A 32-year-old man from Delhi presents with a 2-week history of sustained fever, abdominal pain, and rose spots on the trunk. Blood culture grows Salmonella typhi. Which clinical feature best distinguishes typhoid fever caused by S. typhi from paratyphoid fever caused by S. paratyphi?

## Distinguishing Typhoid from Paratyphoid Fever ### Clinical Comparison | Feature | S. typhi (Typhoid) | S. paratyphi (Paratyphoid) | |---------|-------------------|---------------------------| | **Severity** | More severe, higher mortality | Milder, shorter course | | **Intestinal complications** | Perforation (1–3%), necrosis common | Rare perforation (<0.5%) | | **Duration** | 3–4 weeks untreated | 1–2 weeks, shorter | | **Rash (rose spots)** | Present in ~5% | Less common | | **Hepatosplenomegaly** | Common | Common | | **Relative bradycardia** | Present | Present | | **Blood culture positivity** | ~80% in week 1 | ~80% in week 1 | ### Key Point: **Intestinal perforation is the hallmark complication that distinguishes typhoid from paratyphoid.** S. typhi causes deeper ulceration of Peyer's patches, leading to transmural necrosis and perforation in 1–3% of untreated cases. S. paratyphi causes superficial mucosal inflammation with perforation in <0.5%. ### High-Yield: S. typhi is responsible for the classic enteric fever syndrome with higher morbidity and mortality. Paratyphoid is a milder illness with faster resolution and fewer complications. ### Clinical Pearl: Rose spots, hepatosplenomegaly, and relative bradycardia occur in **both** typhoid and paratyphoid. These are NOT discriminating features. The key difference is the **depth of intestinal invasion** — S. typhi penetrates to the submucosa and muscularis, whereas S. paratyphi remains superficial. ### Warning: **Do not confuse "rose spots present" with "typhoid."** Rose spots are rare (5%) and can occur in paratyphoid too. Their absence does not rule out either disease.