Issue: Volume 65 - Issue 7 - July 2019 ISSN 2640-5245
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Aplasia cutis congenita (ACC) is an uncommon heterogeneous group of disorders characterized by focal or widespread absence of skin from certain parts of the body. ACC occurs in 1 in 10 000 live births, with increased female predominance. Although ACC can occur on any part of the body, it most commonly affects the scalp (70% to 80%), with 30% affecting other parts of the body. The majority of cases are sporadic, isolated defects. ACC can be inherited in either autosomal dominant or autosomal recessive form and has been associated with multiple genetic conditions, including epidermolysis bullosa, congenital intestinal anomalies, trisomy 13, and Adams-Oliver syndrome.1
Most cases of ACC are noninflammatory and well-demarcated, oval or round. In 30% of cases, deeper structures are involved, including dermis and subcutaneous skull and dura tissue. Membranous ACC refers to an underlying flat, white membrane, overlaying scalp defect and can be associated with a neural cranial tube defect. Bullous ACC demonstrates a fibrovascular or edematous connective tissue similar to what is seen in an encephalocele and a meningocele, suggesting it also may be related to a neural tube defect.1-3
Many etiological factors have been suggested in ACC, including amniotic bands, areas of pressure during rapid brain growth, intrauterine infections such as varicella zoster, and cerebrovascular accidents. Teratogens such as cocaine, heroin, antithyroid hormone agents, and misoprostol have been suspected. Complications of ACC include infections, meningitis, bleeding, sagittal sinus thrombosis, and seizures; mortality rates range from 20% to 50%. Mortality increases with larger defects and those involving the underlying bone.1-3
There is no consensus or published guideline for the management of ACC. The current body of literature on ACC management and outcomes is mostly based on case reports and contains both conservative and surgical strategies. In the past, reports suggested that only small defects (<2 cm) were appropriate for conservative management (wound dressings and prophylactic systemic antibiotics); recently, reports of successful healing of large lesions with conservative management have become available, noting an average healing time of 2 to 3 months.1-4 Although no agreement has been reached on ideal surgical repair time, reports1-4 seem to suggest increased complication rates and mortality with surgical repair, partially due to more complex lesions but also due to anesthesia and surgical manipulation.
ACC treatment goals include protecting the defect, eventual epithelialization, preventing infection, avoiding wound surface drying and/or new tissue disruption leading to hemorrhage, and cerebral tissue exposure. The cephalic location of ACC lesions makes it challenging to keep the area well-covered, moist, and intact while not interfering with parental bonding and daily care. Older case studies3,4 describe topical and systemic antibiotic use. The literature is conflicting on whether topical antibiotics are as efficacious as antimicrobial agents. Some institutions use topical silver to provide antimicrobial coverage and a moist base, but recent systematic reviews and meta-analysis5,6 advise against prolonged silver use in neonates due to its known side effects, including potentially cytotoxic action against new epithelial cells and an emerging bacterial resistance. Povidone-iodine has good antimicrobial activity and has been mentioned in the literature, but the risk of hyperthyroidism in neonates is a known concern. In addition, reports of drying and separation of the scar tissue inducing a hemorrhage have deterred most clinicians from using iodine-based topical products.5
My plastic surgery colleagues favor a wet-to-moist approach that utilizes either gauze, petrolatum-based fine mesh, or a combination of petrolatum and bismuth tribromophenate (Xeroform; Covidien, Mansfield, MA) that is processed into a homogenized suspension and impregnated into fine mesh sterile gauze, all covered by dry gauze and either Kerlix bandage roll (Covidien) and/or a hat. Primary mesh dressings tend to move because keeping secondary coverage snug on the head is difficult. Use of petrolatum gauze often is combined with systemic antibiotics to prevent infection and the risk of meningitis.
