Aplasia Cutis Congenita: Causes, Diagnosis & Treatment Guide
Rare congenital skin defect: localized absence of skin, often on scalp, with variable causes and management strategies.
Aplasia cutis congenita (ACC), also known as aplasia cutis, is a rare congenital disorder characterized by the localized or widespread absence of skin layers at birth, most commonly affecting the scalp vertex. This condition involves a defect in the epidermis, dermis, and sometimes deeper tissues like subcutaneous fat or bone, presenting as erosions, ulcers, bullae, or healed scars.
What is aplasia cutis congenita?
Aplasia cutis congenita refers to the congenital absence of skin, typically presenting as a solitary or multiple lesions at birth. The most frequent site is the scalp (70-90% of cases), particularly the midline vertex, though it can occur on the face, trunk, limbs, or extremities. Lesions vary in size from millimeters to over 10 cm and may be covered by a thin, transparent membrane, exposing underlying structures like skull or dura in severe cases. ACC can be nonsyndromic (isolated) or syndromic, associated with genetic disorders, teratogens, or malformations.
Who gets aplasia cutis congenita?
ACC affects approximately 1 in 20,000 to 100,000 live births, with no strong gender predilection, though some reports suggest a slight female predominance. It manifests at birth and is sporadic in most cases (about 70-80%), but familial inheritance occurs in 15-30% via autosomal dominant (most common) or recessive patterns. Risk factors include maternal exposure to teratogens (e.g., methimazole), infections, trauma, or vascular disruptions during pregnancy. It occurs across all ethnicities.
What causes aplasia cutis congenita?
The etiology is multifactorial and not fully elucidated, involving genetic, vascular, and environmental factors. Proposed mechanisms include:
- Genetic mutations: Linked to genes like BMS1; autosomal dominant inheritance with variable expressivity.
- Vascular compromise: Placental infarcts, thrombosis, or amniotic band disruption leading to tissue necrosis.
- Teratogens: Maternal use of antithyroid drugs (methimazole, carbimazole), valproic acid, or hyperthermia.
- Infections: Intrauterine varicella, herpes, or cytomegalovirus.
- Trauma: Amniocentesis or mechanical forces.
Histopathology of fresh lesions shows absent epidermis/dermis with vascular proliferation; healed lesions exhibit dense fibrosis and absent adnexa.
What are the clinical features of aplasia cutis congenita?
Lesions appear as well-demarcated areas of missing skin, often oval or round, at birth. Common presentations include:
- Solitary scalp ulcer or erosion (classic type).
- Thin translucent membrane (membranous ACC).
- Scar-like plaque indicating prenatal healing.
- Bullae or erosions on extremities (type 2).
- Large scalp defects exposing bone/dura (high-risk).
Associated signs: hair collar sign (tuft of coarse hair around lesion), indicating neural tube defects; vascular stains; limb anomalies. Systemic involvement in syndromic forms includes gastrointestinal atresia, cardiac, renal, or CNS malformations.
How is aplasia cutis congenita classified?
Frieden classification divides ACC into 9 types based on location, pattern, and associations:
| Type | Characteristics | Associations |
|---|---|---|
| 1 | Scalp ACC without multiple anomalies (70%) | Isolated |
| 2 | Scalp with limb abnormalities | Bullae on limbs |
| 3 | Scalp with epidermal nevus/syndrome | Organoid nevi |
| 4 | Overlying embryologic malformations | Meningocele, porencephaly |
| 5 | Associated with fetus papyraceus | Twin demise |
| 6 | With epidermolysis bullosa | |
| 7 | Lower limb ectopia | Amniotic bands |
| 8 | Membranous ACC (face/scalp) | Adams-Oliver syndrome |
| 9 | Malformation syndromes (e.g., Goltz, AEC) | Focal dermal hypoplasia |
This system guides prognosis and workup; types 1 and 8 are common.
Diagnosis
Diagnosis is clinical at birth based on characteristic skin defects. Differential includes congenital erosive dermatosis, encephalocele, or herpetic infection. Confirm with:
- Imaging: Skull X-ray/ultrasound for bone defects; MRI for CNS involvement (if midline, hair collar, or >5 cm).
- Biopsy: Rarely needed, shows absent skin layers.
- Genetic testing: For syndromic suspicion or family history.
High-risk features prompting urgent evaluation: lesion >5 cm, vertex location, exposed dura, hemorrhagic bulla.
Treatment of aplasia cutis congenita
Management is tailored to lesion size, depth, and complications. Conservative for small lesions (<2 cm):
- Moist wound care: Non-adherent dressings, antibiotics if infected.
- Protect from trauma/infection.
Surgical for large/deep lesions:
- Full-thickness skin grafts, flaps, or tissue expanders.
- Cranioplasty if skull defect.
- Neurosurgical if dura exposed/sinus risk.
Monitor for healing (most heal with atrophic scar/hair loss). Multidisciplinary: dermatology, neurosurgery, genetics.
What is the outcome for aplasia cutis congenita?
Prognosis is excellent for isolated small scalp lesions (self-heal with scar). Complications (20-55% mortality in severe cases) include infection, sagittal sinus hemorrhage, meningitis, or thrombosis. Long-term: alopecia, scar contracture, or syndromic issues. Early intervention improves outcomes.
Prevention
No specific prevention; avoid teratogens in pregnancy, manage infections. Genetic counseling for familial cases.
Frequently Asked Questions
Q: Is aplasia cutis congenita hereditary?
A: Often sporadic, but 15-30% familial (autosomal dominant). Genetic testing recommended for recurrences.
Q: Can aplasia cutis congenita be fatal?
A: Yes, in extensive scalp defects exposing dura/sinus (20-55% mortality from hemorrhage/infection).
Q: Does aplasia cutis congenita always affect the scalp?
A: No, 70-90% scalp, but can involve trunk/limbs (types 2,7).
Q: How is large aplasia cutis treated in newborns?
A: Urgent surgical closure (grafts/flaps) to prevent complications like sagittal sinus bleeding.
Q: What does a hair collar sign mean in ACC?
A: Indicates underlying neural tube defect (type 4); requires MRI.
This comprehensive overview draws from peer-reviewed and institutional sources for accuracy in understanding and managing aplasia cutis congenita.
References
- Cutis Aplasia | Atrium Health Wake Forest Baptist — Wake Forest Baptist Health. 2023. https://www.wakehealth.edu/condition/c/cutis-aplasia
- Aplasia Cutis Congenita – Symptoms, Causes, Treatment — NORD (National Organization for Rare Disorders). 2024-01-15. https://rarediseases.org/rare-diseases/aplasia-cutis-congenita/
- Aplasia Cutis Congenita – StatPearls — NCBI Bookshelf, NIH. 2023-10-20. https://www.ncbi.nlm.nih.gov/books/NBK535403/
- Complex Cutis Aplasia — Children’s Hospital of Philadelphia (CHOP). 2024. https://www.chop.edu/conditions-diseases/complex-cutis-aplasia
- Nonsyndromic aplasia cutis congenita — MedlinePlus Genetics, NIH. 2023-11-01. https://medlineplus.gov/genetics/condition/nonsyndromic-aplasia-cutis-congenita/
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