A 11-year-old boy presented with increasing left sided pain below his ear for 4 days along with high grade fever. There was some nasal congestion over the last 3 weeks due to high pollen counts. The pain has worsened despite taking decongestants and acetaminophen. The patient is a known case of allergic rhinitis and has had multiple episodes of otitis media in the past. On examination, there is tenderness and swelling of the left mastoid process and fluid behind the left temporal membrane. CT scan of the concerned region was done. Which of the following is the most likely diagnosis: –

**Core Concept**
The patient's symptoms and examination findings suggest an acute infection of the mastoid process, which is an extension of the middle ear. This condition is often associated with a history of otitis media, and the patient's known case of allergic rhinitis may have contributed to the development of Eustachian tube dysfunction.

**Why the Correct Answer is Right**
The patient's presentation is classic for acute mastoiditis, which occurs when an infection of the middle ear extends to the mastoid process. This can happen when the middle ear infection is not properly treated, leading to the spread of bacteria to the mastoid air cells. The patient's symptoms of increasing pain, fever, and swelling of the mastoid process are consistent with this diagnosis. The fluid behind the left temporal membrane is likely due to the spread of infection to the mastoid cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while otitis media is a possible complication of allergic rhinitis, it does not directly explain the patient's symptoms of mastoiditis.

**Option B:** This option is incorrect because while Eustachian tube dysfunction can contribute to the development of otitis media, it is not a direct cause of mastoiditis.

**Option C:** This option is incorrect because while the patient's symptoms may suggest a complication of otitis media, the specific diagnosis of mastoiditis is more likely given the patient's examination findings and history.

**Clinical Pearl / High-Yield Fact**
Acute mastoiditis is a medical emergency that requires prompt treatment with antibiotics and possibly surgical drainage. It is essential to consider this diagnosis in patients with a history of otitis media who present with symptoms of mastoiditis, such as pain and swelling of the mastoid process.

**Correct Answer:** C. Acute mastoiditis.

✓ Correct Answer: A. Acute mastoiditis