Differential Diagnosis
Single most likely diagnosis
- B) Mastoiditis: The symptoms of fever, irritability, and the specific findings of redness and tenderness behind the left ear, with the pinna displaced inferiorly and laterally, along with an immobile, erythematous, and bulging left tympanic membrane, are highly suggestive of mastoiditis. This condition is a complication of otitis media where the infection spreads to the mastoid bone.
Other Likely diagnoses
- C) Otitis externa: Although the primary symptoms point towards mastoiditis, otitis externa (swimmer's ear) could be considered due to the presence of redness and tenderness, especially if the patient has been exposed to water. However, the specific findings related to the tympanic membrane and the displacement of the pinna are more indicative of mastoiditis.
- D) Postauricular adenitis: This condition involves inflammation of the lymph nodes behind the ear and could present with similar symptoms of redness and tenderness in the postauricular area. However, it would not typically cause the specific tympanic membrane findings described.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- None specifically fit into this category as more dangerous alternatives that are less likely but critical to consider. However, it's essential to ensure that the diagnosis of mastoiditis is correct due to its potential complications, including intracranial spread of infection.
Rare diagnoses
- A) Cholesteatoma: This is a type of skin cyst located in the middle ear that can result from repeated infections. While it could potentially cause some similar symptoms, it is less likely given the acute presentation and specific findings.
- E) Scalp cellulitis: This condition involves an infection of the skin and subcutaneous tissues of the scalp. While it could cause fever and irritability, the specific findings related to the ear and tympanic membrane make it a less likely diagnosis in this case.