Unexpected Primaquine‐Induced Hemolysis in a G6PD‐Normal Patient: A Case Report From Nepal

ABSTRACT

Primaquine, an antimalarial drug, is essential for preventing relapses of Plasmodium vivax. However, it poses a risk of hemolytic anemia, particularly in glucose‐6‐phosphate dehydrogenase (G6PD) deficient patients. This case report details a 27‐year‐old male with normal G6PD levels who developed hemolytic anemia following primaquine therapy for P. vivax malaria. Despite a normal quantitative G6PD analysis, the patient experienced a significant drop in hemoglobin, necessitating early discontinuation of the drug. This case highlights the potential for hemolysis in G6PD‐normal patients, underscoring the importance of close monitoring and the limitations of current G6PD screening methods.

Summary.

• Primaquine can induce hemolytic anemia even in patients with normal G6PD levels.

• Routine monitoring of hemoglobin and bilirubin is essential during treatment to detect early hemolysis, emphasizing the need for caution with primaquine use despite normal G6PD screening results.

1. Introduction

Primaquine (PQ) is an 8‐aminoquinoline drug that is used for malaria treatment and prophylaxis [1]. Primaquine is the key anti‐malarial drug that eliminates Plasmodium vivax hypnozoites and thus prevents relapses [1, 2]. In order to prevent relapse, P. vivax or P. ovale malaria in children and adults (except pregnant women, infants aged < 6 months, women breastfeeding infants aged < 6 months, women breastfeeding older infants unless they are known no to be G6PD deficient, and people with G6PD deficiency) are treated with a 14‐day course (0.25–0.5 mg/kg body weight daily) of primaquine in all transmission settings [3]. Though it is widely recommended, it is commonly not given to malaria patients because of its hemolytic toxicity in glucose‐6‐phosphate dehydrogenase (G6PD) deficient patients [4, 5]. Following primaquine drug therapy, the degree of hemolysis depends on the dose administered and the severity of the enzyme deficiency [6]. The exact definitions for severe or clinically significant primaquine‐associated hemolysis or hemolytic anemia are not established, and the diagnosis is based on a decrease in hemoglobin level and/or clinical manifestations [5]. WHO recommends G6PD activity assessment before administration of primaquine for radical cure [3]. No diagnostic method is applied in hospital settings in low‐resource settings to screen G6PD enzyme activity prior to antimalarial treatment and is usually detected during the course of primaquine therapy [7], when patients present to healthcare units with classical signs of hemolytic anemia [8]. The approach to safe primaquine therapy hinges upon the ability to test and confirm G6PD normal status, but the expensive technique, which demands good laboratory conditions and qualified technicians, restricts access to these tests [7, 9]. We present a case of hemolytic anemia following PQ treatment in an individual with quantitative G6PD analysis within the normal range.

2. Case Presentation

A 27‐year‐old male driver presented to the emergency department of College of Medical Sciences Teaching Hospital with the chief complaint of fever and fatigue for 7 days, accompanied by 3 episodes of vomiting over 4 days, along with pain over the epigastrium. The patient was asymptomatic until the onset of the fever, which was intermittent and associated with chills and rigor. According to the patient, the fever was higher in the evening around 5 p.m. and relieved in the morning. The maximum recorded temperature was 103°F.

Upon examination, the patient was alert and conscious. His blood pressure was 110/60 mmHg, measured on the right hand; respiratory rate—20 breaths/min; axillary body temperature—99.8°F; pulse—107 beats/min; and SpO2—96%. The liver and spleen were not palpable.

3. Investigation and Treatment

A provisional diagnosis of malaria was made. A rapid malaria antigen test revealed positive results for Plasmodium vivax, and serological tests for typhoid, dengue, scrub typhus, brucella, Leptospira, hepatitis, and HIV were negative. A blood sample was sent for G6PD analysis to a nearby laboratory. Laboratory investigations on the day of admission (Day 0) revealed normal hemoglobin levels (12.8 mg/dL), leukopenia (3370/mm³), thrombocytopenia (45,000/mm³), and a USG of the abdomen and pelvis revealed a few calculi in the lumen of the gallbladder, with one measuring 7 mm. He was admitted to the hospital and given IV paracetamol 1 g and IV pantoprazole. He was also started on Tab. Chloroquine 10 mg per kg (600 mg for 2 days and 300 mg on the third day) and Tab. Primaquine 0.25 mg per kg (15 mg for 14 days) as per the National Malaria Treatment Protocol 2019 [10].

