Aplasia cutis congenita (ACC) is a rare condition present at birth, characterized by a localized absence of skin. This means a newborn is born with an area where skin has not fully formed, appearing as a defect on the body. It is estimated to occur in approximately 1 to 5 out of every 10,000 live births worldwide. While it can occur anywhere on the skin surface, it is most frequently observed on the scalp, particularly at the top of the head. Discovering such a condition in a newborn can naturally cause concern for parents, and understanding its nature is the first step in addressing it.
What is Aplasia Cutis Congenita
Aplasia cutis congenita (ACC) manifests as a distinct area of missing skin. These lesions are typically well-demarcated, meaning they have clear boundaries, and do not show signs of inflammation. The appearance can vary, ranging from a thin, transparent membrane through which underlying structures might be visible, to an open ulcerated wound. Some defects may even have a membranous covering that appears fluid-filled, sometimes called a bullous appearance. In some membranous lesions, a tuft of long, dark hair around the defect, known as a “hair collar sign,” may be present, which can suggest underlying cranial dysraphism.
The size of these lesions can also differ significantly, from just a few millimeters to more than 10 centimeters in diameter. Their depth can range from superficial involvement of only the top layer of skin (epidermis) to full-thickness defects that extend through the dermis and subcutaneous tissue, occasionally even involving the underlying bone. Approximately 15% to 30% of scalp ACC cases are associated with underlying bony defects, making a thorough assessment important.
While the scalp vertex is the most common location, accounting for 70% to 90% of cases, ACC can appear on other parts of the body. These less common sites include the face, trunk, and limbs.
How Aplasia Cutis Congenita Develops
The exact reasons behind the development of aplasia cutis congenita are not fully understood, but it is believed to result from impaired prenatal skin development. In the majority of cases, particularly Type I which primarily affects the scalp, the cause is considered sporadic and unknown. This means it often occurs without a clear identifiable reason or family history. Theories regarding its development include intrauterine trauma or disruptions to the vascular supply during fetal development.
Genetic factors are implicated in some rare forms of aplasia cutis congenita, where it may be part of a broader syndrome. Conditions like Adams-Oliver syndrome or certain types of epidermolysis bullosa can include ACC as a feature, indicating underlying genetic mutations. Additionally, certain maternal exposures during pregnancy, such as specific medications like methimazole, valproic acid, or benzodiazepines, have been associated with ACC in some instances, though these are not common causes.
Identifying and Treating Aplasia Cutis Congenita
Aplasia cutis congenita is typically identified immediately at birth through a visual examination of the newborn’s skin. The distinct appearance of a missing skin area usually makes diagnosis straightforward. Healthcare providers will conduct a thorough examination to assess the lesion’s depth and size, and to check for any other associated anomalies. It is also important to differentiate ACC from birth trauma caused by instruments like scalp electrodes or forceps.
For larger or deeper lesions, especially those suspected of involving underlying bone or structures, imaging studies may be utilized. An ultrasound or magnetic resonance imaging (MRI) can help determine the defect’s extent and rule out connections to the central nervous system.
Treatment approaches depend on the lesion’s size and depth. Small, superficial defects are often managed conservatively, focusing on gentle wound care to promote natural healing and prevent infection. This typically involves daily cleaning and applying protective dressings. Topical antibiotics might be used if infection is a concern, and steps are taken to prevent bleeding, particularly with deeper lesions.
Larger or full-thickness defects, especially those exposing bone or at high risk of complications, may require surgical intervention. Surgical options include skin grafting, using healthy skin from another body part to cover the defect, or local flap repair, moving adjacent skin to close the wound. The timing of such procedures is carefully considered by medical professionals for optimal results.
Recovery and Expectations
The recovery process for aplasia cutis congenita largely depends on the initial size and depth of the lesion. Most small, superficial defects typically heal well over several months with conservative care, forming a scar. This healed area will usually appear as a hairless patch.
For larger defects or those requiring surgical repair, a more noticeable scar will remain. While hair may grow around the periphery of the scar, it generally does not regrow within the repaired area itself. Consistent follow-up with healthcare providers is important to monitor the healing process.
In cases of isolated aplasia cutis congenita, the overall health and development of the infant are typically unaffected. The long-term consideration is the cosmetic appearance of the scar.