For clinical purposes, a considerable phylogenetic relationship exists among all stinging species, so
that the clinical features of the coelenterate syndrome are fairly constant, with a spectrum of severity. This is
related to the season and species (venom potency and configuration of the nematocyst), the number of
nematocysts triggered and the size of the animal (venom inoculum), the size and age of the victim (the very
young and old and the smaller person tend to be more severely affected), the location and surface area of the
sting, and the health of the victim. The wise clinician suspects a coelenterate envenomation in all unexplained
cases of collapse in the surf, diving accidents, and near drownings. Any victim in distress pulled from marine
waters should be carefully examined for one or more cutaneous lesions that may provide the clue to a
coelenterate envenomation.
Mild envenomation may result only in an annoying dermatitis, whereas severe envenomation can progress
rapidly to involve virtually every organ system, resulting in significant morbidity and mortality. Clinical
envenomation is described here by severity, with the understanding that there is a fair amount of overlap.
Mild Envenomation
The stings caused by the hydroids and hydroid corals, along with lesser envenomations by Physalia,
Velella vellela, Drymonema dalmatinium (stinging cauliflower), Olindias sambaquiensis (endemic to Blanca
Bay area south of Buenos Aires province), scyphozoans, and anemones, result predominantly in skin
irritation. There is usually an immediate pricking or stinging sensation, accompanied by pruritus, paresthesias,
burning, throbbing, and radiation of the pain centrally from the extremities to the groin, abdomen, and axillae.
The area involved by the nematocysts becomes red-brown-purple, often in a linear whiplike fashion,
corresponding to tentacle prints. Other features are blistering, local edema, angioedema, and wheal formation,
as well as violaceous petechial hemorrhages. The papular inflammatory skin rash is strictly confined to the
areas of contact and may persist for up to 10 days. Areas of body hair appear to be somewhat more protected
from contact than hairless areas. If the envenomation is slightly more severe, the aforementioned symptoms,
which are evident in the first few hours, can progress over a course of days to local necrosis, skin ulceration,
and secondary infection. This is particularly true of certain anemone (Sagartia, Actinia, Anemonia,
Actinodendron, and Triactis) stings. A painless "jellyfish sting," in which there is a pattern of hyperpigmented
linear streaks, might represent the occurrence of phytophotodermatitis (e.g., from citrus juice spilled on skin
and later exposed to light).
Untreated, the minor to moderate skin disorder resolves over 1 to 2 weeks, with occasional residual
hyperpigmentation for 1 to 2 months. Rubbing can cause lichenification. Local hyperhidrosis, fat atrophy, and
contracture may occur. Facial swelling with sterile abscess formation has been reported. Permanent scarring
or keloids may result. Persistent papules or plaques at the sites of contact may demonstrate a predominantly
mononuclear cell inflammatory infiltrate, which may represent a delayed hypersensitivity response to an
antigenic component of the coelenterate nematocyst or venom. This may be accompanied by localized
arthritis and joint effusion. It has been suggested that sensitization may occur without a definite history of a
previous sting, since coelenterates may release antigenic and allergenic venom components into the water.
Granuloma annulare, which is usually both a sporadic and a familial inflammatory dermatosis, has been
associated with a Physalia utriculus envenomation. Gangrene has been observed.
Moderate and Severe Envenomation
The prime offenders in this group are the anemones, Physalia species, and scyphozoans. The skin
manifestations are similar or intensified (as with Chironex) and are compounded by the onset of systemic
symptoms, which may appear immediately or be delayed by several hours:
1. Neurologic: malaise, headache, aphonia, diminished touch and temperature sensation, vertigo, ataxia,
spastic or flaccid paralysis, mononeuritis multiplex, Guillain-Barrč syndrome, parasympathetic dysautonomia,
plexopathy, radial-ulnar-median nerve palsies, brainstem infarction (not a confirmed relationship), delirium,
loss of consciousness, convulsions, coma, and death
2. Cardiovascular: anaphylaxis, hemolysis, hypotension, small artery spasm, bradyarrhythmias (including
electromechanical dissociation and asystole), tachyarrhythmias, vascular spasm, deep venous thrombosis,
congestive heart failure, and ventricular fibrillation
3. Respiratory: rhinitis, bronchospasm, laryngeal edema, dyspnea, cyanosis, pulmonary edema, and
respiratory failure
