Skin Erosions and Wound Healing in Ankyloblepharon–Ectodermal Defect–Cleft Lip and/or Palate

Ankyloblepharon–ectodermal defect–cleft lip and/or palate (AEC) (Hay-Wells syndrome, Online Mendelian Inheritance in Man No. 106220) belongs to a large, heterogeneous group of ectodermal dysplasias (EDs) that affect embryonic development of ectodermal tissues. The EDs most commonly present with defects in the hair, nails, teeth, sweat glands, and skin. The number and definition of distinct ED syndromes are ambiguous because of overlapping phenotypes and genotypes, and estimates of their overall incidence vary widely; estimates of 1:100 000 births in the United States and 7:10 000 internationally have been reported.¹

The National Foundation for Ectodermal Dysplasias convened a Skin Erosion and Wound Healing in AEC workshop conference on September 18 and 19, 2003, at the Department of Dermatology, St Louis University, St Louis, Mo. Findings from that conference are summarized in this article.

Recent discoveries have linked AEC and a closely related ED, ectrodactyly–ectodermal dysplasia–clefting syndrome (EEC), to mutations in the P63 gene, a homologue of P53, that result in the overexpression of P63 isoforms.² In AEC, these P63 mutations can give rise to a varied range of phenotypes affecting not just the skin but limb formation, teeth, and hearing. In this issue of the ARCHIVES, Payne et al³ further delineate that the P63 gene controls processes such as morphogenesis, stem cell differentiation, and wound healing.⁴ Case 1 in the report by Payne et al was one of the 12 examined by the workshop participants (Table).

The distinctive feature of AEC, ankyloblepharon filiforme adenatum, is seen in about 70% of cases. Congenital erythroderma is reported in 90% of cases. Extensive scalp erosions have been reported in 70% of patients. This problem is often present at birth and is a major cause of morbidity in affected infants and children. Heat intolerance and hypohidrosis have been reported in up to 50% of cases, but objective evidence to support eccrine dysfunction is lacking. Certain dermatologic features seem to be universal: sparse, coarse, brittle hair and characteristic nail dystrophy with small, thick, hyperconvex nails or anonychia. The palms and soles are sites of predilection classically referred to as keratoderma, but hyperkeratosis with erosion may be a more accurate description. Conjunctivitis and obstruction of lacrimal ducts and ear canals are also common. Cleft palate, with or without cleft lip, is seen in 80% of AEC cases. Other clinical features include supernumerary nipples, hypodontia, hypospadias, and malformations of the inner ear, which can lead to recurrent otitis and secondary conductive hearing loss.

Many infants with AEC are initially thought to have epidermolysis bullosa (EB). The AEC syndrome should be included in the differential diagnosis of both “collodion baby” and EB. Recognition of the distinctive congenital features of AEC will minimize unnecessary invasive diagnostic evaluation for EB. These features include facial clefting, ankyloblepharon, limb abnormalities, and the severe skin erosions accentuated on the scalp, without blisters. The skin of newborns with AEC can appear shiny, as a “collodion-membrane” phenotype. The skin erosions can mimic the denuded blisters of EB. On close inspection, it is clear that there is involvement only of the most superficial layers of the epidermis, and the erosions are much more superficial.

The following are typical clinical features of AEC:

The earliest reported biopsy findings described a 6-year-old boy with abnormal teeth, hair, nails, and sweating, with an epidermis that was “devoid of sweat glands.”⁵ All of the early references with absence of follicles and rudimentary coils, along with poorly developed sweat glands, referred to the most common form of ED: X-linked recessive hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome).^{6 - 7}

In 1968, the related unique condition “anhidrotic ectodermal dysplasia: autosomal dominant inheritance with palate and lip anomalies,” now known as Rapp-Hodgkin syndrome, was reported as featuring either absent or abnormal hair follicles, sweat gland coils, and gland tubules.⁸ In 1976, Hay and Wells⁹ described AEC syndrome, indicating that there were abnormalities of hair, nails, and “an almost complete absence of epidermal appendages,” and a later review described AEC tissues as having normal-appearing eccrine structures.¹⁰ Thus, light microscopic examination of skin was noncontributory in establishing definitively the diagnosis of AEC. No consistent histologic features were identified. Nonetheless, skin biopsy may be helpful to exclude other diagnoses, including EB.

