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Failure of Nasolacrimal Duct Closure 1

Question

Vignette: A 6-month-old male infant is brought to the pediatrician by his mother for a routine checkup. The mother reports that everything seems normal except for a persistent clear, watery nasal discharge. On examination, the infant has a clear discharge from the nose, which increases during crying. A dye test reveals a connection from the nasal cavity to the lacrimal sac. Which of the following embryologic structures failed to close, resulting in the infant's presentation?

Choices

A. Nasolacrimal duct

B. Stensen's duct

C. Maxillary sinus

D. Eustachian tube

E. Thyroglossal duct

Answer

A. Nasolacrimal duct

Explanation

The infant's presentation is indicative of a persistent nasolacrimal duct (NLD), a condition known as congenital dacryocystocele. This occurs when the nasolacrimal duct, which normally drains tears from the eyes to the nasal cavity, fails to close properly during embryologic development. This results in a backflow of tears and mucus from the nose into the eyes, leading to a persistent, clear, watery nasal discharge that increases during crying. The nasolacrimal duct is derived from the surface ectoderm as a cord of cells that canalize by week 6 of gestation to form a patent duct. Failure of canalization can lead to dacryostenosis (blocked tear duct), presenting as excessive tearing (epiphora) or discharge in a newborn.