Comment
Manifestations of Mercury Poisoning
Dermatologic manifestations of mercury exposure are varied. The most common—allergic contact dermatitis—presents after repeat systemic or topical exposure.4 Mercury exanthem is an acute systemic contact dermatitis most commonly triggered by mercury vapor inhalation. It manifests as an erythematous maculopapular eruption predominantly involving the flexural areas and the anterior thighs in a V-shaped distribution.5 Purpura may be seen in severe cases. Cutaneous granulomas after direct injection of mercury also have been reported as well as cutaneous hyperpigmentation after chronic mercury absorption.6
Presentation of Pink Disease
Pink disease occurs in children after chronic mercury exposure. It was a common pediatric disorder in the 19th century due to the presence of mercury in certain anthelmintics and teething powders.7 However, prevalence drastically decreased after the removal of mercury from these products.3 Although pink disease classically was associated with mercury ingestion, cases also occurred secondary to external application of mercury.7 Additionally, in 1988 a case was reported in a 14-month-old girl after inhalation of mercury vapor from a spilled bottle of mercury.3
Pink disease begins with pink discoloration of the fingertips, nose, and toes, and later progresses to involvement of the hands and feet. Erythema, edema, and desquamation of the hands and feet are seen, along with irritability and autonomic dysfunction that manifests as profuse perspiration, tachycardia, and hypertension.3
Diagnosis of Pink Disease
The differential diagnosis of palmoplantar rash is broad and includes rickettsial disease; syphilis; scabies; toxic shock syndrome; infective endocarditis; meningococcal infection; hand-foot-and-mouth disease; dermatophytosis; and palmoplantar keratodermas. The involvement of the hands and feet in our patient, along with hyperhidrosis, tachycardia, and paresthesia, led us to believe that her condition was a variation of pink disease. The patient’s age at presentation (18 years) was unique, as it is atypical for pink disease. Although the polyarthropathy was attributed to Campylobacter, it is important to note that high levels of mercury exposure also have been associated with polyarthritis,8 polyneuropathy,4 and neuromuscular abnormalities on electromyography.4 Therefore, it is possible that the presence of these symptoms in our patient was either secondary to or compounded by mercury exposure.
Mercury Poisoning
Diagnosis of mercury poisoning can be made by assessing blood, urine, hair, or nail concentrations. However, as mercury deposits in multiple organs, individual concentrations do not correlate with total-body mercury levels.1 Currently, no universal diagnostic criteria for mercury toxicity exist, though a provocation test with the chelating agent 2,3-dimercaptopropanesulfonate is considered reliable in assessing total-body mercury burden.1
Elemental mercury, as found in some thermometers, dental amalgams, and electrical appliances (eg, certain switches, fluorescent light bulbs), can be converted to inorganic mercury in the body.9 Elemental mercury is vaporized at room temperature; the predominant route of exposure is by subsequent inhalation and lung absorbtion.10 Cutaneous absorption of high concentrations of elementary mercury in either liquid or vapor form may occur, though the rate is slow and absorption is poor. In cases of accidental exposure, contaminated clothing should be removed and immediately decontaminated or disposed. Exposed skin should be washed with a mild soap and water and rinsed thoroughly.10
The treatment of inorganic mercury poisoning is accomplished with the chelating agents succimer, dimercaptopropanesulfonate, dimercaprol, or D-penicillamine.1 In symptomatic cases with high clinical suspicion, the first dose of chelation treatment should be initiated early without delay for laboratory confirmation, as treatment efficacy decreases with an increased interim between exposure and onset of chelation.11 Combination chelation therapy also may be used in treatment. Plasma exchange or hemodialysis are treatment options for extreme, life-threatening cases.1
Conclusion
Mercury exposure should be included in the differential diagnosis of patients presenting with a rash on the palms and soles, especially in young patients with systemic symptoms. A high level of suspicion and a thorough history can prevent a delay in treatment and an unnecessarily extensive and expensive workup. An emphasis on early diagnosis and treatment is important for optimal outcomes and can prevent the severe and potentially devastating consequences of mercury toxicity.