## Distinguishing Typhoid from Paratyphoid Fever ### Key Clinical Differences **Key Point:** Diarrhea is significantly more common in paratyphoid fever (S. paratyphi A and B), whereas typhoid fever (S. typhi) typically presents with constipation in the first 1–2 weeks, followed by possible diarrhea only in later stages. ### Comparative Features | Feature | Typhoid (S. typhi) | Paratyphoid (S. paratyphi A/B) | |---------|-------------------|--------------------------------| | **Fever pattern** | Stepladder (classic) | Stepladder (similar) | | **Rose spots** | Present in ~5–10% | Present in ~5–10% | | **Hepatosplenomegaly** | Common (60–70%) | Common (60–70%) | | **Gastrointestinal symptoms** | Constipation early; diarrhea late | Diarrhea prominent and early | | **Severity** | More severe, higher mortality | Milder, better prognosis | | **Duration** | 3–4 weeks untreated | 1–3 weeks untreated | **High-Yield:** The **predominance of diarrhea early in the illness** is the single best clinical discriminator between paratyphoid (diarrhea-prone) and typhoid (constipation-prone) fever. ### Why Other Features Are Not Discriminators **Clinical Pearl:** Rose spots, hepatosplenomegaly, and stepladder fever are present in BOTH typhoid and paratyphoid fever. They are features of enteric fever as a syndrome, not specific to either organism. **Warning:** Do not assume rose spots or hepatosplenomegaly distinguish the two — both are seen in both diseases. The GI symptom pattern is the key differentiator. ### Pathophysiologic Basis S. paratyphi A causes more mucosal inflammation and earlier intestinal involvement, leading to diarrhea. S. typhi causes more systemic toxemia with less early diarrhea, hence the classic "rose spots without diarrhea" presentation in early typhoid. [cite:Harrison 21e Ch 159]
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