What is the primary disease affecting boys of Asian descent that presents with fever and symptoms including conjunctivitis and rash?

Kawasaki syndrome is a primary disease that predominantly affects boys of Asian descent, typically children under five years old. It is characterized by a constellation of symptoms, including prolonged fever, conjunctivitis, rash, cervical lymphadenopathy, and changes in the lips and oral cavity, such as strawberry tongue.

The fever in Kawasaki syndrome is usually high and lasts more than five days, which can lead to serious complications if not treated. The rash associated with Kawasaki syndrome is often polymorphous, and the conjunctivitis observed is usually bilateral and non-purulent. Recognizing these symptoms is crucial, as Kawasaki syndrome can lead to significant cardiac complications, including coronary artery aneurysms, if not promptly diagnosed and treated.

In contrast, the other conditions listed do not specifically fit the demographic profile or symptomatology associated with Kawasaki syndrome. Hypertrophic cardiomyopathy is a cardiac condition that doesn’t present with conjunctivitis or rash. Gastroenteritis primarily causes gastrointestinal symptoms, whereas simple fainting is not associated with the combination of fever, conjunctivitis, and rash. Thus, Kawasaki syndrome is the only condition that aligns with both the demographic and clinical presentation described in the question.