On Day 1, the definitive diagnosis of Plasmodium vivax malaria was confirmed from a peripheral blood smear. Spectrophotometry showed a total G6PD activity of 8.4 U/g Hb, which is well within the normal range. Hemoglobin had dropped to 11.7 g/dL, but it was within the normal range for the treatment of malaria. Investigations revealed hyperbilirubinemia (4.2 mg/dL). The cytology report revealed normocytic normochromic anemia with thrombocytopenia. There were no signs of icterus. Primaquine continued. On Day 2, the lab results showed a decrease in hemoglobin (9.8 g/dL) and hyperbilirubinemia (4.2 mg/dL). On the same day, the laboratory results showed a platelet count of 197,000/mm³ and a total leukocyte count of 17,870/mm³, which were significantly elevated compared to admission levels. There was fever on examination, but the examination did not reveal overt signs of sepsis. The drop in hemoglobin was still within the normal limit, and since there were no clinical symptoms, PQ was continued. On Day 3, hemoglobin dropped further to 9.5 g/dL. PQ was withheld, and the patient was kept under close observation of his vital signs and further laboratory workup. The laboratory parameters improved from Day 4. A summary of the clinical and laboratory parameters over the course of therapy is presented in Table 1.

TABLE 1.

Clinical and laboratory parameters of patient during primaquine therapy over time.

	Day 0	Day 1	Day 2	Day 3	Day 4
Symptoms	Fever, vomiting, epigastric pain Fatigue	Fever with chills and rigor Fatigue	Fever	—	—
Signs	Tenderness over epigastrium	Tenderness over epigastrium	—	Pallor	—
Hemoglobin	12.8 g/dL	11.7 g/dL	9.8 g/dL	9.5 g/dL	9.6 g/dL
Platelets	45,000/cu mm	40,000/cu mm	1,97,000/cu mm	60,000/cu mm	73,000/cu mm
Bilirubin (Total)	1 mg/dL	4.3 mg/dL	4.2 mg/dL	—	1.5 mg/dL
Unconjugated Bilirubin	0.8 mg/dL	2.1 mg/dL	1.2 mg/dL	—	0.4 mg/dL
Conjugated Bilirubin	0.2 mg/dL	2.2 mg/dL	3.0 mg/dL	—	1.1 mg/dL
MCHC	32 g/dL	33.15 g/dL	30.6 g/dL	33.1 g/dL	36.9 g/dL
MCH	28.1 pg/cell	31.2 pg/cell	24.5 pg/cell	27.1 pg/cell	30.7 pg/cell
Protein	—	5.8 g/dL	6.6 g/dL	—
SGOT	80.6 IU/L	28.2 IU/L	60.0 IU/L	—	60 IU/L
SGPT	25.8 IU/L	27.2 IU/L	34.0 IU/L	—	56.0 IU/L
Leucocyte	3370/cu mm	6750/cu mm	17,870/cu mm	4690/cu mm	6400/cu mm
Primaquine exposure	15 mg	15 mg	15 mg	Discontinued
Chloroquine	600 mg	600 mg	300 mg

4. Outcome and Follow‐Up

The patient was discharged on Day 6 with Cefixime 400 mg BD and Doxycycline 100 mg BD for 7 days. On the day of discharge, he had a hemoglobin level of 10.7 g/dL. Genomic DNA sequencing of the G6PD gene could not be performed due to a lack of necessary infrastructure.

