Aplasia Cutis Congenita: Symptoms, Types, Causes and Treatment

Aplasia Cutis Congenita (ACC) is a rare but fascinating congenital disorder characterized by the absence of skin at birth. While it may sound alarming, ACC encompasses a spectrum of severity, from small, isolated patches that heal quickly to extensive, life-threatening defects involving deeper tissues. Understanding ACC’s symptoms, types, causes, and treatments helps families and clinicians navigate this challenging diagnosis with greater confidence and clarity.

Symptoms of Aplasia Cutis Congenita

Aplasia Cutis Congenita presents primarily as areas of missing skin, but the symptoms can vary widely depending on the size, location, and severity of the lesion. Some infants may have only a small, well-demarcated patch on the scalp, while others might have larger or multiple lesions, sometimes associated with underlying defects or other congenital anomalies. Recognizing the key symptoms is vital for timely diagnosis and management.

Manifestation	Description	Severity	Source(s)
Skin Defect	Localized or widespread absence	Mild to Severe	2 5 10
Scalp Lesion	Most common, often solitary	Usually Mild	2 5 10
Hair Collar Sign	Ring of dark, coarse hair around lesion	Suggests deeper involvement	1
Associated Anomalies	Limb, skull, or organ defects	Variable	2 3 7

Table 1: Key Symptoms

Localized or Widespread Skin Absence

The hallmark of ACC is the congenital absence of skin. Most commonly, this defect appears on the scalp, often at or near the vertex, but it can occur anywhere on the body—including the trunk, limbs, and, more rarely, the face or abdomen. The size of the lesion can range dramatically from a few millimeters to over 10 centimeters, and the depth may involve only the superficial skin layers or extend deeper, affecting the subcutaneous tissue, bone, and even the dura mater of the brain in severe cases 2 5 10.

The "Hair Collar Sign" and Other Visual Clues

A distinctive indication of potential underlying cranial or cerebrovascular involvement is the "hair collar sign"—a ring of coarse, dark hair encircling the lesion. Its presence, especially in midline or vertex scalp lesions, has been associated with a higher risk of underlying bone or vascular anomalies 1. Other visual cues may include vascular stains, nodules, or raised edges, which should prompt further investigation.

Associated Anomalies

While many cases of ACC are isolated, some present alongside other congenital defects. These can include limb reduction anomalies, organ malformations, nail dystrophy, or even more complex syndromic associations. The presence of these anomalies often signals a more complex underlying disorder and may influence both prognosis and management 2 3 7.

Severity and Course

• Small, superficial lesions: Tend to heal spontaneously, often leaving a thin, hairless scar.
• Large or deep lesions: May expose underlying structures, increasing the risk of hemorrhage, infection, or fluid loss.
• Multiple lesions or systemic involvement: Often signal a syndromic form or genetic etiology and may carry higher morbidity or mortality 3.

Types of Aplasia Cutis Congenita

ACC is not a single disease but a heterogeneous group of disorders classified based on lesion location, pattern, associated anomalies, and inheritance. Accurate identification of the type is essential for guiding workup, prognosis, and family counseling.

Type	Location/Features	Associations	Source(s)
ACC1	Scalp, solitary lesion	Usually isolated	2 3 5
ACC2	Scalp + limb anomalies	Adams-Oliver syndrome	2 10
ACC3	Scalp + epidermal/organoid nevus	Skin nevi	2
ACC4	Trunk/abdomen	Often with organ malformations	3
ACC5	Limbs after fetal death of co-twin	Placental infarcts	2 6
ACC6	With epidermolysis bullosa	Bart syndrome	2 4
ACC7-9	Associated with teratogens, infections, or other syndromes	Variable	2 7

Table 2: Classification of ACC Types

The Frieden Classification

The most widely used system for categorizing ACC is the Frieden classification, which divides ACC into nine distinct groups based on:

• Location of lesions (scalp, trunk, limbs)
• Presence of associated anomalies (limb defects, nevi, organ involvement)
• Inheritance patterns (sporadic, autosomal dominant)
• Specific syndromic associations (e.g., Adams-Oliver syndrome, Bart syndrome) 2 3 6

