**Question:** The type of Diphtheria with highest mortality is -

A. Cardiac Diphtheria
B. Neuromuscular Diphtheria
C. Mucosal Diphtheria
D. Gastrointestinal Diphtheria

**Correct Answer:** **Cardiac Diphtheria: [A].**

**Core Concept:** Diphtheria is a severe respiratory illness caused by the bacterium Corynebacterium diphtheriae. It primarily affects the respiratory system, though other forms can manifest in the cardiovascular, neuromuscular, and gastrointestinal systems.

**Why the Correct Answer is Right:** Cardiac Diphtheria is the most fatal form of Diphtheria due to the bacterium's toxin production causing severe damage to the heart. The diphtheria toxin interferes with the production of acetylcholine at the neuromuscular junction, leading to respiratory muscle weakness, and decreased secretion of saliva, vomit, and tears. This allows the bacteria to grow in the respiratory tract, leading to respiratory distress.

**Why Each Wrong Option is Incorrect:**

- **Neuromuscular Diphtheria: [B]** has a lower mortality rate compared to Cardiac Dipheria due to the less severe respiratory involvement. The toxin primarily affects the neuromuscular junction, leading to muscle weakness but not severe respiratory distress.

- **Mucosal Diphtheria: [C]** involves the respiratory and gastrointestinal tracts, leading to mild respiratory symptoms and a lower mortality rate compared to Cardiac Diphtheria.

- **Gastrointestinal Diphtheria: [D]** affects the gastrointestinal system, leading to mild symptoms like nausea, vomiting, and diarrhea. It has a lower mortality rate compared to Cardiac Diphtheria due to the lack of severe respiratory involvement.

**Clinical Pearl:** The most important aspect of Diphtheria management is early diagnosis and administration of appropriate antibiotics (such as Penicillin, Ciprofloxacin, or Erythromycin) to limit the toxin production and prevent further damage. Additionally, supportive care, including oxygen therapy and mechanical ventilation, is crucial in managing severe respiratory distress.