A 16-Month-Old Girl With Cough and Proteinuria

Melanie Malloy, MD, PhD; Sage W. Wiener, MD

Disclosures

December 10, 2015

Mercury accumulates in and is excreted by the kidneys and can cause nephrotic syndrome, with either underlying membranous nephropathy or minimal change disease. In one case series, many of the young children exposed to mercury were found to be hypertensive with no other cause for hypertension, highlighting a need to consider mercury toxicity in the differential diagnosis when young patients present with unexplained hypertension.[1] This is thought to be due to effects on the renin-angiotensin system.[7]

Acrodynia is a hypersensitivity reaction to mercury toxicity, characterized by pink discoloration and later desquamation of the hands and feet, irritability, leg cramping, and sweating. It is almost exclusively found in the pediatric population. In the early 20th century, it was much more common than today because calomel was an ingredient in teething remedies.

Exposure to elemental mercury is usually via inhalation of an aerosol, as very little elemental mercury is absorbed through the intact gastrointestinal tract. Elemental mercury is most typically aerosolized by attempts to vacuum up a broken thermometer (or another source of spilled elemental mercury). Elemental mercury vapor inhalation generally occurs in industrial settings. Acute large exposures result in metal fume fever, which presents as a flu-like febrile illness with nausea, fatigue, myalgias, arthralgias, and nonproductive cough. The inflammatory cascade can result in an acute respiratory distress-like clinical picture that can progress to respiratory failure and death. In this case, a subacute exposure to the fumes caused some of the respiratory manifestations, but they were not as severe as a larger, more acute exposure.

The primary means of exposure to organic mercury is through ingestion of large fish species such as shark and swordfish, which bioaccumulate mercury, mainly as methylmercury. People may also be exposed to organic mercury through industrial exposures to diethyl and dimethyl mercury, which are extraordinarily toxic in minute doses. Organic mercury is especially toxic when ingested because, of the three forms of mercury, it is the most easily absorbed into the gastrointestinal tract, with up to 90% absorbed into the bloodstream, and it is also the form that most easily enters the central nervous system.[8] The manifestations of organic mercury toxicity are primarily neurologic, including paresthesias, ataxia, visual disturbances, extremity numbness, and developmental delays in babies exposed in utero.

The differential diagnosis for respiratory disease and renal disease in a young child is wide. The specific constellation of symptoms in this case reflects the inhalational and dermal exposures to elemental and inorganic mercury afforded by the beauty cream.[9,10]

Coccidioidomycosis is endemic to northern Mexico. It usually presents with flulike symptoms and can manifest in the skin as erythema nodosum but does not cause the characteristic pink extremities of acrodynia. It also does not typically affect the kidneys as mercury toxicity does; however, in susceptible populations such as immunocompromised patients, hematogenous spread of Coccidioides can cause synovitis, osteomyelitis, and meningitis.

Kawasaki disease is an inflammatory vasculitis of young children that is characterized by prolonged fever, conjunctivitis, erythema of the oral mucosa, desquamation of the hands and feet, and lymphadenopathy. In Kawasaki disease, the desquamation usually follows the febrile phase, whereas in this patient, the hand and foot findings of acrodynia were concurrent with her other symptoms.

Berger disease, otherwise known as idiopathic immunoglobulin A (IgA) nephropathy, is a nephritic process usually associated with a preceding upper respiratory tract infection. Although proteinuria may be present in this disease, the more likely presentation is of recurrent gross hematuria.

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