Case Report: Borderline Lepromatous Leprosy Therapy Complicated by Type 1 Leprosy Reaction and Adverse Reactions with Dapsone and Clofazimine.

Leprosy is a global health issue, causing long-term functional morbidity and stigma. Rapid diagnosis and appropriate treatment are important; however, early diagnosis is often challenging, especially in nonendemic areas. Here, we report a case of borderline lepromatous leprosy accompanied by dapsone-induced (neutropenia, anemia, and methemoglobinemia) and clofazimine-induced (skin discoloration and ichthyosis) side effects and type 1 leprosy reactions during administration of the multidrug therapy. The patient completely recovered without developing any deformities or visual impairment. To ensure early diagnosis and a favorable outcome, clinicians should be aware of the diminished sensation of skin lesions as a key physical finding and manage the drug toxicities and leprosy reactions appropriately in patients on multidrug therapy.

Development of a multivariate predictive model for dapsone adverse drug events in people with leprosy under standard WHO multidrug therapy.

BACKGROUND: The occurrence of adverse drug events (ADEs) during dapsone (DDS) treatment in patients with leprosy can constitute a significant barrier to the successful completion of the standardized therapeutic regimen for this disease. Well-known DDS-ADEs are hemolytic anemia, methemoglobinemia, hepatotoxicity, agranulocytosis, and hypersensitivity reactions. Identifying risk factors for ADEs before starting World Health Organization recommended standard multidrug therapy (WHO/MDT) can guide therapeutic planning for the patient. The objective of this study was to develop a predictive model for DDS-ADEs in patients with leprosy receiving standard WHO/MDT. METHODOLOGY: This is a case-control study that involved the review of medical records of adult (≥18 years) patients registered at a Leprosy Reference Center in Rio de Janeiro, Brazil. The cohort included individuals that received standard WHO/MDT between January 2000 to December 2021. A prediction nomogram was developed by means of multivariable logistic regression (LR) using variables. The Hosmer-Lemeshow test was used to determine the model fit. Odds ratios (ORs) and their respective 95% confidence intervals (CIs) were estimated. The predictive ability of the LRM was assessed by the area under the receiver operating characteristic curve (AUC). RESULTS: A total of 329 medical records were assessed, comprising 120 cases and 209 controls. Based on the final LRM analysis, female sex (OR = 3.61; 95% CI: 2.03-6.59), multibacillary classification (OR = 2.5; 95% CI: 1.39-4.66), and higher education level (completed primary education) (OR = 1.97; 95% CI: 1.14-3.47) were considered factors to predict ADEs that caused standard WHO/MDT discontinuation. The prediction model developed had an AUC of 0.7208, that is 72% capable of predicting DDS-ADEs. CONCLUSION: We propose a clinical model that could become a helpful tool for physicians in predicting ADEs in DDS-treated leprosy patients.

Assessment of Clinical, Histopathological, and Bacteriological Findings in Treated Leprosy Patients with Persistent Skin Lesions: A Retrospective Cohort Study.

Since the introduction of multidrug therapy (MDT), various disabilities/morbidities due to leprosy have been prevented. However, there is a subset of patients in whom the skin lesions do not resolve completely or remain unchanged despite a full course of MDT, which is a great source of anxiety to the patient and their family members. Hence, we tried to ascertain the putative causes and risk factors of persistent skin lesions (PSLs) by analyzing the clinical, histopathological, bacteriological, and drug resistance patterns. This is a retrospective, cohort study wherein 35 patients who had PSLs after completion of MDT were included. The majority of the patients were 18 to 30 years of age, with males predominating. Borderline tuberculoid leprosy was the most common clinical spectrum observed (71.4%). The majority had PSLs distributed predominantly over photo-exposed sites (upper limbs > trunk > face). Eight patients (22.8%) had a history of contact with leprosy patients in their family, and six patients (17.1%) had associated comorbidities. Improvement in histopathological parameters such as a decrease in granuloma fraction was observed in 22 patients (62.8%) with PSLs after release from treatment in comparison with baseline. Four patients (11.4%) were noted to have drug resistance (three to rifampicin and one to dapsone). Thus, our study emphasizes that leprosy patients with PSLs after completion of MDT should undergo histopathological evaluation and drug resistance studies.

Overview and Current Advances in Dapsone Hypersensitivity Syndrome.

