Treatment options in sulfamethoxazole-trimethoprim-induced thrombocytopenic purpura

Life-Threatening Thrombocytopenia Secondary to Trimethoprim/Sulfamethoxazole

Thrombocytopenia is an uncommon side effect of trimethoprim/sulfamethoxazole (TMP/SMX) when given in the usual recommended adult dosage. We report a case of severe and possibly life-threatening thrombocytopenia associated with TMP/SMX therapy.

A 92-year-old female presented after a mechanical fall and subsequent intractable bleeding from a laceration on her left leg. She had a history of cellulitis of the lower extremities treated with a 10-day course of TMP/SMX. Her last dose was two days before the visit. The physical examination was significant for a small laceration on her left shin, with persistent oozing of blood. Her blood work was notable for white blood cells (WBC) 9.4×10^9/L (9.4×10^3/mm^3), hemoglobin 125g/L (12.5 g/dL) and platelets 5×10^9/L (5×10^3/mm^3). A repeat platelet count was 4×10^9/L. Prothrombin time was 11 seconds and the international normalized ratio (INR) was one. The TMP/SMX was discontinued and one unit of platelets was transfused. Her platelet count subsequently increased to 108×10^9/L.

Severe thrombocytopenia with a platelet count of ≤10×10^9/Lmay rarely result in the catastrophic spontaneous bleeding. Thus, low platelet counts associated with TMP/SMX carry potential life-threatening complications. The clinicians should be aware of this adverse effect of TMP/SMX, which appears to be dose/duration independent. We suggest careful monitoring of complete blood cell count, especially platelet count, before and during TMP/SMX therapy.

The first reported case of concurrent trimethoprim-sulfamethoxazole-induced immune hemolytic anemia and thrombocytopenia

BACKGROUND

Drug-induced immune hemolytic anemia (DIIHA) and drug-induced immune thrombocytopenia (DIIT) are rare but dangerous complications of pharmacotherapy that may be underrecognized in hematopoietic stem cell transplant (HSCT) patients due to overlap of signs and symptoms with those of more common disease processes.

CASE REPORT

A 61-year-old woman with NK-cell deficiency and GATA-2-associated myelodysplastic syndrome, status post-recent allogeneic HSCT (Day +58), presented with 3 days of acute-onset severe back pain, muscle cramps, and increasingly dark urine. She was found to be anemic, thrombocytopenic, and in acute renal failure. On admission, the direct antiglobulin test was positive for complement (C3) only. After careful review of her medication list, the possibility of DIIHA was raised. She had started taking trimethoprim-sulfamethoxazole (TMP-SMX) for Pneumocystis jiroveci pneumonia prophylaxis 24 days prior on a weekend dose schedule. Serologic tests on peripheral blood samples were performed using standard methods. Drug studies were performed at an immunohematology reference laboratory.

RESULTS

The patient's serum showed hemolysis of donor red blood cells in the presence of TMP-SMX and also TMP-SMX-induced platelet antibodies. The patient was treated with transfusions, hemodialysis, and immunosuppressive agents. Her clinical condition improved and she was discharged after 8 days in stable condition.

CONCLUSION

This case describes the first reported concurrent DIIHA and DIIT due to TMP-SMX-induced antibodies in an HSCT patient. DIIHA and DIIT can present a diagnostic challenge in the setting of intermittent medication dosing.

An uncommon cause of gastrointestinal bleeding in an 84-year-old female

The estimated annual incidence for drug-induced thrombocytopenia is 10 per million. Although fatal consequences are uncommon, life-threatening hemorrhage can occur due to spontaneous bleeding. We report a case of 84-year-old Caucasian female who presented to the emergency department with multiple episodes of bloody bowel movements. One week prior to this admission, she was started on trimethoprim-sulfamethoxazole for the treatment of skin abscess. On admission laboratory results showed platelet count of 4 × 10³/mm³ and hemoglobin of 10.2 g/dL. Because of unstable vital signs, the patient was transferred to the intensive care unit where she received multiple units of platelet and blood transfusion. Drug-induced thrombocytopenia due to TMP/SMX was suspected. Intravenous methylprednisolone was started as well as immune globulin with good clinical response.

ADAMTS13 deficiency and thrombotic thrombocytopenic purpura associated with trimethoprim-sulfamethoxazole

Thrombotic thrombocytopenic purpura (TTP) is a hematological disease characterized by microangiopathic hemolytic anemia and thrombocytopenia. Although the link between ADAMTS13 deficiency and idiopathic TTP has been well-established, the role of trimethoprim-sulfamethoxazole (TMP-SMX) in the pathogenesis of TTP is not yet well elucidated. To the best of our knowledge, there have been only two previous reports linking this medication with the development of TTP. We present the case of a healthy woman, age 26 years, who developed TTP during TMP-SMX therapy for urinary tract infection. She was found to have ADAMTS13 deficiency with anti-ADAMTS13 antibodies. Her condition responded to discontinuation of the TMP-SMX, plasmapheresis, and rituximab therapy. We speculate that the acquired ADAMTS13 deficiency might have been triggered by the TMP-SMX therapy.

