Dapsone-induced methemoglobinemia: "Saturation gap"-The key to diagnosis

A Case study of polypharmacy-induced serotonin syndrome in a cancer patient

ABSTRACT

Polypharmacy in cancer care can be complex and detrimental, particularly among younger patients, who can be easily overlooked. This report showcases a 54-year-old woman with cancer, treated for dapsone-induced methemoglobinemia with methylene blue (MB), subsequently developing serotonin syndrome (SS) due to concurrent serotonin-active medications. This case highlights the critical impact of polypharmacy, emphasizing the necessity for acute care providers to diligently assess medication interactions, especially in emergencies. It underscores the importance of considering alternative treatments and the vigilant monitoring of symptoms indicative of adverse drug interactions to ensure patient safety and optimize outcomes in complex therapeutic scenarios.

Dapsone-induced methemoglobinemia and hemolysis in a woman without G6PD deficiency presenting with idiopathic urticaria

BACKGROUND

The appearance of bite cells associated with methemoglobinemia can be caused by oxidizing drugs such as dapsone in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency or high drug serum levels. Bite cells are often pathognomonic for oxidant injury in patients with G6PD deficiency and suggest active hemolysis.

CASE PRESENTATION

We report a case of a woman with no prior history of G6PD deficiency who presented with anemia, methemoglobinemia and bite cells on peripheral blood smear after dapsone therapy for new onset idiopathic urticaria. Laboratory tests for G6PD, blood count and liver function were within normal limits prior to initiation of therapy. During the patient's hospital course, moderate methemoglobinemia and anemia were identified despite mildly increased serum G6PD level. These pathologies were reversed upon stopping dapsone therapy.

CONCLUSION

This case highlights the potential for therapeutic levels of dapsone to induce side effects in patients without G6PD deficiency and highlights the importance of routine blood monitoring for anemia and hemolysis during the course of drug therapy.

SARS-CoV-2 infection, pulse oximetry, and interpretive caveats

Hypoxaemia in COVID-19 does not necessarily imply COVID pneumonia or post-COVID lung fibrosis, and the caveats of finger pulse oximetry should be remembered. Drug-induced methaemoglobinemia should be considered in individuals with unexplained cyanosis, refractory hypoxaemia, or the presence of a saturation gap. Here, we share our recent encounter of ‘spurious hypoxia’ in a patient with COVID-19 and methaemoglobinemia.

Methaemoglobinaemia in the perioperative period with regional block

Methaemoglobin is a form of haemoglobin with oxidised ferric (+3) iron rather than ferrous (+2) iron, which causes a leftward shift in the oxyhaemoglobin dissociation curve and prevents oxygen delivery. Anaesthesiologists need to be familiar with this differential diagnosis for hypoxia given the use of drugs in the perioperative setting known to induce methaemoglobinaemia, including benzocaine and lidocaine, antibiotics such as dapsone and anaesthetic gases, including nitric oxide. This case report details an interesting case of symptomatic methaemoglobinaemia in the perioperative period in the setting of dapsone use and an erector spinae block performed with ropivacaine.

Methemoglobinemia Unmasked by Use of Sodium Nitroprusside and Hypothermia in a Case of Chronic Thromboembolic Pulmonary Hypertension During Pulmonary Endarterectomy: A Case Report

In performing pulmonary endarterectomy (PEA) for a patient with chronic thromboembolic pulmonary hypertension (CTEPH), we encountered methemoglobinemia that was unmasked by hypothermia while on cardiopulmonary bypass (CPB). The patient on dapsone therapy for antiphospholipid antibody syndrome had developed acquired methemoglobinemia that went undiagnosed because her cyanosis was believed to be due to CTEPH and the resulting ventilation-perfusion (V/Q) mismatch. Although pharmacological triggers for methemoglobin are well known, causation by hypothermia is not described. Monitoring saturation while on CPB was challenging because of nonpulsatile blood flow but was overcome using cerebral oximetry.

