Chronic Rhinosinusitis with Nasal Polyps (CRSwNP): This is the most common condition associated with nasal polyps, characterized by chronic inflammation of the nasal and sinus mucosa, often linked to allergies, asthma, or environmental factors.

Allergic Fungal Sinusitis (AFS): A condition where nasal polyps are associated with an allergic reaction to fungi, often presenting with thick, eosinophilic mucin and fungal elements.
Samter's Triad: A syndrome consisting of aspirin sensitivity, asthma, and nasal polyps, which can lead to recurrent and severe nasal polyposis.
Cystic Fibrosis: Although more commonly associated with respiratory and gastrointestinal symptoms, cystic fibrosis can also lead to the development of nasal polyps due to the abnormal mucous production.

Invasive Fungal Sinusitis: A potentially life-threatening condition where fungal infection invades the nasal and sinus tissues, requiring prompt diagnosis and treatment.
Squamous Cell Carcinoma or Other Malignancies: Although rare, nasal polyps can be a presenting feature of sinonasal malignancies, emphasizing the importance of biopsy in atypical or resistant cases.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A systemic vasculitis that can present with nasal polyps among other symptoms, requiring early recognition to initiate appropriate treatment.

Primary Ciliary Dyskinesia (Kartagener Syndrome): A genetic disorder affecting ciliary function, leading to chronic sinusitis and potential development of nasal polyps.
Young's Syndrome: A condition characterized by obstructive azoospermia, chronic sinopulmonary infections, and nasal polyps, distinct from cystic fibrosis.
Nasal Polyps in the Context of Systemic Diseases (e.g., Sjögren's Syndrome, Relapsing Polychondritis): Various systemic diseases can have nasal polyps as part of their clinical presentation, though these are less common.