A case of isoniazid-induced thrombocytopenia: recovery with immunoglobulin therapy

Treatment for a 51-year-old man with pulmonary tuberculosis was initiated with isoniazid, rifampicin, ethambutol, and pyrazinamide, and discontinued after 3 weeks because of skin rash and itchiness. Isoniazid monotherapy was restarted after 2 weeks. Two days later, the platelet count decreased from 150 to 4×10(3)/mm(3). Despite platelet transfusion and oral corticosteroid treatment, the platelet count did not recover. However, after a 2-day administration of intravenous immunoglobulin, the platelet count recovered to 209×10(3)/mm(3). This report describes a case of isoniazid-induced thrombocytopenia that was reversed with intravenous immunoglobulin, thus highlighting the efficacy of this treatment for this rare condition.

Drug-induced immune thrombocytopenia: pathogenesis, diagnosis, and management

Drug-induced immune thrombocytopenia (DITP) can be triggered by a wide range of medications. Although many cases of DITP are mild, some are characterized by life-threatening bleeding symptoms. The pathogenesis of DITP is complex, in that at least six different mechanisms have been proposed by which drug-induced antibodies can promote platelet destruction. It is possible in many cases to identify antibodies that react with platelets in the presence of the sensitizing drug, but the required testing is technically demanding and not widely available. Therefore, a decision on whether to discontinue an implicated medication in a patient suspected of having DITP must be made on clinical grounds. An algorithm is available that can be helpful in assessing the likelihood that a particular drug caused thrombocytopenia, but the most important aspects of patient management are a high index of suspicion and a careful history of drug exposure in an individual who presents with acute, often severe thrombocytopenia of unknown etiology. How drugs induce platelet-reactive antibodies and how, once formed, the antibodies cause platelet destruction following exposure to the drug is poorly understood. Further studies to address these issues and characterize more completely the range of drugs and drug metabolites that can cause DITP are needed.

Association of drug-serum protein adducts and anti-drug antibodies in dogs with sulphonamide hypersensitivity: A naturally occurring model of idiosyncratic drug toxicity

BACKGROUND

Sulphonamide antimicrobials, such as sulphamethoxazole (SMX), provide effective infection prophylaxis in immunocompromised patients, but can lead to drug hypersensitivity (HS) reactions. These reactions also occur in dogs, with a similar time course and clinical presentation as seen in humans.

OBJECTIVES

Drug-serum adducts and anti-drug antibodies have been identified in sulphonamide HS humans. The aim of this study was to determine whether similar markers were present in dogs with sulphonamide HS.

METHODS

Thirty-four privately owned sulphonamide HS dogs, 10 sulphonamide-'tolerant' dogs, 18 sulphonamide-naïve dogs, and four dogs experimentally dosed with SMX and the oxidative metabolite SMX-nitroso, were tested for drug-serum adducts by immunoblotting, and anti-drug antibodies by ELISA.

RESULTS

Sulphonamide-serum adducts were found in 10/20 HS dogs tested (50%), but in no tolerant dogs. Anti-sulphonamide IgG antibodies were detected in 17/34 HS dogs (50%), but in only one tolerant dog; antibody absorbance values were significantly higher in HS dogs. There was a significant association between the presence of sulphonamide-serum adducts and anti-sulphonamide antibodies (P = 0.009). Anti-drug antibodies were also found in dogs experimentally dosed with SMX-nitroso followed by SMX, but not in a dog dosed with drug vehicle, followed by SMX.

CONCLUSION

Similar humoral markers are present in dogs and humans with sulphonamide HS, supporting the use of dogs as a naturally occurring model for this syndrome in humans. These data suggest the potential use of drug-serum adducts and anti-drug antibodies as markers for sulphonamide HS. Preliminary data indicate that anti-sulphonamide antibodies may be triggered by the SMX-nitroso metabolite, not by the parent drug, in dogs.

Severe thrombocytopenia possibly associated with TMP/SMX therapy

OBJECTIVE

To report a case of possible severe, life-threatening thrombocytopenia associated with trimethoprim/sulfamethoxazole (TMP/SMX) therapy.

CASE SUMMARY

A 54-year-old white woman received a 10-day course of TMP/SMX for treatment of chronic sinusitis. One day after finishing the course of TMP/SMX therapy, the presented to the emergency department because of the development of scattered petechiae on both hands and blood blisters in her mouth. On admission, her complete blood cell count results revealed a severely low platelet count of 2 x 10(3)/mm3. Other laboratory test results were normal, except for elevated blood glucose (nonfasting blood glucose). TMP/SMX was believed to be the most likely cause of thrombocytopenia. She was treated successfully with a transfusion of 2 units of platelets and oral prednisone. Her platelet count increased to 110 x 10(3)/mm3 4 days after discontinuation of TMP/SMX. She was discharged on hospital day 5. On follow-up (2 wk after hospital discharge), her platelet count was normal (351 x 10(3)/mm3).

DISCUSSION

TMP/SMX has been implicated as a cause of thrombocytopenia, which is defined as platelet count < 150 x 10(3)/mm3. Although it is uncommon, spontaneous severe bleeding may occur when platelet count decreases to < or = 10 x 10(3)/mm3. Thrombocytopenia associated with TMP/SMX appears to be an immune-mediated process resulting in platelet destruction by drug-dependent platelet antibodies. Treatment of thrombocytopenia associated with TMP/SMX therapy includes discontinuation of the offending drug and the use of corticosteroids. Platelet transfusion and intravenous immunoglobulin may be required in some patients.

CONCLUSIONS

Thrombocytopenia associated with TMP/SMX therapy can be serious or life threatening because it may result in significant bleeding complications. This hematologic adverse effect of TMP/SMX may occur even with the usual recommended dosage and duration of therapy. Careful monitoring of complete blood cell count, including platelet count, before and during TMP/SMX therapy is suggested.