Idiopathic Unilateral Enlargement of the Extraocular Muscles in an Infant

Area of Science:

• Ophthalmology
• Pediatric Neurology
• Histopathology

Background:

• Extraocular muscle enlargement can indicate various orbital pathologies, including thyroid eye disease, myositis, and neoplastic infiltration.
• Differentiating causes of unilateral extraocular muscle enlargement in infants is crucial for appropriate diagnosis and management.
• Idiopathic enlargement of extraocular muscles is an exceptionally rare condition with limited documented cases.

Observation:

• A 6-month-old boy presented with a unilateral deficit in right eye motility across all gaze fields.
• Neuroimaging showed enlargement of the medial, lateral, and inferior rectus muscles, with tendon sparing.
• Extensive workup excluded thyroid eye disease, inflammatory conditions, neoplastic infiltration, and vascular anomalies.

Findings:

• Muscle biopsy revealed normal architecture, lacking inflammation, infiltration, or fibrosis.
• The clinical presentation and biopsy findings were inconsistent with typical thyroid eye disease.
• The constellation of findings suggests a rare case of idiopathic enlargement of the extraocular muscles.

Implications:

• This case highlights the diagnostic challenges posed by rare orbital conditions in infants.
• It underscores the importance of considering idiopathic enlargement of extraocular muscles in the differential diagnosis.
• Further research into the etiology and management of idiopathic enlargement of extraocular muscles is warranted.