amniotic band syndrome

Amniotic band syndrome (ABS) comprises of a wide spectrum of abnormalities, all of which result from entrapment of various fetal body parts in a disrupted amnion. Due to the randomness of entrapment, each affected individual has the potential to form a unique deficit.

Epidemiology

The phenomenon is estimated to occur in ~1:1200-1300 live births .

Pathology

The exact pathogenesis is not well known, although several etiologies have been proposed.

Exogenous theory

Proposed by Torpin in 1965 , it is still the most widely accepted theory.
A disruption in the amnion allows the embryo or fetus to enter the chorionic cavity, where body parts become entangled in fibrous mesodermic strands emanating from the chorionic side of the amnion. If occurring early in gestation, this can potentially cause multiple malformations.

Endogenous theory

Proposes that a vascular insult during early embryogenesis is responsible for amniotic band syndrome .

Associations

The vast majority of cases have a sporadic occurrence . In rare situations, it may  be associated with:

• Ehlers-Danlos syndrome
• epidermolysis bullosa

Radiographic features

There is a massive spectrum of abnormalities, depending on which part becomes entrapped and at what stage of gestation. Features are often asymmetrical. Observable features according to location include:

Head/face entrapment

• acrania
• anencephaly
• facial clefts
• nasal deformities
• asymmetric microphthalmos

Truncal entrapment

• abdominal wall defects
• rib clefting
• congenital scoliosis
• ambiguous genitalia
• imperforate anus

Extremity entrapment

Limb defects tend to be the commonest :

• variable levels of limb amputation
• variable levels of limb constriction, with possible distal atrophy
• lymphedema distal to the level of the band constriction
• pseudosyndactyly
• clubfoot
• phocomelia

In addition to these defects, actual background amniotic bands may also be detected on antenatal ultrasound.

Treatment and prognosis

The prognosis is extremely variable, depending on the part that becomes entrapped. This can range from normal life expectancy at one extreme in the case of a minor distal limb entrapment to in-utero demise in the case of anencephaly from head entrapment. There is no recognized risk of recurrence for future pregnancies.

Differential diagnosis

The differential is extremely variable, depending on the type of deficit.

See also

• limb body wall complex

Siehe auch:

• limb body wall complex
• Chorion
• amnion
• Amnionblatt

und weiter:

• sandal gap deformity
• chorioamniotic separation
• obstetric curriculum
• cyllosoma
• Syndaktylie
• Lippen-Kiefer-Gaumen-Spalte
• Akranie
• Ektrodaktylie
• Anenzephalie
• Placenta extrachorialis
• kongenitale Kniegelenksluxation
• Acheirie
• Placenta circumvallata
• intrauterine Adhäsionen
• chorioamniotic membrane separation (CMS)
• Zephalozele
• kongenitale Bauchwanddefekte
• Radialstrahldefekte