How should a child who ingested a naphthalene-containing mothball be evaluated and managed, particularly regarding hemolysis, methemoglobinemia, and possible glucose‑6‑phosphate dehydrogenase deficiency?

Naphthalene Ball Ingestion in a Child

Immediate Management Priority

A child who ingests a naphthalene mothball requires immediate assessment for hemolysis and methemoglobinemia, with G6PD testing performed urgently before any methylene blue administration, as G6PD deficiency dramatically worsens outcomes and contraindicates standard antidote therapy. 1, 2, 3

---

Initial Clinical Assessment

History and Physical Examination Focus

• Document the exact timing of ingestion (symptoms typically emerge 1–4 days post-exposure) and estimate the amount ingested. 4, 5, 6
• Obtain detailed family history for G6PD deficiency, particularly in children of Mediterranean, African, Asian, or Southeast Asian descent—this single question can be life-saving if laboratory results are delayed. 2, 3
• Assess for clinical signs of hemolysis: jaundice, dark urine (hemoglobinuria), pallor, tachycardia, and lethargy. 4, 5, 6
• Evaluate for methemoglobinemia: cyanosis (especially perioral or acral), chocolate-brown blood that does not turn red with oxygen exposure, and altered mental status despite normal oxygen saturation on standard pulse oximetry. 1

---

Essential Laboratory Evaluation

Immediate Testing Panel

• Co-oximetry methemoglobin level (not standard pulse oximetry, which is unreliable for detecting methemoglobinemia). 1
• Complete blood count with reticulocyte count to assess degree of hemolysis and bone marrow response. 4, 5, 6
• Comprehensive metabolic panel including blood urea nitrogen and creatinine (naphthalene causes acute renal failure). 4, 7
• Lactate dehydrogenase, total and direct bilirubin, and haptoglobin to quantify hemolysis severity. 5, 6
• Urinalysis to detect hemoglobinuria. 4, 7
• Peripheral blood smear for Heinz bodies and bite cells (characteristic of oxidative hemolysis). 1, 7

Critical Pre-Treatment Screening

• G6PD quantitative assay must be sent immediately, but recognize that results during acute hemolysis may be falsely elevated due to reticulocyte predominance—repeat testing 50–120 days later is essential for definitive diagnosis. 3
• Do not wait for G6PD results before initiating supportive care, but absolutely avoid methylene blue until deficiency is ruled out. 2, 3, 8

---

Treatment Algorithm Based on Methemoglobin Level and G6PD Status

Supportive Care (All Patients)

• Aggressive IV hydration with isotonic crystalloid to maintain renal perfusion and prevent acute tubular necrosis from hemoglobinuria. 1, 8, 4
• Supplemental oxygen to maximize oxygen delivery despite impaired hemoglobin function. 1, 8
• Ensure adequate glucose availability (via IV dextrose if needed) because endogenous reducing enzymes and methylene blue both require glucose-derived NADPH to function. 1, 8
• Monitor for multi-organ dysfunction: hepatic transaminases, creatine kinase (rhabdomyolysis), and serial renal function. 4, 7

Methylene Blue Decision Tree (G6PD Status Unknown or Normal)

Treat with methylene blue 1–2 mg/kg IV over 3–5 minutes if: 1, 8

• Methemoglobin ≥20% and symptomatic (cyanosis, altered mental status, dyspnea)
• Methemoglobin ≥30% even if asymptomatic
• Methemoglobin 10–30% with additional risk factors (anemia, cardiac/pulmonary disease, young age)

Repeat dosing: 1, 8

• If no improvement within 30–60 minutes, give second dose of 1 mg/kg IV
• Maximum cumulative dose is 7 mg/kg (higher doses paradoxically worsen methemoglobinemia)
• For prolonged naphthalene exposure, may require repeat dosing every 6–8 hours for 2–3 days

Alternative Therapy if G6PD Deficiency Confirmed or Suspected

Methylene blue is absolutely contraindicated in G6PD deficiency—it precipitates severe hemolytic anemia and paradoxically worsens methemoglobinemia. 1, 2, 3, 8

Use intravenous ascorbic acid instead: 2, 3, 8

• Dose: 0.5–10 g IV (exact pediatric dosing extrapolated from adult data; higher end for severe cases)
• Therapeutic effect requires 24 hours or longer (much slower than methylene blue)
• Monitor for hemolysis, as high-dose ascorbic acid can itself trigger hemolysis in G6PD deficiency, though the benefit outweighs risk in life-threatening methemoglobinemia

Adjunctive therapies: 4, 6

• N-acetylcysteine (standard acetaminophen overdose dosing) may provide antioxidant support
• Exchange transfusion for refractory cases or severe combined hemolysis and methemoglobinemia

---

Management of Hemolytic Anemia

Transfusion Thresholds

• Transfuse packed red blood cells for hemoglobin <7 g/dL or symptomatic anemia (tachycardia, hypotension, altered mental status). 4, 5, 6
• Naphthalene-induced hemolysis in G6PD-deficient children frequently requires transfusion (79% in one series). 9

Monitoring During Acute Phase

• Serial hemoglobin every 4–6 hours until hemolysis stabilizes (typically 48–72 hours post-exposure). 4, 5, 6
• Daily reticulocyte count to assess bone marrow response. 5, 6
• Urine output monitoring to detect acute kidney injury from hemoglobinuria. 4, 7

---

Critical Pitfalls to Avoid

G6PD Testing Errors

• Never interpret a "normal" G6PD level during acute hemolysis as excluding deficiency—young red cells have near-normal enzyme activity, masking the defect. 3
• Repeat quantitative G6PD testing 50–120 days after resolution to obtain accurate diagnosis. 3
• Screen first-degree relatives if deficiency is confirmed, as this is an X-linked disorder. 3

Methylene Blue Contraindications Beyond G6PD

• Pregnancy: teratogenic risk and fetal hemolysis. 2, 8
• Serotonergic medications (SSRIs, SNRIs, MAOIs): risk of serotonin syndrome due to methylene blue's monoamine oxidase inhibitory properties. 2, 8
• Renal failure: impaired clearance increases toxicity. 2

Delayed Presentations

• Naphthalene toxicity manifests 1–4 days post-ingestion, so a negative initial presentation does not exclude subsequent severe hemolysis or methemoglobinemia. 4, 5, 6
• Instruct families to return immediately for jaundice, dark urine, pallor, or respiratory distress. 5, 6

---

Disposition and Follow-Up

Admission Criteria

• All symptomatic children require PICU admission for continuous monitoring, as multi-organ failure (renal, hepatic, respiratory) can develop rapidly. 4, 7
• Asymptomatic children with documented ingestion require 24-hour observation given delayed toxicity. 5, 6

Outpatient Follow-Up

• Repeat G6PD quantitative testing at 3 months if initial testing was performed during acute hemolysis. 3, 4
• Counsel families on G6PD deficiency management if confirmed: avoid oxidant drugs (primaquine, dapsone, sulfonamides, rasburicase), fava beans, and naphthalene products. 3, 7
• Remove all naphthalene-containing mothballs from the home and replace with paradichlorobenzene alternatives (though these also carry toxicity risk). 9

---

Public Health Consideration

Naphthalene mothballs are used by 15–27% of households primarily for "fresh scent" rather than moth repellency, creating unrecognized risk in populations with high G6PD deficiency prevalence (2–13% in certain ethnic groups). 9 Anticipatory guidance during well-child visits should address this hidden household hazard.