Which of the following post-infectious complications of diphtheria typically develops in the 2nd to 3rd week of illness and is characterized by cranial nerve palsies followed by ascending paralysis?

Explanation

## Late Neurologic Complication: Diphtheric Neuropathy **Key Point:** Diphtheric neuropathy is a post-infectious complication that develops in the 2nd–3rd week of illness, characterized by demyelination and ascending paralysis. It begins with cranial nerve involvement and may progress to involve peripheral nerves and respiratory muscles. **Pathophysiology:** - Diphtheria toxin damages myelin sheaths of peripheral nerves - Causes demyelination (similar to Guillain-Barré syndrome but distinct) - Toxin-mediated injury to Schwann cells - Results in conduction block and paralysis **Clinical Presentation:** - **Early (1st week):** Soft palate paralysis (nasal voice, difficulty swallowing) - **2nd–3rd week:** Cranial nerve palsies (CN IX, X, XI, XII) - **Later:** Ascending paralysis (limb weakness, respiratory muscle involvement) - **Recovery:** Usually complete over weeks to months **Clinical Pearl:** - Occurs even with appropriate antitoxin and antibiotic therapy - Distinct from myocarditis (which occurs earlier, in 2nd week) - May require mechanical ventilation if respiratory muscles are involved - Prognosis is generally good with supportive care **High-Yield:** The combination of **late onset (2nd–3rd week) + cranial nerve involvement + ascending paralysis** is pathognomonic for diphtheric neuropathy. **Mnemonic:** **DIPHTHERIA complications by timing:** - **Week 1:** Pseudomembrane, toxic symptoms - **Week 2:** Myocarditis (early) - **Week 2–3:** Neuropathy (late), cranial nerve palsies - **Week 3+:** Ascending paralysis