PURPOSE OF REVIEW: As a sulfone antibacterial agent, dapsone has been widely used to treat leprosy. Moreover, dapsone is also used in many immune diseases such as herpetic dermatitis because of its anti-inflammatory and immunomodulatory effects. However, dapsone can cause several adverse effects, the most serious being dapsone hypersensitivity syndrome. Dapsone hypersensitivity syndrome is characterized by a triad of eruptions, fever, and organ involvement, which limits the application of dapsone to some extent. RECENT FINDINGS: In this article, we review current research about the interaction model between HLA-B*13:01, dapsone, and specific TCR in dapsone-induced drug hypersensitivity. In addition to the proposed mechanisms, we also discussed clinical features, treatment progress, prevalence, and prevention of dapsone hypersensitivity syndrome. These studies reveal the pathogenesis, clinical features, and prevalence from the perspectives of genetic susceptibility and innate and adaptive immunity in dapsone hypersensitivity syndrome, thereby guiding clinicians on how to diagnose, prevent, and treat dapsone hypersensitivity syndrome.

Seventy years of evidence on the efficacy and safety of drugs for treating leprosy: a network meta-analysis.

OBJECTIVE: The World Health Organization (WHO) recommends multidrug therapy (MDT) with rifampicin, dapsone, and clofazimine for treating leprosy, which is based on very low-quality evidence. Here, we performed a network meta-analysis (NMA) to produce quantitative evidence to strengthen current WHO recommendations. METHOD: All studies were obtained from Embase and PubMed from the date of establishment to October 9, 2021. Data were synthesized with frequentist random-effects network meta-analyses. Outcomes were assessed using odds ratios (ORs), 95% confidence intervals (95% CIs), and P score. RESULTS: Sixty controlled clinical trials and 9256 patients were included. MDT was effective (range of OR: 1.06-1255584.25) for treating leprosy and multibacillary leprosy. Six treatments (Range of OR: 1.199-4.50) were more effective than MDT. Clofazimine (P score=0.9141) and dapsone+rifampicin (P score=0.8785) were effective for treating type 2 leprosy reaction. There were no significant differences in the safety of any of the tested drug regimens. CONCLUSIONS: The WHO MDT is effective for treating leprosy and multibacillary leprosy, but it may not be effective enough. Pefloxacin and ofloxacin may be good adjunct drugs for increasing MDT efficacy. Clofazimine and dapsone+rifampicin can be used in the treatment of a type 2 leprosy reaction. Single-drug regimens are not efficient enough to treat leprosy, multibacillary leprosy, or a type 2 leprosy reaction. AVAILABILITY OF DATA AND MATERIALS: All data generated or analyzed during this study are included in this published article [and its supplementary information files].

Implementation of genetic screening test to reduce the incidence of dapsone hypersensitivity syndrome among patients with leprosy in Papua, Indonesia: a study protocol.

INTRODUCTION: The mainstay of leprosy treatment is multidrug treatment (MDT), which contains rifampicin, dapsone and clofazimine. The occurrence of dapsone hypersensitivity syndrome (DHS), a sudden, potentially fatal and traumatic adverse reaction due to dapsone, may affect treatment adherence and may result in fatality if untreated. Before MDT administration, screening for HLA-B*13:01 in patients with leprosy can potentially reduce DHS risk. The study aims to assess the effectiveness of using a screening test for HLA-B*13:01 in reducing the incidence of DHS and to evaluate the feasibility of using the quantitative PCR-based screening tool as DHS predictors before dapsone administration using individual patient testing in a referral centralised-lab model. METHODS AND ANALYSIS: A total of 310 newly diagnosed patients with leprosy will be recruited from health centres in two highly endemic districts in Indonesia. Dried blood will be taken on filter paper as the specimen receptacle to collect DNA from the patients and transported at room temperature to the leprosy referral laboratory before MDT administration. Checking for HLA-B*13:01 from human DNA is performed using the Nala PGx 1301 V.1 kit. The results will be shared with the leprosy health workers on the site via phone call and courier. Patients with a positive test result will be treated with MDT without dapsone, and patients with a negative result will be treated with complete MDT. Physical examination (weight, height, skin, muscle and nerve function examination), complete blood tests (including renal function test) will be carried out at baseline. Follow-up will be performed at the fourth and eighth weeks to observe any development of adverse drug reactions. ETHICS AND DISSEMINATION: The ethical approval for the study was issued by the Ethical Committee of the National Institute of Health Research and Development, Ministry of Health, Indonesia. Written informed consent will be sought from all participants.