5. Case Discussion

Primaquine is a well‐established treatment for Plasmodium vivax but is known to carry a risk of hemolytic anemia, particularly in patients with G6PD deficiency. The World Health Organization (WHO) recommends screening for G6PD deficiency before starting primaquine therapy [3]. Previous studies have reported a small risk of hemolysis in patients with normal G6PD levels, with one study documenting a 0.3% (1/389) incidence of clinically significant hemolysis [11]. While there have been reports of hemolytic anemia in patients who tested negative for G6PD deficiency using rapid diagnostic tests (RDTs), this case is unique in that the patient's G6PD levels were quantitatively within the normal range [12]. This finding challenges the reliability of current laboratory screening methods and suggests that clinicians should exercise caution even when G6PD test results suggest a lower risk [11]. This case represents the first known instance of significant hemolytic anemia induced by primaquine in a patient with a normal quantitative G6PD analysis. Detailed monitoring was possible due to the patient being admitted to a tertiary care center. Daily hemoglobin levels were measured, allowing for the early identification of hemolysis and the timely discontinuation of primaquine after three doses. The occurrence of hemolytic anemia in this patient, despite a normal quantitative G6PD analysis, suggests that current screening methods may not be foolproof. It cannot be assumed that any G6PD field test has perfect sensitivity even in optimal laboratory settings [13]. In our case, differential diagnoses for acute hemolytic anemia, aside from G6PD deficiency, include undiagnosed enzymatic deficiencies such as pyruvate kinase or glutathione synthetase deficiency, and membrane disorders like hereditary spherocytosis. Hereditary spherocytosis was ruled out based on a normal peripheral blood smear, the absence of a family history of similar illnesses or gallstones, and the lack of a palpable spleen on examination. However, enzymatic deficiencies could not be excluded due to the unavailability of advanced diagnostic resources. Possible causes could include operator error during sample preparation and processing, cold chain issues that compromised the integrity of the sample or screening kit, or a lack of adequate climate control to ensure that tests were conducted under appropriate conditions.

On Day 2, the patient's persistent fever with leukocytosis raised concerns about a potential superimposed bacterial infection. Despite the absence of overt clinical signs of sepsis, the observed leukocytosis prompted the empirical initiation of cefixime and doxycycline. The differential diagnosis at the time included infection‐associated leukocytosis or reactive changes due to malaria treatment. Antibiotics were prescribed as a precautionary measure to address a possible bacterial component.

The delay in recognizing hemolysis in this case, due to the hemoglobin levels initially being within the expected range for anti‐malaria treatment, further emphasizes the need for better early markers of hemolytic anemia [11]. Identifying such markers could enable clinicians to make more informed decisions regarding the continuation of primaquine treatment quickly, thereby reducing the risk of severe hemolytic crises. Specific tests for acute hemolytic anemia, such as LDH and haptoglobin levels, were not conducted due to the lack of necessary resources and the financial burden they would impose on the patient. The patient did not show any physical signs and symptoms of anemia in the initial 3 days, and his urine color was normal even when his Hb dipped by almost 25% on Day 4. However, the presence of hyperbilirubinemia and a significant drop in hemoglobin levels during primaquine therapy strongly suggests hemolysis. Such absence of clinical signs and symptoms despite the significant decrease in hemoglobin suggests that there would be a substantial risk of delayed presentation to the hospital if this case were managed on an outpatient basis without proper follow‐up.

The National Malaria Treatment Protocol 2019 of Nepal encourages G6PD screening prior to the 14‐day PQ regimen, but it is notdone routinely because of a lack of necessary infrastructure, fears of additional costs, and a very low incidence of PQ‐induced severe hemolysis for a low‐dose PQ regimen provided over an extended period [10, 14]. This case shows that exposing patients to PQ treatment even after quantitative G6PD testing exposes patients to an increased risk of hemolysis. It underscores the need for clinicians to remain vigilant when prescribing primaquine at all levels of G6PD. It highlights the limitations of current G6PD testing and the importance of close monitoring for signs of hemolytic anemia. In settings where daily monitoring is not feasible, such as outpatient care in low‐resource environments, the risk of late presentation and severe anemia increases.

6. Conclusion

Hemolytic anemia is a significant complication associated with the use of primaquine. Therefore, screening for G6PD deficiency is essential before initiating primaquine therapy, and heightened vigilance is necessary even when G6PD levels are within the normal range on screening. There is a need for clearer instructions on how to detect signs of hemolysis.

Author Contributions

Aarju Khadka: writing – original draft, writing – review and editing. Sachet Subedi: writing – original draft. Nisha Lama: writing – review and editing. Indu Bhattarai: writing – review and editing. Chandrashekhar Deuba: writing – review and editing. Uttam Khatri: conceptualization, supervision. Nisha Regmi: supervision.

Ethics Statement

The authors have nothing to report.

Consent

Written informed consent was taken from patient for publication of the report.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

All the required data are available in the manuscript itself.