In the era of antibiotic stewardship and increased resistance, neonatal practitioners are weary of prolonged, frequent systemic antibiotic administration. Although bismuth tribrimophenate unbound to Xeroform demonstrates antimicrobial activity (likely by attachment to the cell membranes), the product has been found in vitro to have a less-than-significant antimicrobial effect.7 It serves more as a barrier, minimizing moisture loss, desiccation, and trauma due to friction between the defect and the outer dressing. I have found this choice of management works, but it is a very slow, multiweek process (depending on size and depth of the defect) and requires diligent attention from parents if babies were to go home because poor coverage can lead to desiccation and secondary bleeding.
Based on a few principles, my first choices are either activated Leptospermum honey (ALH) or concentrated surfactant gel (CSG) as topical products for ACC. The goals of maintaining a moist wound base, antimicrobial coverage, gentle autolytic debridement, and promotion of new tissue growth are weighed against potential risks of hemorrhage, venous sinus thrombosis, infection, and wound breakdown.
ALH. Acidic pH and natural antimicrobial properties make ALH an excellent topical antimicrobial. It is a gentle autolytic debrider that keeps the wound clean and moist (important to keep vigilant to prevent drying out). In my experience, its progranulating effect (fibroblast migration, proliferation of collagen, angiogenesis, and immunomodulation via cytokines) hastens epithelialization.8-12 I recommend covering the honey gel with petrolatum-impregnated gauze or Telfa (Covidien) or perforated wound contact layer to minimize moisture loss and wound bed friction caused by the outer dressing or hat. Depending on the defect location (or if there are multiple defects) both products may be needed. Normally, large ACC lesions take approximately 2 months to epithelialize. In my experience, this regimen protects the wound from infection and hastens the epithelialization rate. However, one drawback of using ALH gel is its viscosity and “messy “application site at times.
CSG. Nonionic poloxamer 188-based concentrated surfactant biomaterial is built with hydrophilic and hydrophobic chains, forming sphere-like micelles that converge into a micelle gel matrix that is noncytotoxic and biocompatible.13 CSG is commonly used in adult and pediatric burns. Several mechanisms of action have been proposed, including injured cell salvage (via the insertion into the leaky cell membranes to minimize apoptosis and necrosis) and reduced inflammation (via bradykinin sequestration in the gel, decreased lipid peroxidation, and free radicals scavenge), functions deficient in preterm neonates. in vitro study13 suggests microcirculation may be enhanced and clot formation reduced, minimizing potential for hemorrhage and venous sinus thrombosis. Effective biofilm removal (via dispersion) and prevention of further biofilm formation have been demonstrated in vitro and in multicenter clinical application, leading to CSG’s utility in infected and colonized wounds. Water-based emulsion leads to effective exudate/debris solubilization and removal while protecting the underlying healthy or granulating tissue (especially due to the thickening effect of warm temperature on the gel-inverse thermodynamic reaction). CSG is easily rinsed with just water or normal saline, minimizing the difficulty of removing viscous gel found with ALH.
Case Report
A 34-weeks’ gestation male patient was transferred to my service with 3 nonmembranous ACC lesions (see Figure 1). No associated syndromic findings were appreciated. Initial management involved ALH covered by petrolatum-impregnated gauze, bandage roll, and a hat. Staff and parents had difficult time keeping the lesions moist. The defects were well-demarcated and small-to-moderate in size, but they did not respond to our initial treatment. We decided to try CSG based on its inverse thermodynamic properties and easier removal (see Figure 2). The result was excellent, with complete epithelialization within 4 weeks (see Figure 3).
Summary
It is important to physically protect ACC lesions from increased injury, decussation, and outside elements. Use of ALH or CSG decrease opportunities for outside injury and decussation. Because of the location, it often is difficult to use secondary adhesive dressings. Placing nonadherent dressings such as cotton pads or petrolatum-impregnated mesh and covering with a bandage roll and a hat has worked well for us. In the last 4 years, this approach has allowed us to avoid surgical treatment in all babies with ACC.
