Removal of this membrane reveals a bleeding edematous submucosal tissue. The membrane may be localized or extend widely, forming a cast of the pharynx and the tracheobronchial tree. Soft tissue edema of the airways can compromise respiratory function, and death by suffocation from soft tissue edema and aspiration of the membrane is common. The neuropathy usually occurs 2-6 weeks after infection, but it may be delayed for up to 3 months after primary infection. Children younger than 10 years more commonly are affected.
Diphtheria begins as a respiratory infection with strident coughing and fever.
In the eye, conjunctival infection may be mild, resembling a viral conjunctivitis with preauricular adenopathy, palpebral and bulbar conjunctival erythema and edema, and a moderate amount of yellowish discharge. However, the more typical diphtheric infection is that of membranous conjunctivitis. Infiltration of the conjunctival surface leads to extreme edema and erythema of the eyelids with increasing stiffness of the lids. Membrane formation occurs over both the palpebral and bulbar conjunctivae, and the membrane ultimately becomes necrotic and sloughs off, leaving behind severe conjunctival scarring with formation of symblepharon, entropion, trichiasis, and disturbances of tear production. The conjunctiva may become necrotic, and thrombosis of perilimbal vessels can lead to corneal ulceration and scarring and to corneal perforation from corneal ischemia.