What causes aplasia cutis congenita (ACC)?

Updated: Jun 17, 2020
  • Author: Chris G Adigun, MD, FAAD; Chief Editor: William D James, MD  more...
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Answer

No unifying theory can account for all lesions of aplasia cutis congenita (ACC). Because this condition is the phenotypic result of more than one disease process, it is likely that more than one mechanism is involved. Mechanisms include genetic factors, teratogens (eg, methimazole, carbimazole, misoprostol, valproic acid), compromised vasculature to the skin, infections, neural tube defects, and trauma. Of particular note is the association of fetus papyraceous with bilaterally symmetric aplasia cutis congenita.

The proximity of scalp aplasia cutis congenita to the scalp hair whorl, which is thought to be the point of maximum tensile force during rapid brain growth, has led to the hypothesis that tension-induced disruption of the overlying skin occurs at 10-15 weeks of gestation when hair direction, patterning, and rapid brain growth occur. This may also explain the increased incidence of aplasia cutis congenita on the vertex scalp.

Early rupture of the amniotic membranes, forming amniotic bands, has appeared to be the cause of aplasia cutis congenita in several cases.

The bullous or membranous variants of aplasia cutis congenita reveal a distinct histologic pattern identical to those in encephaloceles and meningoceles. This supports a hypothesis that these types of aplasia cutis may represent the forme fruste of a neural tube closure defect.


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