Differential Diagnosis for Unilateral Pink Eye, Crusting, and Ipsilateral Enlarged Cervical Lymph Node in a Child

Single Most Likely Diagnosis

• Viral Conjunctivitis: This is the most common cause of pink eye in children, often presenting with unilateral or bilateral involvement, crusting, and can be associated with enlarged cervical lymph nodes due to the body's immune response to the virus.

Other Likely Diagnoses

• Bacterial Conjunctivitis: Similar to viral conjunctivitis but typically presents with more purulent discharge and may require antibiotic treatment. The presence of an enlarged cervical lymph node can occur but is less common than in viral infections.
• Allergic Conjunctivitis: Seasonal or perennial allergies can cause conjunctival inflammation, but this usually presents bilaterally and is accompanied by other allergic symptoms such as rhinitis. However, in some cases, it can present unilaterally, especially if the allergen exposure is asymmetric.
• Chlamydial Conjunctivitis: More common in neonates (as a result of maternal transmission during birth) but can occur in children, often presenting with chronic conjunctivitis and ipsilateral lymphadenopathy.

Do Not Miss Diagnoses

• Gonococcal Conjunctivitis: Although rare, this condition is a medical emergency due to the risk of corneal perforation and vision loss. It presents with severe, purulent conjunctivitis and is a consideration in children who have been sexually abused or born to mothers with untreated gonorrhea.
• Herpes Simplex Virus (HSV) Keratoconjunctivitis: Can cause severe ocular disease, including keratitis and uveitis, and is associated with significant morbidity if not promptly treated.
• Tuberculous Conjunctivitis: Rare but can present with chronic conjunctivitis and lymphadenopathy. It's a consideration in areas where tuberculosis is prevalent or in immunocompromised patients.

Rare Diagnoses

• Sarcoidosis: A systemic disease that can cause uveitis, conjunctivitis, and lymphadenopathy, but it's rare in children.
• Lymphoma: Although extremely rare, lymphoma can present with conjunctival lesions and lymphadenopathy.
• Leptospirosis: A zoonotic infection that can cause conjunctivitis among other systemic symptoms, including lymphadenopathy, but it's uncommon and typically associated with specific exposures (e.g., contact with contaminated water).

Each of these diagnoses requires a thorough history, physical examination, and sometimes specific diagnostic tests (e.g., cultures, PCR for viruses, serology for chlamydia or other pathogens) to confirm the diagnosis and guide appropriate management.