Dapsone for the treatment of acne vulgaris: do the risks outweigh the benefits?

Dapsone is a "4,4'-diamino diphenyl sulfone" compound and an aniline derivative from synthetic sulphones. Sulphonamides were first used in humans as antimicrobial agents to treat streptococcal infections. Dapsone derived from sulphonamides was first used in the treatment of leprosy in 1940. Today, Dapsone treatment is among the treatment options for many dermatological diseases. Acne vulgaris is a chronic inflammatory disease, which causes scar formation and changed pigmentation. Acne affects 85% of teenagers, but can occur at any age and can last into adulthood and even lifelong. Through its antimicrobial, anti-inflammatory, and antioxidant effects, dapsone treatment (local or systemic) can also be used in the treatment of acne. Dapsone treatment can cause a variety of side effects that can be categorized as pharmacological, dose-related, allergic, or idiosyncratic reactions. In this review article, the risks and benefits of using dapsone treatment in acne vulgaris will be evaluated in light of the literature.

Challenges in Managing a Lepromatous Leprosy Patient Complicated with Melioidosis Infection, Dapsone-Induced Methemoglobinemia, Hemolytic Anemia, and Lepra Reaction.

BACKGROUND Leprosy is an infection caused by Mycobacterium leprae. An extensive literature search did not reveal many reports of melioidosis in association with leprosy. CASE REPORT A 22-year-old woman, who was diagnosed with multibacillary leprosy, developed dapsone-induced methemoglobinemia and hemolytic anemia, complicated by melioidosis. Methemoglobinemia was treated with methylene blue and vitamin C. Two weeks of ceftazidime was initiated to treat melioidosis, and the patient was discharged on amoxicillin/clavulanic acid and doxycycline as melioidosis eradication therapy. However, she developed drug-induced hypersensitivity. Trimethoprim/sulfamethoxazole, as an alternative treatment for melioidosis eradication, was commenced and was successfully completed for 12 weeks. During the fifth month of multidrug therapy, the patient developed type II lepra reaction with erythema nodosum leprosum reaction, which was treated with prednisolone. Leprosy treatment continued with clofazimine and ofloxacin, and complete resolution of skin lesions occurred after 12 months of therapy. CONCLUSIONS Our case highlighted the challenges posed in managing a patient with multibacillary leprosy with multiple complications. Clinicians should be aware that dapsone-induced methemoglobinemia and hemolysis might complicate the treatment of leprosy. Our case also highlighted the safety and efficacy of combining ofloxacin and clofazimine as a leprosy treatment regimen in addition to gradual steroid dose titration in the presence of type II lepra reaction.

HLA-B*13 :01 Is a Predictive Marker of Dapsone-Induced Severe Cutaneous Adverse Reactions in Thai Patients.

HLA-B*13:01 allele has been identified as the genetic determinant of dapsone hypersensitivity syndrome (DHS) among leprosy and non-leprosy patients in several studies. Dapsone hydroxylamine (DDS-NHOH), an active metabolite of dapsone, has been believed to be responsible for DHS. However, studies have not highlighted the importance of other genetic polymorphisms in dapsone-induced severe cutaneous adverse reactions (SCAR). We investigated the association of HLA alleles and cytochrome P450 (CYP) alleles with dapsone-induced SCAR in Thai non-leprosy patients. A prospective cohort study, 16 Thai patients of dapsone-induced SCARs (5 SJS-TEN and 11 DRESS) and 9 Taiwanese patients of dapsone-induced SCARs (2 SJS-TEN and 7 DRESS), 40 dapsone-tolerant controls, and 470 general Thai population were enrolled. HLA class I and II alleles were genotyped using polymerase chain reaction-sequence specific oligonucleotides (PCR-SSOs). CYP2C9, CYP2C19, and CYP3A4 genotypes were determined by the TaqMan real-time PCR assay. We performed computational analyses of dapsone and DDS-NHOH interacting with HLA-B*13:01 and HLA-B*13:02 alleles by the molecular docking approach. Among all the HLA alleles, only HLA-B*13:01 allele was found to be significantly associated with dapsone-induced SCARs (OR = 39.00, 95% CI = 7.67-198.21, p = 5.3447 × 10-7), SJS-TEN (OR = 36.00, 95% CI = 3.19-405.89, p = 2.1657 × 10-3), and DRESS (OR = 40.50, 95% CI = 6.38-257.03, p = 1.0784 × 10-5) as compared to dapsone-tolerant controls. Also, HLA-B*13:01 allele was strongly associated with dapsone-induced SCARs in Asians (OR = 36.00, 95% CI = 8.67-149.52, p = 2.8068 × 10-7) and Taiwanese (OR = 31.50, 95% CI = 4.80-206.56, p = 2.5519 × 10-3). Furthermore, dapsone and DDS-NHOH fit within the extra-deep sub pocket of the antigen-binding site of the HLA-B*13:01 allele and change the antigen-recognition site. However, there was no significant association between genetic polymorphism of cytochrome P450 (CYP2C9, CYP2C19, and CYP3A4) and dapsone-induced SCARs (SJS-TEN and DRESS). The results of this study support the specific genotyping of the HLA-B*13:01 allele to avoid dapsone-induced SCARs including SJS-TEN and DRESS before initiating dapsone therapy in the Asian population.

