A 28-year-old man developed a pruritic, nonhealing rash after brushing his hand and leg against coral while snorkeling in the British Virgin Islands. The patient did not notice any stinging or pruritus and found no foreign material in the abrasion.
During the ensuing nine days, however, the areas became inflamed, pruritic and tender. He denied fever or other systemic symptoms. Erythematous, pruritic papules surrounded a large abrasion on his right lateral calf, and similar papules were noted on the dorsal aspect of his right hand. Palpation of the calf detected diffuse induration of the affected area but elicited only mild tenderness.
The patient had reactive lymphadenopathy in the right groin and slight lymphadenopathy of the right popliteal chain. No purulence was observed in either area. Can you make the correct diagnosis?
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The patient had a rare form of contact dermatitis caused by cnidarian envenomation that occurred when he brushed against the coral reef.
The main organism in most coral reef systems is the stony or true coral. Each coral polyp is a tubular saclike animal with a central mouth surrounded by a ring of tentacles. Thousands of these genetically identical polyps form a coral head and secrete calcium carbonate, which serves both as exoskeleton and backbone of the reef.
The coral’s tentacles contain nematocysts, or cnidocysts, specialized venom-filled cells containing a hollow, coiled, threadlike structure with a barbed tip used to trap and immobilize prey. A hairlike sensor, the cnidocil, projects from the outer surface of the nematocyst. Mechanical and chemical stimulation of the cnidocil causes the nematocyst to fire rapidly. The barbed thread is thrust into the prey’s skin, resulting in envenomation.
The stony coral belongs to the invertebrate phylum Cnidaria, from the Greek word cnidos, which means “stinging needle.” Cnidarians are broken into four main classes: anthozoans (sea anemones, corals), hydrozoans (hydroids, fire coral, Portuguese man-of-war), scyphozoans (jellyfish, sea nettles) and cubozoans (box jellyfish).
The clinical manifestations of cnidarian envenomation range from a mild dermatitis to death within 30 to 60 seconds (box jellyfish). Symptoms vary with species according to venom potency, nematocyst configuration, the organism’s size, the volume of venom delivered, and the size, age and underlying health of the victim.
The first symptom to develop after contact with a coral is pain, either from nematocyst discharge, physical trauma or both. Erythema and pruritus usually follow.
Given the appearance and location of this patient’s rash, the diagnosis was almost certainly contact dermatitis (whether allergic or irritant), but the differential with regard to the inciting agent is endless. Without the patient’s report, there would be no reason to suspect coral reef dermatitis, unless the physician was practicing in a coral-rich area. Clearly, the history is crucial and a diagnosis would not be made by physical appearance or symptomatology alone.
In addition to the risk of envenomation, physical contact with a coral reef can result in abrasions and lacerations, as experienced by our patient. Wounds can become superinfected with marine organisms, including Vibrio, Aeromonas, Erysipelothrix, Bacteroides, and Pseudomonas species, streptococci, salmonella, Escherichia coli, Chromobacterium violaceum, Clostridium perfringensand Mycobacterium hemophilum.
Although mild cellulitis is the most likely infectious manifestation, more severe infections do occur, including one reported case of necrotizing fasciitis following a minor penetrating injury from a coral reef.1 A case of dermographism following laceration from a coral reef has also been described.2
Treatment of cnidarian stings begins with removing any visible foreign material because nematocysts can continue to fire, even after being separated from the organism, exacerbating the victim’s pain. Acutely, soap and water should be used to scrub cuts and abrasions, followed by normal saline irrigation to remove foreign material. A brief rinse with acetic acid may inactivate the nematocysts, reducing the stinging sensation.
Wounds may require surgical debridement and, if infected, oral antibiotics that cover common organisms associated with marine trauma. If a dermatitis develops, as happened in our patient, oral and/or topical steroids can be prescribed.
The patient was given oral steroids as well as clobetasol and mupirocin ointments to be applied to all wounds twice daily. After one week, both his hand and his leg showed signs of healing and less inflammation. The oral steroids were stopped, but he continued to use the topical medications.
At his final visit, both areas appeared to be nearly healed, and there were no signs of inflammation. The patient reported only mild pruritus in the affected areas. He was taken off the topical medications and told to use a menthol-camphor anti-itch lotion and return on his own recognizance. He has not returned, and we presume there were no further problems.
By Erin E. Ducharme, MD; Wil Tutrone; and Robin Buchholz, MD.
1. Gomez JM, Fajardo R, Patiño JF et al. “Necrotizing fasciitis due to Vibrio alginolyticus in an immunocompetent patient.” J Clin Microbiol. 2003;41:3427-3429.
2. Wu JJ, Huang DB, Murase JE et al. “Dermographism secondary to trauma from a coral reef.”
J Eur Acad Dermatol Venereol. 2006;20:1337-1338.