MEMBRANOUS APLASIA CUTIS WITH HAIR COLLARS - CONGENITAL ABSENCE OF SKIN OR NEUROECTODERMAL DEFECT

Background: The skin and the nervous system are both derived from ecto derm. Separation of neural ectoderm from epithelial ectoderm occurs co ncurrently with the closure of the neural tube. This chronologic assoc iation may explain the cutaneous abnormalities often found overlying n eural tube defects. A ring of dark long hair encircling a congenital s calp lesion (the hair collar sign) is one such marker and is often ass ociated with encephaloceles, meningoceles, and heterotopic brain tissu e. Observations: Wt describe six children with aplasia cutis who displ ayed the hair collar sign. Aplasia cutis is a relatively heterogeneous disorder; however, these lesions had a unique and strikingly similar appearance. This subtype of aplasia cutis, which we have termed membra nous aplasia cutis, shares several clinical and histologic features wi th cranial neural tube defects. Conclusions: We propose that membranou s aplasia cutis is a form fruste of a neural tube defect and may be de rived from a similar embryological defect. Recent advances in the unde rstanding of cranial neural tube closure may provide support for this hypothesis.