Laboratory Studies
The following laboratory tests may be helpful:
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Culture and sensitivity of infected wounds: Consider cultures for atypical Mycobacteria (M marinum) in the presence of granulomatous and ulcerating lesions or sporotrichoid spread. Other test results usually are noncontributory, unless systemic reactions are noted.
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Intracutaneous tests with species-specific extracts: These can detect immediate and delayed-type reactions.
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Serologic tests: These may reveal elevated immunoglobulins directed against specific antigens in patients with delayed cutaneous manifestations.
Imaging Studies
Radiography is indicated to detect foreign body or involvement of deeper structures (eg, joint, bone).
Procedures
Consider taking a biopsy when diagnosis is in doubt or when tissue culture is indicated.
Histologic Findings
Histologic findings generally are nonspecific.
In seabather's eruption, superficial and deep perivascular and interstitial infiltrate consisting of lymphocytes, neutrophils, and eosinophils are described.
Biopsy of tissues infected with M marinum shows a mixed suppurative and granulomatous reaction with sparse-to-absent acid-fast bacilli.
Delayed skin reaction can be characterized by liquefaction degeneration of the basal layer.
Polarized light can reveal symmetric structures, corresponding to cross-sections of sea urchin spines.
Infections with V vulnificus show a nonspecific, yet characteristic, picture. Destruction extends into the dermis without an inflammatory cell infiltrate. Vasculitis may be present. Subepidermal noninflammatory bullae can be noted. Multiple organisms are observed.
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Mycobacterium marinum infection. Courtesy of the Department of Dermatology, UTMB at Galveston, Texas.
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Jellyfish stings. Courtesy of the Department of Dermatology, UTMB at Galveston, Texas.
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Erysipeloid. Courtesy of the Department of Dermatology, UTMB at Galveston, Texas.
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Envenomation caused by Portuguese-man-of-war. Courtesy of the Department of Dermatology, UTMB at Galveston, Texas.