The discovery that p63 was necessary for limb and facial development in mice² led to the molecular definition of AEC syndrome. Subsequent human molecular reports² identified P63 missense mutations affecting the carboxyl-terminal SAM (sterile α motif) domain of P63 that appear to lead to overexpression as the cause of AEC syndrome. Mutations in the P63 gene are the common thread that ties together a group of complex ED-related syndromes with overlapping phenotypes that include AEC, EEC, and Rapp-Hodgkin syndrome. But how can a mutation in a single gene result in so many different syndromes? The answer is in the precise location of the mutation, usually a single-pair amino acid substitution. The position of the mutation in the P63 gene specifies how it alters the transcriptional regulation activity and other properties of the resulting mutant P63 protein. The pattern of P63 mutations seems to be syndrome specific.¹¹

In AEC, most of the mutations clustered in regions that affect the carboxyl-terminal SAM domain, a regulator of protein-protein interactions. In both AEC and EEC, the mutations were usually “missense,” that is, the error gives rise to a single amino acid substitution that alters the normal protein function. A small number of patients have frameshift mutations, where the error causes the translation machinery to skip over a section of the gene. Intriguingly, these patients have clinical signs that strongly overlap one another, which hampers their classification as EEC or AEC syndrome.

In humans, the P63 gene spans 250 kilobases of the genome, divided into 16 exons with 2 transcription sites that can assemble 6 different isoform proteins. Although P63 is predominantly expressed in skin, the P63 promoters for the TA and δN isoforms are not sufficient to drive skin-specific expression. A genomic approach to systematically compare the P63 genomic region in mouse and humans to find highly conserved sequences (long stretches of DNA common to both) identified 40 such sequences. One of the 40 sequences elicited a strong enhancer activity in primary keratinocytes from human and mouse origin, which was inactive in other cell types. Identifying the regulatory region for P63 may lead to the identification of novel disease-associated mutations.

These recommendations are based on limited, collective experience, rather than evidence-based data. Treatment failure may still occur. Although case reports suggest that the eroded skin of newborns with AEC often normalizes within the first weeks of life, several infants described at the conference had chronic wounds complicated by life-threatening infections that healed with significant atrophic scarring.

The challenge of caring for neonates with extensive erosions includes minimizing the very high risks of percutaneous infection and toxicity. Daily bathing with gentle cotton swab debridement may be performed, as tolerated, with plain water, dilute bleach, or chlorhexidine. Pretreatment analgesia may be required. Safe and readily available wound care materials include plain petroleum jelly and petrolatum-impregnated gauze, which should be dispensed from single-use containers. Infants with severe erosions may benefit from isolette care with additionally supplied water vapor to maintain high ambient humidity. These severely affected infants will require long-term hospitalization and careful monitoring for secondary infections with a variety of organisms, including gram-positive bacteria, gram-negative bacteria, and yeast. Extended home nursing care may be required after discharge.

Extensive wound debridement and traditional skin grafting or artificial skin replacements were not successful for the infants in this series. Punch or pinch grafting was suggested as a possible alternative; no experience with these techniques in AEC exists. Irritants and potential causes of inflammation should be avoided. A very dilute Dakin solution (0.025% hypochlorite solution) was suggested between dressing changes.

For older children, major issues include pain control and the time required to care for wounds, skin, andpruritus. The risks of secondary infection are lower than for infants. A high level of vigilance for secondary infection must be balanced with restrained use of empirical antimicrobial therapy. Maintaining a healthy skin barrier is the safest way to avoid cutaneous infection. Positive skin culture results, accompanied by diagnostic signs of increasing pain, redness, swelling, and constitutional symptoms, are best treated as specifically as possible. It was suggested at the Skin Erosion and Wound Healing in AEC workshop conference that a risk-benefit assessment may support a trial of doxycycline in children younger than 8 years with unremitting scalp erosions, despite the risk of dental staining.

In assessing new therapeutic strategies for EDs, an argument can be made for the potential of epidermal stem cells in tissue repair, replacement, and regeneration. Somatic epidermal stem cells have the ability of self-renewal through division, creating 1 identical daughter stem cell and 1 transit-amplifying daughter cell that continues dividing to create populations of differentiated cells. Epidermal stem cells and their transit-amplifying sister cells are found only in the basal cell population. The stem cells make up less than 1% of the basal cell population but show their distinctive identity when separated by flow cytometry and cloned. In organotypic culture, epidermal stem cells can reform and maintain an epidermis for long periods while they continue to express their distinctive gene patterns. To test their potential in wound healing, a mouse model was used: a full-thickness wound was punched through the skin, a scab was allowed to form, and then dyed stem cells were injected just beneath the wound. On biopsy 14 days later, the wounds injected with stem cells had healed faster than the controls. Many of the stem cells were found incorporated into several tissues, suggesting that epidermal stem cells might also work as vectors for gene therapy.

