Question

A child is born with an absent finger. What is the likely diagnosis?

• A. Amniotic band syndrome
• B. Arthrogryposis multiplex
• C. Polyhydramnios
• D. Congenital constriction ring

Hint:

Absent digits or limb amputations at birth strongly suggest amniotic band syndrome.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question describes a congenital limb deformity (missing digit). We need to identify the most common mechanical cause of such amputations in utero.
Step 2: Detailed Explanation:

Amniotic Band Syndrome (ABS): Also known as Streeter's dysplasia. It occurs when the inner membrane of the amniotic sac (amnion) ruptures without affecting the outer sac (chorion).

Mechanism: This rupture creates thin, fibrous bands of amnion that float in the amniotic fluid. These bands can wrap around fetal parts, most commonly the limbs, fingers, or toes.

Constriction and Amputation: As the fetus grows, the bands tighten, acting as a tourniquet. This leads to "congenital constriction rings." If the constriction is severe enough to cut off the blood supply, it results in the auto-amputation of the distal part (e.g., a finger or toe) before birth.

Clinical Findings: The defects are usually asymmetrical and random. They range from simple skin indentations to complete absence of digits or limbs, and sometimes facial clefts.

Why not others?
- Arthrogryposis (B): Causes multiple joint contractures and stiffness, but not amputations.
- Polyhydramnios (C): An excess of amniotic fluid, which is a sign, not a cause of limb loss.

Step 3: Final Answer:
Amniotic band syndrome is the classic cause of congenital, non-genetic digital amputations due to fibrous entrapment in utero.