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Posted by Dr. Sushrut Jangi December 14, 2012 12:27 AM
Your Differential Diagnosis:
Among the many answers submitted, many of you guessed the correct answer - lead poisoning. The first person to guess correctly was patches2. Congratulations! Almost as many people guessed lyme disease as an alternative diagnosis; other common responses included syphilis and diabetes.
In Massachusetts, many of us are familiar with Lyme Disease, a tick-borne illness that usually presents with the characteristic rash along with fatigue, headaches, muscle pain, and joint pain. Many readers felt this patient could have the later stages of lyme disease, which can present with nerve pain and arthritis. However, lyme disease is unlikely to cause hearing loss and digestive problems; foot drop would be a very rare presentation. Neurosyphilis can present in a variety of ways, but usually patients complain of meningitis - headaches and a stiff neck. Diabetes can present with a painful neuropathy as this patient describes - even when blood sugar levels are only in the pre-diabetes range. However, this patient's other symptoms and lab results suggest the leading diagnosis.
Mr. M, over a long time period, had developed hearing loss, memory problems, constipation, numbness and tingling in his feet, and foot drop. While some of these problems could be attributed to age, the simultaneous onset along with the more unusual symptoms in his feet suggested a possible unifying diagnosis. Foot drop, when it occurs on both sides of the body, suggests a systemic disease. Alongside the numbness and tingling, it suggests that Mr. M has a condition that is affecting his nerves, which we call neuropathy. Other than diabetes, other causes of neuropathy include alcohol (which he doesn't drink), or a vitamin B12 deficiency (his levels are normal). Other, more rare causes, may occur from toxic agents. In this situation, the doctor gathered an exhaustive history and found it remarkable for Mr. M's significant exposure to metals as a machinist - though his doctor ruled that out as a cause because he was long retired - and his interest in gun sports.
"I use regular shotgun shell bullets," Mr. M says. "As the BBs come out of the shotgun shells, you end up breathing in mist. And those pellets are made out of lead."
So his primary care physician checked his lead level with that extra blood test -- and it was sky high. "Ideally, lead levels in the blood should be less than 10 [mg/dL]," says Dr. Rose Goldman, a professor in the Department of Environmental Health at the Harvard School of Public Health. Mr. M's lead level was near 50.
Lead poisoning -- a condition that we often think of in children -- occurs in adults too. Frequently, symptoms develop chronically, especially in people with occupations or hobbies that expose them to lead over time. "Cities like Boston and Baltimore are full of old, wonderful buildings we like to renovate," Goldman says. "Construction workers who deal in demolition or who scrape bridges are exposed to old paints that contain high levels of lead." Other at-risk groups include plumbers, police officers, car mechanics, and gas station attendants. People who take Ayurvedic herbal medications, paint, remodel homes, or do pottery work can also be exposed. Symptoms of chronic lead poisoning may be vague. Commonly, patients present with abdominal pain, constipation, headaches, and trouble concentrating. They may develop nerve damage, such as wrist drop or foot drop, or even hearing loss. Gun ranges, especially indoor, may have poor ventilation systems and patrons may inhale lead; preparing bullets increases this risk.
"Even outdoor shooting ranges, where a lot of people stand in close quarters on hot, muggy days, can develop high levels of lead," Goldman continues. "People who shoot guns should always wash their hands afterward."
Since getting his test results back, Mr. M has stopped going to the range for now, until his levels come back down to normal. Already, they've dropped below 40. He is hoping his symptoms will get better. He has also told his friends to get tested, but they are resistant. "They don't want to stop shooting," he says, but hopefully they'll come around.
Do you have your own medical mystery? Send me a description of your own case and I will consider writing about it. E-mail me at firstname.lastname@example.org.
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About the authorSushrut Jangi is an internist at Beth Israel Deaconess Medical Center and an editorial fellow at The New England Journal of Medicine. More »
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