Epidermolysis bullosa may provide a paradigm for the treatment of genetic skin disorders that is applicable to AEC and the ectodermal dysplasias. Recent successes in epithelial and fibroblast-mediated ex vivo gene therapy in animal model systems have raised the possibility of long-term correction of EB, an inherited disorder of the cutaneous matrix. Gene therapy for AEC will prove more challenging because the effects of in utero expression on development may not be amenable to postnatal treatment. Although replacement of wild-type genes in recessive cases of EB is relatively straightforward, a different approach would be needed for AEC. Approaches at gene therapy for dominant cases of EB are currently being explored and may eventually be applicable to AEC. Recent work on laminins in cutaneous extracellular matrix involves keratinocyte migration and illustrates how much is possible with a physiologically relevant animal model. Animal models for syndactyly and knockout mice for laminins could provide useful models for skin or scalp integrity research.

The skin erosions associated with AEC could be viewed as ulcers whose defects in reepithelialization might be exacerbated by excess angiogenesis. In venous stasis or aphthous ulcers, the loss of barrier function results in uncontrolled angiogenesis that continues as colonizing bacteria activate toll receptors, epidermis along the edges of the ulcer produce vascular endothelial growth factor, and excess matrix metalloproteinases chew up basement membrane proteins and epithelial growth factors. The success of doxycycline in the treatment of the scalp erosions in AEC may be owing to inhibition of angiogenesis.

The rarity of tissue samples from individuals affected by AEC is a deterrent to basic science efforts. Access to this potentially valuable resource must be managed judiciously to conserve the material while maximizing its scientific impact. Future AEC research efforts would be facilitated by a registry for biological materials (eg, blood, tissue culture, and whole skin), collected by a standardized protocol (available in an online eTable).

Correspondence: Dr Siegfried, Kids Dermatology, 621 S New Ballas Rd, St Louis, MO 63141 (siegfried@kidsderm.com).

Author Contributions:Study concept and design: Siegfried and Fete. Acquisition of data: Siegfried, Bree, Fete, and Sybert. Analysis and interpretation of data: Bree and Sybert. Drafting of the manuscript: Siegfried and Fete. Critical revision of the manuscript for important intellectual content: Siegfried, Bree, Fete, and Sybert. Obtained funding: Fete. Administrative, technical, and material support: Bree and Fete. Study supervision: Siegfried.

Financial Disclosure: None.

Funding/Support: The Skin Erosion and Wound Healing in AEC workshop was funded by private donations to the National Foundation for Ectodermal Dysplasias, Masroutah, Ill, from the Geismar family; St Louis University (SLU), St Louis, Mo; Scott Fosko, MD, and the Department of Dermatology at SLU; SLUCare; Cardinal Glennon Children’s Hospital, St Louis; Mölnlycke Health Care, Newtown, Pa; Connetics Corp, Palo Alto, Calif; Ferndale Laboratories Inc, Ferndale, Mich; and Novartis, Basel, Switzerland.

Additional Resources: The online-only eTable is available.

Acknowledgment: We thank the families, especially the children, who participated in the conference, as well as the following participants who donated their time, expertise, and enthusiasm to make this conference a success: Elaine Siegfried, MD, principal investigator; Virginia Sybert, MD, co–principal investigator; Jack Arbiser, MD; Jackie Bickenbach, MD; Hans van Bokhoven, MD; Mark Hurt, MD; Hynda K. Kleinman, MD; Leonard Kristal, MD; Cindy Loomis, MD; Caterina Missero, PhD; Peter Marinkovich, MD; Seth Orlow, MD; and Glenn Russo, MD. The following residents participated from St Louis University: Sarah Jensen, MD; Mary Noel George, MD; Tina Suneja, MD; Chris Kling, MD; Alanna Bree, MD; and Erin Rosewald, MD. Marc Glashofer, MD, was a resident from Tulane Hospital, New Orleans, La. We also want to thank the team from The Hospital for Sick Children in Toronto, Ontario, for their contribution to this workshop. Gail J. Neely, MD, from Washington University School of Medicine, St Louis, and Morris E. Hartstein, MD, and John A. Stith, MD, both from SLU, also participated in this workshop. John Fleischman, science writer, recorded the meeting.