A female infant is born with Turner syndrome (45,X). Which of the following mechanisms best explains the characteristic webbed neck (pterygium colli) and cystic hygroma seen in Turner syndrome?
- A Lymphatic obstruction during fetal development due to hypoplastic lymphatic channels leading to lymphedema and hygroma ✓
- B Deficiency of SHOX gene on the pseudoautosomal region causing connective tissue dysplasia
- C Haploinsufficiency of KIF1C causing failure of lymphatic valvulogenesis
- D Excess estrogen receptor expression stimulating fibroblast proliferation
Explanation
The webbed neck in Turner syndrome results from resolution of a fetal cystic hygroma — a lymphatic malformation caused by failure of the jugular lymph sacs to connect with the venous system. The lymphedema distends the posterior neck skin, and when it resolves postnatally, it leaves the characteristic redundant nuchal skin (pterygium colli). The cystic hygromas (neck cysts seen on prenatal ultrasound with nuchal translucency ≥3.5 mm) are strongly associated with monosomy X. SHOX haploinsufficiency explains the short stature. The streak gonads result from accelerated ovarian follicle atresia due to the missing second X chromosome.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.