Nictitating membrane in trisomy 18 syndrome

Area of Science:

• Genetics
• Developmental Biology
• Ophthalmology

Background:

• Trisomy 18 (Edwards) syndrome is a severe genetic disorder associated with multiple congenital anomalies.
• The syndrome typically presents with characteristic dysmorphic features and developmental delays.

Observation:

• A male infant born after a prolonged gestation presented with classic, somatic, and dermatoglyphic features of trisomy 18.
• A bilateral nictitating membrane was observed, a rare finding in humans, which moved horizontally and cephalad for closure.
• This membrane occasionally obscured the conjunctiva and cornea, mimicking corneal clouding.

Findings:

• Cytogenetic analysis confirmed the diagnosis of trisomy 18 (Edwards) syndrome.
• The presence and unique horizontal, cephalad-moving nictitating membrane represent an unusual ocular finding in this syndrome.
• The nictitating membrane's ability to cover the cornea completely highlights a potential diagnostic challenge for corneal opacity.

Implications:

• This case expands the phenotypic spectrum of trisomy 18, particularly regarding ocular manifestations.
• Understanding the nictitating membrane's function in this context may offer insights into comparative anatomy and developmental anomalies.
• Further research into such rare presentations can improve diagnostic accuracy and understanding of genetic syndromes.