Methemoglobinemia due to malachite green ingestion in a child

Abstract

Malachite green is a commercially available dye used to treat parasitic and fungal disease in fish. No previous reports of human injury could be located from acute ingestion of malachite green. We report a case of methemoglobinemia of 51% in a 3 year old girl after acute ingestion of malachite green from a commercially available aquarium product.

Keywords: :

• Malachite green
• Methemoglobin
• Poisoning

Introduction

Malachite green, (4-(4-Dimethylaminobenzhydriylidene) cyclohexa-2,5-dienylidene) dimethylammonium chloride (CAS 569-66-2) is an aniline dye used to treat parasitic and fungal disease in fish and as a biological stain in cell and tissue cultures. An electronic search of MEDLINE for the years 1950 through January 2007 located no published reports of human injury from acute ingestion of malachite green. We report what we believe is the first case of methemoglobinemia after ingestion of malachite green

Case report

A 3-year-old healthy, 17.3 kg, girl with no previous significant medical history was discovered by her father with blue lips and nail beds after ingesting up to two ounces of an aquarium product containing 0.075% malachite green (45 mg) (ICK Away by Wardley®). The ingestion was observed by two older siblings (6 and 8 years of age). By history no other ingestants were available and the cyanosis was first recognized approximately 30 minutes post ingestion. In the emergency department she was awake, and crying with generalized cyanosis, including blue head, hands, arms, feet, and legs. Initial vital signs were heart rate 115 bpm, respirations 30/min, and temperature 98.2° F (36.8° C). An initial arterial blood gas was reported as pH 7.43, pCO2 22.9 mmHg, pO2 57.7 mmHg, HCO3 15 mmol/L, O2 saturation 47.4%, methemoglobin (MetHb) 50.6%. An infusion of methylene blue was begun at 2 mg/kg and the patient responded rapidly by becoming pink. A repeat MetHb level 2½ hours post ingestion was 6.5%. The empty 2 ounce aquarium product container was brought to the emergency department for visual inspection. The child was transferred to a regional pediatric intensive care unit and observed for 20 hours without return of symptoms.

Discussion

Malachite green has a number of commercial uses and is primarily available in two forms, as malachite green and the reduced form leucomalachite green. It is a popular treatment against the protozoan disease Ich (Ichthyophthirius) and the the fungus Saprolegnia in freshwater aquaria. It is in this formulation that our patient had access to it.

Malachite green was formerly used in commercial aquaculture against the fungus Saprolegnia which infects fish eggs. The reduced form of malachite green, (Leucomalchite green) accumulates in fish tissue and based on rat feeding studies has been determined to be a carcinogen (1–4). Another common commercial use for malachite green is as a biological stain for microscopic analysis of cell and tissue samples. Finally, the reduced form of malachite green, lecucomalachite green (LMG), has been used as a detection method for latent blood in criminalistics (5,6).

We could locate no previous reports of methemoglobinemia after ingestion of malachite green. However, malachite green is reduced to the more stable form LMG, by normal intestinal flora (1). In smaller amounts, normally associated with exploratory behavior in small children, intestinal flora activity may be sufficient to reduce the available MG to LMG prior to absorption. In our case the large amount ingested may have exceeded the initial capacity of the intestinal flora to reduce the MG to LMG, leaving sufficient MG to be absorbed in its more reactive state. Additionally malachite green is a derivative of aniline, a potent hemoglobin oxidizer and known producer of methemoglobinemia.

In summary, we report what we believe is the first case of methemoglobinemia in a previously healthy 3-year-old girl after ingestion of malachite green from a commercially available aquarium product.

Notes

3. National Toxicology Program. Toxicology and carcinogenesis studies of malachite green chloride and leucomalachite green. (CAS NOS. 569–64–2 and 129–73–7) in F344/N rats and B6C3F1 mice (feed studies). National Toxicology Program Technical Report Series 2005; (527):1–312.