Acute Otitis Media (AOM): This is the most common cause of ear pain and fever in children, especially in the 3-year-old age group. The symptoms of AOM include ear pain, fever, irritability, and sometimes a decrease in appetite. The diagnosis is typically made clinically, with confirmation by otoscopy showing a bulging tympanic membrane.

Upper Respiratory Tract Infection (URTI): Often presents with fever and can cause ear pain due to Eustachian tube dysfunction leading to middle ear effusion without infection.
Otitis Externa: An infection of the outer ear canal, which can cause significant pain and fever, especially if the canal is swollen shut.
Pharyngitis: Can cause referred ear pain, especially if the pharyngitis is caused by a bacterial pathogen like Group A beta-hemolytic streptococcus.

Mastoiditis: A serious complication of AOM where the infection spreads to the mastoid bone. It presents with fever, ear pain, and signs of mastoid bone involvement such as swelling behind the ear.
Lateral Sinus Thrombosis: A rare but potentially life-threatening complication of AOM or mastoiditis, where a blood clot forms in the lateral sinus.
Intracranial Complications of Otitis Media: Such as brain abscess, subdural empyema, or meningitis, which are rare but can be fatal if not promptly diagnosed and treated.

Relapsing Fever: Caused by Borrelia species, transmitted by ticks or lice, which can cause fever and ear pain among other symptoms.
Autoimmune Disorders: Such as Juvenile Idiopathic Arthritis (JIA), which can cause fever and ear pain due to temporomandibular joint involvement or middle ear effusion.
Tuberculous Otitis Media: A rare cause of ear infection, especially in areas with high tuberculosis prevalence, which can present with chronic ear discharge, fever, and ear pain.