Case Based Learning for July 2025

An Unusual Cause of Urticaria

ER Presentation:  A 45 y/o female arrived by EMS because she was awoken while sleeping with abdominal pain, n/v, scattered hives and dyspnea. She felt lightheaded when ambulating but there was no syncope.

Pertinent negatives:  no fever, cough, chest pain, throat pain or swelling in throat. Denied possible allergen exposure.

Past medical history: noncontributory.

Medications: none recently.

Allergies: None known

Social: no tobacco, alcohol or recreational drugs use.

Physical exam: Vitals: Afebrile, HR 120 and regular, BP 100/70, RR 20 and mildly labored, O2 sat 97% RA

Gen: Anxious-appearing female in mild respiratory distress.

Skin: Classic urticarial lesions on back, legs and arms. HEENT: Normal.

Neck: No adenopathy, thyromegaly, tenderness or swelling. Lungs: Wheezing in all fields with prolonged expiratory phase, no rales.

CV: RRR, mild tachycardia, no audible murmurs or rubs. Puerperal pulses present in all extremities, 3 over 4 in intensity.

Abdomen: Normal BS, nontender without masses or HSM.

Medical decision making: This healthy patient appears to be having an allergic reaction and will need to be observed especially in view of the dyspnea, light headedness at home and soft BP with tachycardia on arrival to the ER. She is awake and alert, has no lip or tongue swelling, but angioedema is in the differential. Working diagnosis: allergic reaction, cause unknown.

Differential diagnosis: the cause of hives is broad, hives with wheezing is usually caused by an exposure to an allergen, but other entities or processes must be considered. Such as:

Scombroid: Caused by consuming fish containing scombroid (histamine fish poisoning) such as tuna, mackerel, mahi-mahi, and blue fish that are not properly refrigerated. Bacteria in these fish can produce high levels of histamine and thus as allergic type reaction. Serum Sickness: A type 3 (immune complex) hypersensitivity, seen in conditions such as acute hepatitis B, infection and after certain medications (antibiotics, NSAIDs, biologics, and antidepressants). May occur within 1 to 2 days after exposure but more typically 1 to 2 weeks associated with fever and arthralgias. Alpha-gal syndrome: This rare syndrome occurs after a tick bite sensitizes the patient, causing an allergic reaction after eating red meat or other mammalian products even milk.

Treatment: The patient is having mild respiratory distress associated with wheezing and urticaria, her BP is only mildly low, and she is not in shock. Treatment instituted was IV NS bolus, antihistamines, nebulized albuterol and IV steroids, since the patient was not in shock epinephrine was not needed.

At this point no further diagnostic studies are indicated but a more through history was obtained: questions that needed to be asked were: what did she have for dinner, any new medications including OTC, any new exposures such as soaps, lotions, laundry products, onset of any joint pain or swelling, any  risk factors for hepatitis B, any tick bites or exposures? The patient states she had steak for super and dislikes fish, otherwise all questions were negative, except she was at her brother’s ranch in northeastern Oklahoma about 6 weeks ago and had a tick bite with a large local reaction which resolved w/o treatment.

The patient was observed after treatment and improved and discharged after discussion of alpha-gal syndrome as a probable cause. She was recommended to keep “an allergic reaction diary”. Discharge medications included oral antihistamines, albuterol MDI and EpiPen. She was cautioned to avoid red meat and associated food products known to cause alpha-gal syndrome since there is known cure and symptoms can recur for up to 5 years.

Alpha-gal Syndrome:  a food allergy acquired after the bite of the Lone Star tick. The tick tends to be in the southeastern United States (ARK, DE, TN, VA, Ind, MD, MI, MS, NC, OK) but the tick’s location is spreading towards north and west. The tick bite is typically associated with a large local reaction. The tick transfers a sugar molecule galactose alpha 1.3 (alpha-gal) making the patient allergic at a later date to red meat and mammalian products. Medical products derived from cows and pigs, for example heparin, antivenins, animal heart valves, monoclonal antibodies may also cause a reaction. Consumption of fish or poultry do not cause the reaction. 

In this patient a typical presentation of the syndrome with allergic manifestations of 2–6-hour onset, GI symptoms and other common allergic reaction symptoms. On occasion the reaction can be severe leading to death. n

In case of an anaphylactoid reaction an IgE level for alpha-gal could be sent.

TAKE HOME POINT: In the case of an allergic reaction of unknown cause add asking a question about prior tick bite exposure to your history.

Written by William Fialkowski  MD FACEP

ERx Clinical Partners Medical Director, Bacon County Hospital. Alma, GA

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This is for informational purposes only. For medical advice or diagnosis, consult a physician.

 

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