelodysplastic syndrome

Thrombocytopenia is a poor prognostic indicator in the myelodysplastic syndromes (MDS). Treatment options for patients with symptomatic thrombocytopenia are limited. Danazol, an attenuated androgen, may have some efficacy in increasing the platelet count of patients with MDS. We retrospectively reviewed 33 patients with primary MDS who were treated with danazol for 6 or more weeks. After 6 weeks on danazol, the mean platelet count increased from 42 x 10(9)/L to 60 x 10(9)/L (P < 0.015), and 25 out of 33 patients (76%) had an increase in their platelet counts. Following 12 weeks of treatment, the mean platelet count increased to 67 x 10(9)/L (P < 0.005), and 21 out of 29 patients (72%) had an increase in their platelet counts. Seven out of nine patients no longer required platelet transfusions because bleeding stopped after 6 weeks on danazol. Mean duration of response was 10 months (range 2-68 months). Responses were seen in all French-American-British (FAB) subtypes and in all International Prognostic Scoring System (IPSS) scores. Therapy was well tolerated. Danazol may be effective in MDS patients who are thrombocytopenic.     

Rituximab therapy for chonic and refractory immune thrombocytopenic purpura: a long-term follow-up analysis

The aim of this study was to evaluate the long-term response to rituximab in patients with chronic and refractory immune thrombocytopenic purpura (ITP). Adults with ITP fail to respond to conventional therapies in almost 30% of cases, developing a refractory disease. Rituximab has been successfully used in these patients. We used rituximab at 375 mg/m2, IV, weekly for a total of four doses in 18 adult patients. Complete remission (CR) was considered if the platelet count was >100 x 10(9)/l, partial remission (PR) if platelets were >50 x 10(9)/l, minimal response (MR) if the platelet count was >30 x 10(9)/l and <50 x 10(9)/l, and no response if platelet count remained unchanged. Response was classified as sustained (SR) when it was stable for a minimum of 6 months. Median age was 43.5 years (range, 17 to 70). Median platelet count at baseline was 12.5 x 10(9)/l (range, 3.0 to 26.3). CR was achieved in five patients (28%), PR in five (28%), MR in four (22%), and two patients were classified as therapeutic failures (11%). Two additional patients were lost to follow-up. The median time between rituximab therapy and response was 14 weeks (range, 4 to 32). SR was achieved in 12 patients (67%). There were no severe adverse events during rituximab therapy. During follow-up (median, 26 months; range, 12 to 59), no other immunosuppressive drugs were used. In conclusion, rituximab therapy is effective and safe in adult patients with chronic and refractory ITP. Overall response rate achieved is high, long term, and with no risk of adverse events.     

The long-term efficacy of Helicobacter pylori eradication therapy in patients with idiopathic thrombocytopenic purpura

BACKGROUND AND AIM: A beneficial effect of Helicobacter pylori (H. pylori) eradication in patients with H. pylori-positive idiopathic thrombocytopenic purpura (ITP) has been reported by several investigators; however, it was not clear whether the recovered platelet count after H. pylori eradication was maintained for a long period. METHOD: Thirty-eight ITP patients who were examined for H. pylori infection were assessed. H. pylori-positive patients received a standard antibiotic therapy for H. pylori eradication. We investigated the long-term effect of H. pylori eradication on platelet recovery in patients with H. pylori-positive ITP. RESULTS: Of the 38 ITP patients, 26 (68.4%) were positive for H. pylori. The response rate of platelet recovery was 56.5% (13/23 patients). Twelve patients showed complete response (CR) and one showed partial response (PR). The mean platelet counts 6 months after eradication significantly increased from 31 x 10(9)/L to 129 x 10(9)/L in 23 H. pylori-eradicated patients (P < 0.001). The median platelet counts of responders 1, 2, 3, and 4 years after eradication were 168 x 10(9)/L (n = 10), 193 x 10(9)/L (n = 9), 168 x 10(9)/L (n = 7), and 243 x 10(9)/L (n = 4) after a mean follow-up of 25.8 months. CONCLUSION: Eradication therapy for H. pylori-positive patients with ITP was effective and a favorable effect was maintained for long periods.     

