Congenitally dysplastic inferior rectus muscle.

The authors report an unusual presentation of an idiopathic congenitally dysplastic inferior rectus muscle that responded well to surgical correction. Isolated unilateral enlargement of extraocular muscles is rare in children, and there is no definite logical explanation for its cause. A 20-month-old child presented with a congenitally enlarged posterior part of the right inferior rectus muscle with prominent hypotropia and enophthalmos since 10 months of age. Systemic disease work-up, ultrasound B-scan, computed tomography of the orbit and brain, and inferior rectus muscle biopsy were performed. Preoperatively, the child had severe hypotropia of the right eye with retraction of the globe. Work-up for systemic diseases was negative. Computed tomography scan showed thickening of the posterior two-thirds of the inferior rectus muscle. Muscle biopsy showed non-specific fibrotic changes. Strabismus surgery was undertaken at 2 years of age. Hypotropia was reduced significantly postoperatively. Compensatory head position was eliminated.