Al-Razi (Rhazes): First to Differentiate Measles and Smallpox

Rhazes: Pioneer of Differential Diagnosis

Muhammad ibn Zakariya al-Razi (Rhazes), 9th–10th century Persian physician, was the first to clinically distinguish measles from smallpox in his treatise Kitab al-Judari wa al-Hasbah.

Contributions

• Detailed symptom comparison (rash progression, fever pattern, complications).
• Early inoculation method (variolation) for smallpox.
• Emphasis on observation, case recording, empirical treatment.
• Authored Al-Hawi (Continens), a massive medical encyclopedia.

Legacy

Founder of pediatrics, ophthalmology; influenced medieval European medicine via Latin translations. His differential approach remains foundational.