Adverse effects of polychemotherapy for leprosy in 13 years of follow-up at a university hospital

Abstract Leprosy is one of the neglected diseases in the world and Brazil is the second country with more cases. A retrospective study was conducted based on the medical records of 196 leprosy patients diagnosed during the course of 13 years at a university hospital. The aim was to describe the adverse effects of polychemotherapy, as well the most prevalent and most vulnerable populations. In the study, dapsone was the most implicated drug, especially in women, and the risk increased with age. The authors conclude that with this patient profile, greater vigilance should be taken regarding possible adverse effects, especially anemia.

Mycobacterium leprae: aspectos da resistência aos fármacos na poliquimioterapia / Drug resistance in multidrug therapy for Mycobacterium leprae

Introdução: O diagnóstico da hanseníase possui números significativos que causam preocupação à saúde pública. Os casos de resistência medicamentosa nessa doença se iniciaram em meados dos anos 60 e diante do problema, a Organização Mundial da Saúde instituiu em 1981 a poliquimioterapia, associação dos antibióticos rifampicina, dapsona e clofazimina, tratamento atual de escolha. A resistência aos fármacos na hanseníase é reportada pela literatura, desvelando um obstáculo à sua eliminação. Apresentamos nessa revisão os principais aspectos da resistência medicamentosa no tratamento para hanseníase e seus impactos. Metodologia: Revisão sistemática sobre os aspectos da resistência medicamentosa utilizando a pesquisa exploratória como metodologia de abordagem. Foram pesquisados os termos resistência medicamentosa, hanseníase, recidiva, alterações genéticas e os operadores booleanos "and" e "or" na busca. Resultados e discussão: A dificuldade de tomar a medicação corretamente foi um dos principais fatores que acarretaram resistência do bacilo Mycobacterium leprae aos fármacos. Homens de países norte e sul-americanos e asiáticos foram os mais atingidos por episódios de resistência. A resistência medicamentosa é uma das principais causas de recidivas em hanseníase. O principal fármaco causador de resistência medicamentosa descrito nos trabalhos foi a dapsona (46,6%) e a maioria das alterações genéticas encontradas estão no gene rpoB; 23,2% dos registros relatados foram de resistência secundária aos fármacos e, também, sete casos de resistência múltipla a esses medicamentos. Conclusão: Os principais aspectos da resistência medicamentosa na hanseníase são os equívocos ao ingerir os medicamentos e as alterações genéticas na bactéria. Os impactos causados estão na dificuldade de refazer o tratamento, a possibilidade de nova transmissão e o aparecimento de sintomas mais graves.

Introduction: The diagnosis of leprosy has significant numbers causing public health concern. Reports of drug resistance in this disease begun in the mid-1960s and due to this problem, the World Health Organization instituted a multidrug therapy with rifampicin, dapsone, and clofazimine antibiotic association in 1981, which is currently the first-choice treatment for leprosy. Cases of drug resistance have been reported in literature, revealing an obstacle to the eradication of the disease. This paper has the purpose of presenting the key aspects and impacts of drug resistance in the treatment for leprosy. Methods: Systematic review of the drug resistance aspects using exploratory research as an approach methodology. The authors searched the terms drug resistance, leprosy, recurrence, genetic alterations, and the Boolean operators "and" and "or" between them. Results and discussion: The difficulty in taking the medication correctly was one of the key factors that led to drug resistance for Mycobacterium leprae. Men from North and South American, as well as from Asian countries, were the most affected by episodes of resistance. Drug resistance is one of the main causes of leprosy recurrences. Dapsone was the most frequently identified drug resistance in the studies (46.6%), while most of the genetic alterations were found in the rpoB gene; 23.2% of the cases were from secondary resistance episodes, and seven cases of multiple resistance were reported. Conclusion: The misconceptions when taking the treatment and the Mycobacterium leprae genetic alterations have been described as the key aspects of drugs resistance in leprosy and the impacts caused are the difficulty in redoing the treatment, the possibility of new transmission, and the appearance of more severe symptoms.