Thrombocytopenia in patients with malaria: automated analysis of optical platelet counts and platelet clumps with the Cell Dyn CD4000 analyser

Platelet counts and automated detection of platelet clumps were evaluated by optical analysis with the Abbott CD4000 analyser (Abbott Diagnostics, Santa Clara, CA, USA) in this South African study of 828 samples referred for malaria investigations. Based on microscopy (Micro) and rapid tests (RT) for HRP2 protein and parasite-associated LDH, malaria negative samples (n = 417) were defined as Micro-, RT-. Convalescent cases (n = 64) were Micro-, RT+ and had a recent record of positive microscopy. Malaria positive cases were subdivided into Micro+ (n = 315) and Micro-, RT+, PCR+ (polymerase chain reaction) (n = 32) subgroups. The mean platelet count for Micro+ cases (89.7 x 10(9)/l) was significantly lower than both the malaria negative (mean 212.6 x 10(9)/l) and convalescent malaria (mean 152.8 x 10(9)/l) groups; 89% of microscopy positive cases were thrombocytopenic (< 150 x 10(9)/l) and 30% had severe thrombocytopenia (< 50 x 10(9)/l). For comparison, 32% of the 417 malaria negative samples were thrombocytopenic and 6% of these were severe. Two thirds of samples with parasitaemia above 10% had platelet counts of < 50 x 10(9)/l while the counts were largely independent of parasite numbers when the parasitaemia was below 10%. Thirty percent of samples with microscopically detectable parasites had a PltClmp flag compared to 13% of the malaria negative group but, when the actual platelet count was taken into account, it became apparent that appearance of the flag was primarily associated with thrombocytopenia per se rather than malaria status. In most samples with a PltClmp flag, the CD4000 optical platelet clump 'signature' was indicative of small platelet aggregates and giant platelets. Morphological examination confirmed the presence of varying numbers of small platelet aggregates (3-12 individual platelets), often together with increased giant platelets, in many samples with a PltClmp flag. The observations suggest that while patients with malaria may be predisposed to the development of thrombocytopenia, a reduced platelet count in some patients may also be due in part to pseudo-thrombocytopenia.     

Improvement of platelet counts in steroid-unresponsive idiopathic immune thrombocytopenic purpura after short-course therapy with recombinant alpha 2b interferon [see comments]

In 13 patients with severe steroid-refractory idiopathic immune thrombocytopenia (ITP), a short course of recombinant alpha 2b interferon (IFN), given at a dose of 3 MU for 12 doses, caused a significant increase in platelet count in 11 patients. The rise in platelet count occurred following completion of the short course of IFN in 10 patients and occurred during therapy in one patient. Three patients showed an increase to normal platelet counts within 14 days of discontinuing the drug, eight showed a partial response, with a platelet count increase from 30 to 100 x 10(9)/L, and two patients showed minimal response. One complete responder relapsed at 5 months from initial response, and a further course of alpha 2b IFN caused a second prompt response with a rise of platelet count to supranormal levels. Short-course alpha 2b IFN can be recommended as a therapy for severe ITP. Responses are seen in splenectomized and nonsplenectomized subjects, and thrombocytopenia is not exacerbated during treatment.     

Analysis of outcome of laparoscopic splenectomy for idiopathic thrombocytopenic purpura by platelet count

Laparoscopic splenectomy (LS) is now performed routinely in patients with idiopathic thrombocytopenic purpura (ITP) refractory to the medical treatment. Low preoperative platelet count was deemed to be a contraindication for a laparoscopic approach; however, there is no data reporting the outcome in those patients. We aimed to evaluate the influence of the preoperative platelet count on the operative and postoperative course and complication rate. Retrospective cohort study that was conducted in tertiary care university-affiliated medical center and included 110 consecutive patients who underwent LS. All patients were divided into three groups by their preoperative platelet counts: 50 x 10(9)/L (n = 80). The outcome and the influence of preoperative factors predictive of complications, blood transfusion, and length of stay were compared between the groups. Patients with a platelet count of 20 x 10(9)/L before surgery. Patients with counts >20 x 10(9)/L can safely undergo LS.     