Unusual cause of persistent dyspnea in a patient with nephrotic syndrome: dapsone-induced methemoglobinemia

Acquired methemoglobinemia is a rare, but important cause of tissue hypoxemia, which often results from commonly prescribed medications. We report a case of an 83-year-old female with stage III chronic kidney disease, who was started on high-dose prednisone for nephrotic syndrome and dapsone for pneumocystis jirovecii pneumonia prophylaxis. A week after initiation of dapsone, this patient presented with shortness of breath, and an oxygen saturation gap while on supplemental O2 via nasal cannula, with no obvious cardiopulmonary cause. Methemoglobin level was elevated on arterial blood gas. Our patient was treated with IV methylene blue. Dapsone was determined to be the culprit and immediately discontinued. Patient responded with a rapid decrease in methemoglobin levels and resolution of symptoms. This case report highlights the importance of maintaining a high index of suspicion and careful review of medication history for prompt and successful management of methemoglobin poisoning, as not all patients present with classical signs of methemoglobinemia such as cyanosis and/ or dark red blood.

A case of dapsone-induced methaemoglobinaemia

Methaemoglobinaemia is an uncommon but potentially serious condition. It can be caused by congenital or acquired cause. Drug-induced methaemoglobinaemia is the commonest cause of acquired methaemoglobinaemia. The clinical signs and symptoms of methaemoglobinaemia include dyspnoea, desaturation, presence of saturation gap, headache, nausea and seizures depending on level of serum methaemoglobinaemia. We illustrate a case of dapsone-induced methaemoglobinaemia and its successful treatment by intravenous methylene blue.

A case of DAPSONE INDUCED METHEMOGLOBINEMIA

Methemoglobinemia (MetHb) being a rare cause of cyanosis is generally not considered in its differential diagnosis. Methemoglobinemia is an abnormal Hb produced physiologically by auto-oxidation. If this process of auto oxidation is impaired either due to genetic defect or due to exogenous drugs/ toxins, its level starts rising. Once it is > 3%, tissue hypoxia ensues. Here is a case of dapsone induced MetHb and is reported in a young girl with central cyanosis, and was treated successfully with methylene blue. Methemoglobinemia should be considered in differential diagnoses of cyanosed patient with normal ABGs, PaO₂ and cardio-respiratory status. If left untreated, the disease can be fatal.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Drug-Induced Hematological Cytopenia in Kidney Transplantation and the Challenges It Poses for Kidney Transplant Physicians

Drug-induced hematological cytopenia is common in kidney transplantation. Various cytopenia including leucopenia (neutropenia), thrombocytopenia, and anemia can occur in kidney transplant recipients. Persistent severe leucopenia or neutropenia can lead to opportunistic infections of various etiologies. On the contrary, reducing or stopping immunosuppressive medications in these events can provoke a rejection. Transplant clinicians are often faced with the delicate dilemma of balancing cytopenia and rejection from adjustments of immunosuppressive regimen. Differentials of drug-induced cytopenia are wide. Identification of culprit medication and subsequent modification is also challenging. In this review, we will discuss individual drug implicated in causing cytopenia and correlate it with corresponding literature evidence.

Acute visual loss following dapsone-induced methemoglobinemia and hemolysis

OBJECTIVE

While methemoglobinemia is a possible complication of chronic dapsone therapy or of acute overdose, serious adverse manifestations related to methemoglobin formation remain rare. We present an unusual case with severe ischemic retinal injury.

CASE REPORT

A 30-year-old African woman presented with a sudden decrease of visual acuity secondary to retinal ischemia. She was chronically treated with dapsone (50 mg/day) for a dermatologic disease and denied any drug overdose. However, the determination of serum dapsone level on admission revealed a largely supratherapeutic concentration (20,044 μg/ml compared with 1-3.5 ± 0.5 μg/ml for therapeutic levels). The methemoglobin level at admission was 32% (sulfhemoglobin 1.2%), with hemoglobin level, 7.4 g/dl, schistocytes count, 2-5%, lactate dehydrogenase level, 580 IU/l, and haptoglobin level, < 10 mg/dl. The patient had both alpha-thalassemia and sickle cell trait. She was treated with methylene blue, vitamin C, and exchange transfusion. There was no improvement in visual symptoms over time.

CONCLUSIONS

In a patient with supratherapeutic serum levels of dapsone, the severity of visual injury was associated with dapsone-induced methemoglobinemia and hemolysis, and perhaps also with some hematologic predisposing factors.