Background. Chronic sinusitis and its complications are common in patients with cystic fibrosis. Mucoceles are one of these complications and can have life-threatening consequences if left untreated.

Case. We present the case of a giant ethmoid mucocele leading to proptosis and hypertelorism in a 5-year-old child with cystic fibrosis.

Conclusion. Chronic sinusitis and its complications are common in patients with CF. Mucoceles are a rare complication of sinusitis that can be treated surgically. As seen in this case if left untreated mucoceles can lead to orbital pathologies such as proptosis, hypertelorism. To the best of our knowledge, we report the first case report of giant ethmoidal mucocele leading to proptosis and hypertelorism in a patient with cystic fibrosis.

Keywords: chronic sinusitis, cystic fibrosis, endoscopic sinus surgery, mucocele, proptosis