Thrombocytopenia in malaria.

The relationship between platelet counts and platelet bound (direct) or platelet directed (indirect) serum antibody concentrations was studied in 17 patients with Plasmodium falciparum malaria and 12 patients with P. vivax malaria. Platelet counts rose with recovery from infection from 196 +/- 84 x 10(9)/l (mean +/- SD) and 195 +/- 34 x 10(9)/l to 319 +/- 99 and 283 +/- 62 x 10(9)/l respectively (p less than 0.002), but there was no relationship between either absolute platelet count or changes in counts and either indirect or direct platelet antibody levels. These findings suggest that a non-immunologically mediated mechanism is involved in the pathogenesis of thrombocytopenia in malaria.     

HIV-related severe thrombocytopenia in intravenous drug users: prevalence, response to therapy in a medium-term follow-up, and pathogenetic evaluation

Severe thrombocytopenia (TP) accounted for 5.3% of cases in a consecutive series of 380 HIV-infected intravenous drug users (IVDUs) at presentation. Forty-one of 53 subjects with severe TP showed haemorrhages and were treated as follows: ten were splenectomized, 17 were given high-dose intravenous immunoglobulins (HDIg), and 10 received anti-Rh(D) immunoglobulins (anti-Rh Ig). Splenectomy induced a complete clinical response in all cases: four out of 10 patients maintained platelet counts greater than 100 x 10(9)/l. HDlg gave a good clinical response in all patients, but eight out of 17 suffered haemorrhages during the follow-up and recall treatments were necessary. Six out of 10 patients treated with anti-Rh lg maintained platelet counts greater than 30 x 10(9)/l, but in two cases the treatment was interrupted because of severe haemolysis. No patient progressed to overt AIDS during the follow-up. Splenectomized patients in particular did not show adjunctive risks of worsening of the HIV-related clinical picture. A platelet kinetic study performed in 20 patients with severe HIV-related TP suggests a possible role for platelet sequestration in TP of HIV-infected IVDUs, in which a liver involvement is very frequent.     

Bone marrow toxicity caused by azathioprine in inflammatory bowel disease: 27 years of experience.

Myelosuppression is an important and potentially lethal complication of azathioprine treatment. The blood count has been reviewed in all patients treated with azathioprine for inflammatory bowel disease over 27 years in one hospital. Altogether 739 patients (422 with Crohn's disease, 284 with ulcerative colitis, and 33 with indeterminate colitis) were treated with 2 mg/kg/day azathioprine for a median of 12.5 months (range 0.5-132) between 1964 and 1991. Full blood counts were performed monthly for the duration of treatment. In 37 patients (5%) who developed bone marrow toxicity, the drug was withdrawn or the dose reduced. Thirty two of these patients were asymptomatic and five developed symptoms. Leucopenia (white blood count less than 3.0 x 10g/l) occurred in 28 (3.8%) patients, in nine of whom it was severe (white blood count < 2.0 x 10(9)/l). Of these nine patients, three were pancytopenic: two died from sepsis and the other had pneumonia but recovered. A further two patients with severe leucopenia developed a mild upper respiratory infection only. Thrombocytopenia (platelet count < 100,000 x 10(6)/l) in 15 patients was associated with leucopenia in six and developed in isolation in a further nine (total 2%). Isolated thrombocytopenia was never clinically severe. Myelotoxicity from azathioprine developed at any time during drug treatment (range 2 weeks-11 years after starting the drug) and occurred either suddenly or over several months. Bone marrow suppression as a result of azathioprine treatment is uncommon when a moderate dose is used, but is potentially severe. Leucopenia is the commonest and most important haematological complication. Regular monitoring of the full blood count is recommended during treatment.