Which of the following is a hallmark sign of allergic fungal sinusitis?

The hallmark sign of allergic fungal sinusitis is indeed the presence of sinus opacification with the accumulation of allergic mucin. This condition is characterized by an inflammatory response to fungal elements in the sinuses, leading to the production of thick, eosinophilic mucin. The accumulation of this mucin contributes to the characteristic opacification seen in imaging studies, often seen as a result of chronic inflammation and blockage of sinus drainage.

In allergic fungal sinusitis, the immunological response typically involves an elevated eosinophilic count and IgE production, which is crucial for the accumulation of this specific type of mucin. This distinguishes allergic fungal sinusitis from other forms of sinusitis, where the mucosal response and sinus involvement may present differently.

The correct identification of sinus opacification with allergic mucin is essential in diagnosing this condition, as it guides management and therapeutic interventions. Other options represent symptoms or signs that may be associated with different types of sinusitis or other sinus-related issues but do not specifically indicate allergic fungal sinusitis.