Case presentation
A 44-year-old woman was vacationing on Aruba in the southern Caribbean Sea with her spouse. They explored a partially submerged plane wreck near Renaissance Island, snorkeling approximately 50 m away from their shore entry. She was equipped with a mask and snorkel, but no fins. Water conditions offshore were rougher than anticipated, and waves pushed them close to portions of the wreck that were just below the surface. She began kicking harder to swim away from the wreck, and the dorsum of her right foot struck a submerged piece of the wreck. Because of the rough waters, she disregarded inspecting the injury at the time in favor of reaching shore.
Once back on shore, she remembered having kicked the wreck. On self-examination, she found several very small abrasions near the first and second metatarsophalangeal joints on the dorsum of her right foot. There was no pain, swelling, or difficulty ambulating. The foot was covered in a clear, slimy film that she wiped away. Four days later, the abrasion sites became pruritic. A red, scaly, raised rash with curvilinear features appeared (Figure 1), including what appeared to be the letter “S” that blanched under pressure (Figure 1, inset). She had no systemic symptoms and no history of marine allergies or dermatitis. Because the patient worked in a hospital with a Hyperbaric and Undersea Medicine Department, she sought a medical opinion from colleagues.
Right foot 4 days after kicking the submerged wreck. A raised, white-red and scaly rash with a curvilinear aspect appeared within the area of the original abrasions. A portion of the rash randomly resembled the letter “S” just proximal to the first metatarsophalangeal joint, and blanched under pressure (inset).
What was the diagnosis, and how would you have treated this patient?
Diagnosis
Submerged saltwater wrecks are likely to be covered in coral over time. Several features of the patient’s history support the hypothesis of contact between coral and her skin, including having kicked a piece of a submerged wreck, finding a mucinous deposit on her skin once ashore, and delayed onset of a pruritic, raised, curvilinear red rash. Thus, the patient’s colleagues made a diagnosis of coral dermatitis.
Differential diagnosis
Differential diagnostic considerations included cellulitis, allergic dermatitis, accidental or self-inflicted trauma, sea-bather’s eruption, 1 marine animal attack, and cutaneous larva migrans. However, the diagnosis of coral dermatitis best fit the patient’s history, including contact with a submerged structure and the mucinous deposit it left behind. We also had the benefit of first seeing her on day 4, with no evidence of her being systemically unwell, but with localized pruritus and rash consistent in appearance with coral dermatitis. 2
Pathophysiology
Dermatitis can develop after physical contact with one of many coral species that produce toxic mucinous exudate and nematocysts.1,3 The ensuing rash appears over a period of minutes to days, possibly due to a hypersensitivity reaction. 2 The pattern imprinted on the skin is random, according to the pattern of the coral, with no underlying meaning to the “S” shape observed here.
Clinical course
The patient kicked the wreck on day 0, and the rash first appeared on day 4. The rash was restricted to the area of abrasion. On day 5, treatment with triamcinolone 0.1% ointment applied 2 to 3 times daily to the affected areas was initiated (Figure 2). By day 6, the rash began to stabilize in appearance and had partially receded (Figure 3). Day 7 brought partial relief of pruritus and further recession of the rash (Figure 4). By 2 weeks after initiation of steroids, both rash and pruritus had completely resolved. At no stage did she develop systemic symptoms, and at 4 months later her foot remained normal.
Right foot on day 5. The rash became more apparent, and topical steroid treatment was initiated.
Right foot on day 6. The raised curvilinear rash began to recede.
Right foot rash on day 7. Continued resolution of rash appearance.
Discussion
Aquatic activities expose outdoor enthusiasts to a wide variety of dermatologic risks. 1 ,4,5 Despite recognition that the state of the sea was becoming unsafe, contact with coral still occurred in our patient. Such contact may lead to abrasions and deposition of a mucinous exudate and nematocysts. 3 Washing the affected skin with vinegar or applying cold packs may help remove or neutralize unfired nematocysts. 1 However, if a rash consistent with coral dermatitis develops, the treatment of choice is topical steroid.1,2 Patients should be counseled to seek further medical attention if the initial rash worsens despite steroid therapy or does not resolve within 2 weeks, if systemic symptoms develop, or if a delayed granulomatous rash appears.