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Case 75. Diphtheria (68 y-o M)
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Pseudomembrane formed in the throat in a patient with fatal dyspnea
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Key words : Corynebacterium diphtheriae, pseudomembrane
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| The pharyngeal squamous mucosa is densely covered with faintly basophilic material (pseudomembrane). Moderate submucosal inflammation is seen here (HE). | Another view of the pharyngeal mucosa demonstrates thick pseudomembrane attachment and relatively mild inflammatory reaction (HE). | |
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| Numbers of large-sized Gram-positive rods are embedded within the pseudomembrane (Gram). | Scanning electron micrograph of a club-shaped rod without flagella or capsule, being consistent with the Corynebacterium species ("coryne" means club). | |
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| Cultured Corynebacterium diphtheriae (Neisser stain) Metachromatic granules, stained black-brown, are seen at one end or both ends of the rods. The pathogenicity of C. diphtheriae is determined by diphtheria toxin production. |
Non-pathogenic Corynebacterium in conjunctival mucosa (Quick Giemsa) Club-shaped, large-sized rods are often seen in a Y or V-shaped (non-parallel) arrangement. Non-diphtherial Corynebacteria are non-pathogenic, and are distributed in the oral cavity, skin, conjunctiva and vagina as normal flora. |
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