Acute arsenical myopathy: morphological description

Mitochondrial myopathy caused by arsenic trioxide therapy

Arsenic trioxide (ATO) has been successfully used as a treatment for acute promyelocytic leukemia (APL) for more than a decade. Here we report a patient with APL who developed a mitochondrial myopathy after treatment with ATO. Three months after ATO therapy withdrawal, the patient was unable to walk without assistance and skeletal muscle studies showed a myopathy with abundant cytoplasmic lipid droplets, decreased activities of the mitochondrial respiratory chain complexes, multiple mitochondrial DNA (mtDNA) deletions, and increased muscle arsenic content. Six months after ATO treatment was interrupted, the patient recovered normal strength, lipid droplets had decreased in size and number, respiratory chain complex activities were partially restored, but multiple mtDNA deletions and increased muscle arsenic content persisted. ATO therapy may provoke a delayed, severe, and partially reversible mitochondrial myopathy, and a long-term careful surveillance for muscle disease should be instituted when ATO is used in patients with APL.

Rhabdomyolysis: a review

Rhabdomyolysis, a syndrome of skeletal muscle breakdown with leakage of muscle contents, is frequently accompanied by myoglobinuria, and if sufficiently severe, acute renal failure with potentially life-threatening metabolic derangements may ensue. A diverse spectrum of inherited and acquired disorders affecting muscle membranes, membrane ion channels, and muscle energy supply causes rhabdomyolysis. Common final pathophysiological mechanisms among these causes of rhabdomyolysis include an uncontrolled rise in free intracellular calcium and activation of calcium-dependent proteases, which lead to destruction of myofibrils and lysosomal digestion of muscle fiber contents. Recent advances in molecular genetics and muscle enzyme histochemistry may enable a specific metabolic diagnosis in many patients with idiopathic recurrent rhabdomyolysis.

Treatment and toxicokinetics of acute pediatric arsenic ingestion: danger of arsenic insecticides in children

OBJECTIVES

To describe the toxicokinetics and management of acute pediatric arsenic ingestion.

DESIGN

Case report and literature review.

SETTING

Tertiary pediatric intensive care unit, St. John's Children's Hospital, Springfield, IL.

PATIENT

A 22-month-old boy ingested approximately twice the estimated lethal dose of arsenic trioxide (As(2)O(3)) ant bait. Only one household arsenical insecticide is available in the United States and is presumed to be shielded from human exposure. He survived without detectable sequelae. Initially, the patient developed signs of acute hemodynamic compromise with tachycardia, hypertension, gastrointestinal symptoms, and poor urine output. He became lethargic with muscle weakness and was somnolent but never developed encephalopathy, seizures, or late onset peripheral neuropathy.

INTERVENTIONS

He was stabilized with fluid resuscitation, placed on a sodium bicarbonate intravenous drip, and treated with intramuscular dimercaprol (British anti-Lewisite), 5 mg/kg every 6 hrs for 3 days. When the British anti-Lewisite and the sodium bicarbonate drip were discontinued, oral meso 2,3-dimercaptosuccinic acid (Succimer) was administered three times a day for 5 days and thereafter twice daily until the urine arsenic concentration decreased below 50 microg/L.

MEASUREMENTS AND MAIN RESULTS

Continuous monitoring in the pediatric intensive care unit included continuous electrocardiogram, arterial blood pressure, urine output, vital signs, arterial blood gases, serum and urine arsenic concentrations, electrolytes, electromyography, and determination of arsenic toxicokinetics. The child's serum arsenic concentration was the highest ever reported with survival.

CONCLUSIONS

Recovery from arsenic poisoning was attributable to the restoration and maintenance of adequate cardiac output and renal perfusion in early shock, which allowed depot intramuscular British anti-Lewisite to circulate and eliminate the poison. Although an intravenous antiarsenical chelating agent would be advantageous in treating shock from arsenic poisoning, none is currently available. We urge the immediate use of British anti-Lewisite therapy on patient presentation with suspected toxic arsenic ingestion.