A 16-year-old high school student gets a sudden burst of energy one spring day and decides to become a runner, joining her friends in a 2K fundraiser one Saturday morning. That night, she is quite sore; the next morning, she has so much pain in her shins she can hardly walk. Her mother suggests she apply ice packs to her legs, which she does, using elastic bandages to hold them in place for several hours, until the ice cubes melt.
As intended, the pain in her legs feels better. But as her legs rewarm, a rash appears where the ice packs contacted the skin. The itching and stinging are intense enough to alarm the girl’s mother, who calls and obtains a same-day appointment with dermatology. Topical diphenhydramine cream and calamine lotion, applied at home, are no help.
The area on each leg where the ice packs contacted the skin is covered by a solid orange-red wheal, the periphery of which is ringed by a faint whitish halo. There is no increase in warmth or tenderness elicited on palpation. No ecchymosis is seen, and the wheals are highly blanchable on deeper palpation. No other abnormalities of the skin are observed in this or other locations.
Clearly, this condition is urticarial in nature—albeit an unusual form, triggered by cold. Though it appears counterintuitive, cold uriticaria typically appears only on rewarming of the affected area, and is marked by the sudden appearance of “welts” or “hives” that usually clear (with or without treatment) within hours.
Uncomplicated urticaria resolves without leaving any signs (eg, purpura, ecchymosis) that might otherwise suggest the presence of a vasculitic component, such as that seen with lupus or other autoimmune diseases. Blanchability on digital pressure is one way to confirm benignancy, since blood tends to leak from vessels damaged by vasculitis, emptying into the surrounding interstitial spaces and presenting as nonblanchable petichiae, purpura, or ecchymosis.
The relatively benign nature of this patient’s urticaria was also suggested by additional history taking, in which she denied having fever, malaise, or arthralgia. These are all symptoms we might have seen with more serious underlying causes.
Cold urticaria is one of the so-called physical urticarias, a group that includes urticaria caused by vibration, pressure, heat, sun, and even exposure to water. Thought to comprise up to 20% of all urticaria, the physical urticarias occur most frequently in persons ages 17 to 40. Dermatographism is the most common form, occurring in the linear track of a vigorous scratch as a wheal that manifests rapidly, lasts a few minutes, then disappears without a trace. Its presence is purposely sought by the examiner to confirm the diagnosis of urticaria (most often the chronic idiopathic variety).
Primary cold urticaria (PCU), while usually localized and mild, can be accompanied by respiratory and cardiovascular compromise. Affected patients can develop fatal shock when exposed to cold water. Far more frequently, PCU is merely initially puzzling, then annoying. About 50% of patients with PCU see their condition cleared permanently after a few months, but the rest will experience periodic recurrences.
Besides avoidance of cold, PCU can be treated with antihistamines such as doxepin, cyproheptadine, or cetirizine. More stubborn, severe cases can be treated by desensitization: repeated, increased exposure to cold applied to increasing areas of the body over time. In cases where PCU is suspected but not seen, the clinician may apply ice to a small area of skin for 5 to 20 minutes, inducing a diagnostic wheal.
Secondary cold urticaria is associated with an underlying systemic disease, such as cryoglobulinemia, and patients are likely to experience symptoms such as headache, hypotension, laryngeal edema, and syncope. The ice-cube test is not advisable for these patients, lest tissue ischemia and vascular occlusion result.
Familial cold urticaria is also accompanied by systemic symptoms, as well as a positive family history and lesions with cyanotic centers and surrounding white halos. Referral of these atypical patients to allergy/immunology is mandatory.
TAKE-HOME LEARNING POINTS
1. Most forms of urticaria are uniquely evanescent (ie, they arise suddenly and resolve almost as quickly), leaving little if any residual skin changes.
2. The wheals of cold urticaria appear on rewarming of the area.
3. Wheals are also known as welts. The latter are often mistakenly termed whelps (which, according to the dictionary, refers to a puppy or kitten).
4. Cold urticaria is one of the so-called physical urticarias, other forms of which can be triggered by the pressure from shoes, heat, vibration, or even exposure to water.