- Diagnosis is made on the basis of physical findings indicative of an in utero disruption of skin development.
- Most lesions occur on the scalp lateral to the midline, but they may also occur on the face, the trunk, or the limbs, sometimes symmetrically.
- The lesions are noninflammatory and well demarcated. The appearance of the lesions varies, depending on when they occur during intrauterine development.
- Lesions that form early in gestation may heal before delivery and appear as an atrophic, membranous, parchmentlike or fibrotic alopecic scar, whereas less mature defects may present as an ulceration of variable depth.
- With only the epidermis and the upper dermis involved, minimal alopecic scarring may result, but deeper defects may extend through the dermis, the subcutaneous tissue, and rarely the periosteum, the skull, or the dura.
- Distorted hair growth around a scalp lesion, known as the hair collar sign, is a marker for underlying defects. A bullous variant of ACC manifesting as a tense yellow vesicle on the scalp has been reported.
Copyright Mitsuhiro Sugiura, M.D.
- The histologic features of the skin vary according to the depth of the aplasia and its duration.
- At birth, ulcerated lesions may show a complete absence of skin.
- After healing, the epidermis may appear flattened with a proliferation of fibroblasts within the connective-tissue stroma and an absence of adnexal structures.
- Bullous ACC is a rare clinical subtype of ACC with distinctive histologic findings.
- Histologic evaluation of such lesions reveals a distinct pattern containing fibrovascular stromas, edematous stroma, or both.
- Identical histologic findings are found in encephaloceles and meningoceles.
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