Medical Mystery Solved — Hunting for a Diagnosis | NEJM

Summary

A 47-year-old man's mysterious illness was diagnosed as alpha-gal syndrome, an allergic reaction to red meat, likely caused by a lone star tick bite during hunting in Michigan. The case highlights the impact of climate change on the spread of ticks and the emergence of new allergies. The patient's recovery involved avoiding red meat and treatment with glucocorticoids and antihistamines.

Takeaways

• 🏥 Mr. A, a 47-year-old man, visited an emergency department with symptoms of faintness, swollen eyelids, itchy rash, and gastrointestinal issues, which could have various causes.
• 🔍 The potential unifying diagnosis for Mr. A's symptoms is mast cell activation, which can be triggered by environmental factors, food, medications, and underlying conditions like mastocytosis.
• 💊 Mr. A had a history of medical conditions including type 2 diabetes, kidney stones, and ADHD, and was taking medications including naproxen and an antacid for his symptoms.
• 🌡 His physical examination revealed a fast heart rate, low blood pressure, and hives, but no signs of infection or organ enlargement.
• 🧬 Laboratory tests showed an elevated white cell count, low serum sodium, reduced kidney function, high lactic acid, and elevated troponin and procalcitonin levels, indicating possible anaphylaxis or infection.
• 🚑 Mr. A's condition worsened with hypotension and tachycardia, suggesting anaphylaxis or septic shock, and he was treated with IV fluids, antibiotics, and medications to reduce histamine release.
• 🍽️ The patient's symptoms recurred after eating beef, and further questioning revealed a recent deer hunting trip, suggesting a new allergy to alpha-gal, a sugar found in nonprimate mammals.
• 🦟 Alpha-gal allergies are often caused by tick bites, particularly from the lone star tick, which has expanded its range due to climate change, affecting regions like southeastern Michigan where Mr. A resides.
• 🛑 Mr. A was diagnosed with alpha-gal syndrome, treated with glucocorticoids and antihistamines, and advised to avoid red meat to prevent further anaphylactic episodes.
• 🌡️ The case highlights the impact of environmental changes, such as climate change, on the prevalence of certain allergens and the importance for physicians to consider these factors in diagnosis.
• 📈 The patient's recovery and subsequent allergy testing confirmed the presence of alpha-gal IgE antibodies, emphasizing the role of environmental exposures in the development of new allergies.

Q & A

What were the initial symptoms that Mr. A presented to the Michigan emergency department with in January 2021?

Mr. A initially presented with feeling faint, swollen eyelids, an itchy rash, watery bowel movements without blood after eating, and over the following days, he experienced diffuse crampy abdominal pain, nausea, and occasional vomiting.

What is the potential unifying diagnosis that could explain all of Mr. A's symptoms?

The potential unifying diagnosis is the activation of mast cells, which mediate allergic reactions and can induce multiorgan symptoms through the release of histamine and other mediators.

What are some possible triggers for mast cell activation mentioned in the script?

Possible triggers for mast cell activation include environmental exposures, food, medications, and underlying conditions that are associated with increased mast cell number, such as mastocytosis or mast-cell activation syndromes.

What is hereditary or drug-induced angioedema, and why is it an unlikely explanation for Mr. A's symptoms?

Hereditary or drug-induced angioedema is a condition that causes swelling under the skin. It is an unlikely explanation for Mr. A's hives and hypotension because it does not typically account for these specific symptoms.

What medical conditions did Mr. A have a history of, and what medications was he taking?

Mr. A had a history of type 2 diabetes, kidney stones, rapid heartbeat, high triglyceride levels, and ADHD. He was taking medications for these conditions and had started taking naproxen and an antacid for his abdominal symptoms.

What laboratory findings were consistent with infection or anaphylaxis in Mr. A.'s case?

Mr. A.'s white-cell count was very elevated and was mostly composed of neutrophils, which is consistent with infection or anaphylaxis. His serum sodium level was low, kidney function was reduced, and the lactic acid level was high, indicating inadequate tissue perfusion.

What is anaphylaxis, and how is it related to Mr. A.'s symptoms?

Anaphylaxis is a severe, potentially life-threatening allergic reaction that involves mast-cell activation and can be caused by various triggers such as foods, medications, or insect bites or stings. Mr. A.'s symptoms, rapid heart rate, and hypotension may point to anaphylaxis.

What treatment was administered to Mr. A. for his symptoms, and what was the outcome?

Mr. A. was given IV fluids, broad-spectrum antibiotics, H2 blockers, and glucocorticoids. He was also given epinephrine for possible anaphylaxis. After treatment, his heart rate slowed, blood pressure improved, and his symptoms abated considerably.

What is alpha-gal allergy, and how is it related to Mr. A.'s case?

Alpha-gal allergy is a condition where humans develop alpha-gal–directed IgE antibodies after exposure to alpha-gal from nonprimate mammals, leading to an allergic response to red meat. Mr. A.'s symptoms and recent deer hunting activity suggest he may have developed an alpha-gal allergy.

How did the lone star tick play a role in Mr. A.'s diagnosis, and what is its connection to climate change?

The lone star tick, which contains alpha-gal from mammals it has fed on, is the most common vector for alpha-gal exposure in humans in the U.S. Its expanded geographic range, attributed to climate change, may have led to Mr. A. being bitten and developing the allergy.

What was the final diagnosis for Mr. A., and what instructions were given for his condition?

Mr. A. was diagnosed with alpha-gal syndrome. He was discharged with tapering doses of glucocorticoids and antihistamines and was instructed to avoid red meat to prevent further episodes of anaphylaxis.