Embryology → pathology

Cystic hygroma: where lymph gets trapped

Tap the numbered nodes to follow the normal route, then watch the failure point create a neck lymph sac.

45,Xclassic link

posterior neck

thorax / venous angle

↘

1. Jugular lymph sacs form in the neck

Early fetal lymph sacs collect fluid from the head and neck. In cystic hygroma, this cervical lymph reservoir becomes the future problem zone.

posterior trianglemultiloculated

Lymph flowVenous angleFailed communication

Core definition

Cystic hygroma = lymphangioma from failed drainage

A congenital lymphatic malformation caused by failure of lymphatic sacs to communicate properly with the venous system. Fluid accumulates → soft, cystic, often multiloculated neck mass.

USMLE clue chain

Neck lymph sac + short female child → Turner syndrome

45,X → no Barr body
Fetal clue: increased nuchal translucency
Birth clue: cystic hygroma / webbed neck
Cardiac clue: coarctation of aorta or bicuspid aortic valve

Clinical translation

Coarctation explains leg symptoms

Narrowed aorta distal to the left subclavian artery gives upper-extremity hypertension and lower-extremity hypoperfusion → exertional leg cramping/claudication.

⚠️ Trap 1: Rib notching is not the earliest sign

Inferior rib erosion needs years of collateral intercostal artery flow. In a 5-year-old, arm-leg BP difference is more likely than visible rib notching.

⚠️ Trap 2: Barr bodies go the opposite way

Barr body = inactive extra X chromosome. Turner syndrome has only one X chromosome, so no Barr body.

⚠️ Trap 3: Not every neck mass is cystic hygroma

Thyroglossal duct cyst moves with swallowing/tongue protrusion and is midline. Cystic hygroma is classically lateral/posterior neck and lymphatic.

Tap an answer

A fetus has increased nuchal translucency. What failed embryologic event best explains cystic hygroma?

Failure of neural crest migration

Think conotruncal defects, Hirschsprung, facial anomalies.

Failure of lymph sacs to connect to venous drainage

This traps lymph in cervical lymphatic spaces.

Failure of vitelline duct obliteration

That points to Meckel diverticulum.

Failure of endocardial cushion fusion

Classically Down syndrome with AV septal defect.

Pick the mechanism. The lymph wants a venous exit ramp.

Cystic Hygroma Map