Postvaccation Rash!!!!!!!

[unseennude]

A 34-year-old, otherwise healthy man presents to the emergency department with a chief complaint of a pruritic rash on the left lower part of his chest. The patient describes having swelling and pain at the same site 5 days earlier, but these symptoms have since disappeared. He denies having rashes elsewhere, exposure to new medications or foods, having insect or tick bites, or using new soaps or lotions. The patient recently returned from a vacation to a tropical region, where he was snorkeling. However, he cannot immediately recall any unusual exposures or injuries. He denies having fevers, wheezing, difficulty breathing, nausea, or upper respiratory symptoms.He had an immediate burning sensation and urticarial rash, which disappeared the next day. However, 5 days later, a pruritic, vesiculopapular rash appeared in the same location.



The patient has normal vital signs, and the physical findings are remarkable for only 2 distinct linear, erythematous, and vesiculopapular rashes on the left lower aspect of the chest wall (see Image).

What is the diagnosis?

Hint: the patient describes brushing up against an orange coral with his left torso.

[Oak]

Erythema Multiforme ho??? post vaccination rash is more common in VZV and small pox...

[unseennude]

Type IV delayed hypersensitivity reaction to fire coral: During detailed history taking, the patient describes brushing up against an orange coral with his left torso. He had an immediate burning sensation and urticarial rash, which disappeared the next day. However, 5 days later, a pruritic, vesiculopapular rash appeared in the same location (see Image).

Fire corals possess stinging cells known as nematocysts that become embedded in the dermis with a harpoon-like action and then envenomate the subject.

The venom released from the nematocyst causes a contact dermatitis characterized by an immediate but typically transient stinging sensation that ranges from mild to severe in intensity. Severe pruritus, vesiculation, urticaria, and necrosis are uncommon. Delayed contact hypersensitivity reactions may persist for days or, in rare cases, for months. The rash is usually self-limited and initially treated with the application of ice packs and analgesics. If recognized immediately after exposure, the site may be rinsed with ambient seawater followed by application of vinegar to prevent further nematocyst envenomation. To treat the delayed hypersensitivity rash or local pruritus, topical steroids are beneficial. Oral corticosteroids may be indicated to manage diffuse, severe, or persistent disease.

Type IV hypersensitivity reactions are cell-mediated inflammatory reactions that typically occur 48-72 hours after exposure to an antigen. Initiation of this type of reaction is by monocytes/macrophages and basophils. Infiltration by cytotoxic T cells and macrophages results in granuloma formation.

Delayed hypersensitivity reactions play an important role in the host's defense against intracellular pathogens. Important examples include (1) tuberculin skin reactions, in which individuals previously exposed to tuberculosis develop a reaction in the exposed area in 48-72 hours; (2) Jones-Mote hypersensitivity, which is characterized by a host response to a pure protein mixed with an adjuvant; (3) graft versus host disease, in which the body rejects the graft in a similar manner as it responds to the tuberculin antigen; and (4) contact hypersensitivity (eg, that caused by poison ivy or fire coral rash), which occurs when an antigen comes in contact with skin. This hypersensitivity is characterized by a largely basophilic infiltrate and eczematous- or vesicular-appearing rashes peaking 3-6 days after exposure.

For more information on hypersensitivity reactions to fire coral, see the eMedicine articles Cutaneous Manifestations Following Exposures to Marine Life (within the Dermatology specialty) and Coelenterate and Jellyfish Envenomations (within the Emergency Medicine specialty).