Adverse effects of polychemotherapy for leprosy in 13 years of follow-up at a university hospital.

Leprosy is one of the neglected diseases in the world and Brazil is the second country with more cases. A retrospective study was conducted based on the medical records of 196 leprosy patients diagnosed during the course of 13 years at a university hospital. The aim was to describe the adverse effects of polychemotherapy, as well the most prevalent and most vulnerable populations. In the study, dapsone was the most implicated drug, especially in women, and the risk increased with age. The authors conclude that with this patient profile, greater vigilance should be taken regarding possible adverse effects, especially anemia.

Dapsone-induced hepatic complications: it's time to think beyond methemoglobinemia.

Drug-induced liver injury is an important cause of hepatotoxicity and poses a challenging clinical problem with respect to both diagnosis and management. Patients susceptible to hepatotoxicity on exposure to dapsone is constantly on the rise. Dapsone (4,4'-diaminodiphenylsulfone) is clinically used alone or in combination with rifampicin for the treatment of a variety of dermatological disorders such as acne, dermatitis herpetiformis, psoriasis, Toxoplasma gondii infections, leprosy and pneumocystis carinii pneumonia in AIDS patients. However, the clinical use of dapsone is limited because of dose-dependent adverse hematological reactions. The cholestatic injury caused by dapsone and its N- hydroxylated metabolites hinders bile flow and causes oxidative stress and hepatic necrosis, further, leading to hemolysis responsible for hepatitis due to iron overload in the liver. Hence, clinicians' awareness of the hepatotoxic potential of dapsone is highly warranted.

Validation study of HLA-B*13:01 as a biomarker of dapsone hypersensitivity syndrome in leprosy patients in Indonesia.

Leprosy is a stigmatizing, chronic infection which degenerates the nervous system and often leads to incapacitation. Multi-drug therapy which consists of dapsone, rifampicin and clofazimine has been effective to combat this disease. In Indonesia, especially in Papua Island, leprosy is still a problem. Furthermore, there had been higher reports of Dapsone Hypersensitivity Syndrome (DHS) which also challenges leprosy elimination in certain aspects. Globally, DHS has a prevalence rate of 1.4% and a fatality rate up to 13%. The aim of this study is to validate HLA-B*13:01, a previously discovered biomarker for DHS in the Chinese population, as a biomarker for DHS in the Papua population.This is a case-control study of 34 leprosy patients who presented themselves with DHS (case subjects) and 52 leprosy patients without DHS (control subjects). Patients were recruited from 2 provinces: Papua and West Papua. DNA was extracted from 3 ml blood specimens. HLA-B alleles were typed using the gold-standard sequence based typing method. Results were then analysed using logistic regression and risk assessment was carried out. The results of HLA-typing showed that HLA-B*13:01 was the most significant allele associated with DHS, with odds ratio = 233.64 and P-value = 7.11×10-9, confirming the strong association of HLA-B*13:01 to DHS in the Papua population. The sensitivity of this biomarker is 91.2% and specificity is 96.2%, with an area under the curve of 0.95. HLA-B*13:01 is validated as a biomarker for DHS in leprosy patients in Papua, Indonesia, and can potentially be a good predictor of DHS to help prevent this condition in the future.

The HLA-B*13:01 and the dapsone hypersensitivity syndrome in Korean and Asian populations: genotype- and meta-analyses.

