A 40-year-old man comes to the office due to a month of progressively worsening burning and tingling sensations in the hands and feet. He works building outdoor fences but recently has had difficulty handling heavy tools. The patient has no medical issues and takes no medications. He does not use tobacco or alcohol. Blood pressure is 100/70 mm Hg, and pulse is 70/min. The skin over the neck has patchy areas of hyperpigmentation and hypopigmentation. Hyperkeratoses and scaling are present on the palms and soles. There is increased sensitivity to pinprick and light touch over the fingers and toes. Plantarflexion and dorsiflexion are weak at the ankle, and there is weakness of the interossei and wrist flexors and extensors. Upper and lower limb deep tendon reflexes are 1+. Laboratory results are as follows: Which of the following is the most likely diagnosis for this patient?

Question

A 40-year-old man comes to the office due to a month of progressively worsening burning and tingling sensations in the hands and feet.  He works building outdoor fences but recently has had difficulty handling heavy tools.  The patient has no medical issues and takes no medications.  He does not use tobacco or alcohol.  Blood pressure is 100/70 mm Hg, and pulse is 70/min.  The skin over the neck has patchy areas of hyperpigmentation and hypopigmentation.  Hyperkeratoses and scaling are present on the palms and soles.  There is increased sensitivity to pinprick and light touch over the fingers and toes.  Plantarflexion and dorsiflexion are weak at the ankle, and there is weakness of the interossei and wrist flexors and extensors.  Upper and lower limb deep tendon reflexes are 1+.  Laboratory results are as follows:  Which of the following is the most likely diagnosis for this patient?

Quizplus · Accepted Answer

11ec25c8_d494_7a1d_bc81_630b625afcd1_MD0003_00 This patient, who is routinely exposed to pressure-treated wood through building outdoor fences, has polyneuropathy, pancytopenia, mild transaminase elevation, and a variety of skin lesions characteristic of chronic arsenic toxicity. Arsenic is a metalloid element that exists in numerous forms, including both natural and manmade compounds. Although humans are often exposed to low levels through diet and water, toxic exposure is more likely through mining, pesticide manufacturing, metalworking, and working with pressure-treated wood (eg, used in outdoor fences) preserved with arsenic. Arsenic binding to sulfhydryl groups and interfering with various enzymes is likely responsible for the clinical manifestations of acute and chronic arsenic toxicity. Patients chronically exposed to arsenic develop a sensorimotor neuropathy in a stocking-glove distribution with burning, painful hypersensitivity, distal weakness, and hyporeflexia. Hypo- and hyperpigmentation of the skin occurs early in arsenic toxicity, and hyperkeratosis and scaling of the soles and palms is often seen later. Mees lines (horizontal striation of fingernails) are characteristic. Acute, severe arsenic toxicity can lead to profound pancytopenia and hepatitis, and chronic exposure leads to these manifestations to a smaller degree. Diagnosis is made through history, physical examination, and measurement of urine arsenic levels. Chelation (eg, dimercaprol, dimercaptosuccinic acid) is the treatment of choice for severe toxicity. (Choice B) Guillain-Barré syndrome presents with progressive motor neuropathy and decreased/absent deep-tendon reflexes. However, it is not typically associated with hypersensitivity to tactile sensation, skin changes, or liver enzyme abnormalities. (Choice C) Acute intermittent porphyria is caused by a partial deficiency of porphobilinogen deaminase, an enzyme involved in heme synthesis. Acute attacks are triggered by a number of factors and are associated with patchy sensorimotor neuropathy and autonomic dysfunction. However, severe abdominal pain is typical, and skin involvement or cytopenias are rare. (Choice D) Chronic lead poisoning can lead to sensorimotor neuropathy in a stocking-glove distribution along with microcytic anemia. Although the neuropathy is similar to arsenic toxicity, gastrointestinal complaints are typical and skin changes are not usually seen. (Choice E) Vitamin A deficiency is associated with xerophthalmia (pathologic eye dryness), night blindness, follicular hyperkeratosis (rather than on palms and soles), and immunity impairment. It is rare in developed countries and not generally associated with polyneuropathy. (Choice F) Vitamin B₁₂ deficiency can lead to macrocytic anemia, loss of position and vibration sensation, ataxia, spasticity, and incontinence. It is not associated with liver enzyme abnormalities or hyporeflexia. The skin changes seen in this patient are also more suggestive of arsenic toxicity. Educational objective: Arsenic toxicity should be suspected in a patient with possible environmental exposure (eg, pressure-treated wood, pesticides) who has painful sensorimotor polyneuropathy, skin lesions (hypo- and hyperpigmented, hyperkeratotic), pancytopenia, and mild transaminase elevation. Diagnosis is confirmed with elevated urine arsenic levels. References: The broad scope of health effects from chronic arsenic exposure: update on a worldwide public health problem. (http://www.ncbi.nlm.nih.gov/pubmed/23458756)

A 40-Year-Old Man Comes to the Office Due to a Month