BACKGROUND: The human leukocyte antigen (HLA)-B*13:01 was reported as an important risk factor for dapsone hypersensitivity syndrome (DHS) in Chinese and Thai populations. RESEARCH DESIGN AND METHODS: From the Korean nationwide registry, seven subjects with previous DHS were included. Their HLA allele/phenotype frequencies were compared with 8 dapsone-tolerant subjects recruited from a single institution, and general population (n = 485) in Korea. The authors also performed a meta-analysis with these data using previous Chinese and Thai studies. RESULTS: Among the seven DHS subjects, 85.7% presented with the HLA-B*13:01 allele. The HLA-C*03:04, HLA-DRB1*12:02 (both in linkage disequilibrium with HLA-B*13:01), and HLA-A*02:01 alleles were also presented in 85.7%, 71.4%, and 71.4%, respectively. Subjects with HLA-B*13:01 were susceptible to developing DHS compared to dapsone-tolerant controls (odds ratio [OR]: 73.667) and the Korean general population (OR: 139.500). HLA-C*03:04 (OR: 40.935), HLA-DRB*12:02 (OR: 36.613), and HLA-A*02:01 (OR: 5.862) showed similar results. In meta-analysis, HLA-B*13:01 was associated with dapsone-induced hypersensitivity (overall OR: 42.692), and subgroup analyses according to the control types demonstrated similar results (OR:43.694 and 41.866, respectively). CONCLUSIONS: Similar to previous Asian population studies, HLA-B*13:01 is significantly associated with the risk of DHS in Korea. These associations may be useful for preventing DHS and improving drug safety.

A Case of Dapsone-induced Mild Methemoglobinemia with Dyspnea and Cyanosis.

Dear Editor, Dapsone is a dual-function drug with antimicrobial and antiprotozoal effects and anti-inflammatory features (1). In dermatology, it is a first choice for conditions such as leprosy, IgA pemphigus, dermatitis herpetiformis, and linear IgA bullous dermatosis, or an adjunctive treatment for, e.g. bullous pemphigoid (BP) and pemphigus vulgaris (1). However, dapsone is associated with some adverse effects, including methemoglobinemia (1). Methemoglobin (MetHb) concentrations of less than 15% usually cause no symptoms in patients with normal hemoglobin concentrations (2). Herein, we report the case of a patient with BP who developed dyspnea because of dapsone-induced methemoglobinemia that was as mild as 4.7%. A 93-year-old man was diagnosed with BP based on skin manifestations (Figure 1, a and b), histopathological findings (Figure 1, c and d), and anti-BP180 NC16A antibody titer determined by chemiluminescence enzyme immunoassay (279 U/mL) 3 years earlier. His comorbidities included diabetes mellitus, chronic heart failure, right pleural effusion, and brain infarction. The patient had been successfully treated with oral prednisolone, so the steroid was tapered to 4 mg/day. The blisters recurred, however, and new ones kept developing even though the prednisolone was increased to 25 mg/day. Dapsone (75 mg/day) was begun as adjunctive treatment, and new blister formation ceased. At one week from dapsone initiation, the patient developed dyspnea, and his oxygen saturation as measured by pulse oximetry decreased to 88% on room air. At presentation, his blood pressure was 118/78 mmHg, the heart rate was 95 beats/minute, and axillary temperature was 36.3 °C. Neurological examination and consciousness findings remained unchanged compared with findings before dyspnea onset. Chest examination showed normal breath and heart sounds, but lip and peripheral cyanosis was present. Blood tests revealed a white blood cell count of 12,920/µl; red blood cells, 370×104/µl; hemoglobin, 11.7 g/dl; and CMV antigenemia (or C7-HRP), negative. Chest CT and echocardiography indicated no remarkable change compared with imaging from one year earlier. Arterial blood gas analysis showed a pH of 7.454, PaO2 63.1 mmHg, PaCO2 35.4 mmHg, HCO3- 24.3 mmol/L, SaO2 92.4%, and MetHb of 4.7%. These findings indicated a saturation gap (difference between SpO2 and SaO2) induced by MetHb. Upon cessation of dapsone, MetHb levels and SpO2 returned to normal and the dyspnea resolved, implicating dapsone in the methemoglobinemia (Figure 1, e). Differential diagnoses were pulmonary disease, heart disease, neuromuscular disease, sepsis, and drug intoxication. These possibilities were ruled out by the physical examination, drug history, vital signs, blood tests, and chest CT and echocardiography. In normal individuals, MetHb levels are less than 1% (2). Healthy patients with normal hemoglobin concentrations develop cyanosis at MetHb level of 15-20%, dyspnea at 20-50%, and coma at 50-70%, and die at more than 70% (2). However, patients with hematologic disease, acidosis, or cardiopulmonary diseases, for example, present with symptoms even with MetHb levels less than 15% (2,3). We inferred that our patient presented with dyspnea even under mild methemoglobinemia because he had anemia, chronic heart failure, and right pleural effusion. The occurrence of dapsone-induced methemoglobinemia with obvious symptoms is rare (1,4). Clinicians should be aware that methemoglobinemia symptoms are influenced not only by MetHb concentrations but also by comorbidities.