Common Types Explained

• Type 1 (Isolated Scalp Lesions): The classic and most frequent form, presenting as a solitary, well-circumscribed patch on the scalp, typically without other anomalies. Healing is usually rapid, and prognosis is excellent 2 3 5.
• Type 2 (Scalp and Limb Defects): Seen in Adams-Oliver syndrome, combining scalp defects with limb reduction anomalies. This type has a higher rate of genetic inheritance and may include vascular anomalies 2 10.
• Type 4 (Truncal/Abdominal Defects): Often accompanied by internal organ malformations, these cases require more comprehensive evaluation and may need surgical intervention 3.
• Type 5 (With Fetal Papyraceous): Occurs after the intrauterine death of a co-twin, resulting in skin absence primarily on the limbs. Also known as "fetus papyraceous" ACC 2 6.
• Type 6 (With Epidermolysis Bullosa): Also called Bart syndrome, characterized by skin absence, blistering, and nail abnormalities. Healing may be prolonged, but some cases resolve with conservative care 2 4.

Other Rare Types

Types 7-9 involve associations with specific teratogens, intrauterine infections (e.g., herpes, varicella), and chromosomal or other syndromic conditions. These forms are less common but may require genetic counseling and additional systemic evaluation 2 7.

Causes of Aplasia Cutis Congenita

The origins of ACC are diverse, reflecting its wide spectrum of presentations. While many cases appear sporadically, several genetic, environmental, and mechanical factors have been implicated.

Cause	Description	Association	Source(s)
Genetic	Autosomal dominant, syndromic	Family history, syndromes	2 3 7
Vascular	Placental infarcts, co-twin demise	Type V ACC	2 6
Teratogenic	Drug exposure, toxins	Antithyroid drugs, cocaine, alcohol	8 10
Intrauterine Infection	Viral (herpes, varicella)	Sporadic or syndromic	7 8 10
Mechanical	Trauma, amniotic bands	Localized defects	2 7
Unknown	No identifiable cause	Isolated cases	2 7

Table 3: Known and Suspected Causes

Genetic Factors

Some forms of ACC, especially those associated with syndromes such as Adams-Oliver or Bart syndrome, follow an autosomal dominant inheritance pattern. Family history of similar lesions or related anomalies increases suspicion for a genetic cause. Genetic counseling and molecular testing are recommended in such cases 2 3 7.

Vascular Disruption

Disrupted blood flow during fetal development—whether due to placental infarcts, in utero demise of a co-twin, or other vascular events—can lead to localized or widespread skin absence. This is particularly relevant in type V ACC, where the loss of a twin results in characteristic skin findings in the surviving fetus 2 6.

Teratogenic and Environmental Influences

Exposure to certain medications (notably antithyroid drugs), illicit substances (cocaine, heroin, alcohol), or toxins during pregnancy has been associated with ACC. These exposures may disrupt normal skin development or vascular supply to the skin 8 10.

Intrauterine Infection

Maternal infections with viruses such as varicella zoster or herpes simplex can interfere with skin development, resulting in focal or widespread defects. These cases may present with additional findings suggestive of viral infection 7 8 10.

Mechanical Factors

Physical factors like amniotic bands or trauma during gestation can cause localized skin absence. These cases are usually isolated and not associated with systemic abnormalities 2 7.

Idiopathic Cases

In many instances, no clear cause can be identified. These cases are termed "idiopathic" and most often involve isolated, superficial lesions with a good prognosis 2 7.

Treatment of Aplasia Cutis Congenita

Managing ACC requires a patient-centered and individualized approach. Treatment strategies depend on the size, depth, location, and associated risks of the skin defect, as well as the presence of underlying tissue involvement or additional anomalies. The goal is to restore skin integrity, reduce the risk of complications, and optimize cosmetic outcomes.

Approach	Indication	Method/Outcome	Source(s)
Conservative	Small, superficial lesions	Dressings, ointments, monitoring	3 4 12 13
Surgical	Large/deep defects, exposed structures	Grafts, flaps, tissue expansion	10 13 14 15
Emergency Surgery	Hemorrhage, brain/vein exposure	Split-thickness skin grafts	15
Supportive Care	All cases	Infection control, fluids, nutrition	3 13

Table 4: Treatment Strategies

Conservative Management

Small, superficial lesions with intact underlying bone and no exposure of critical structures often heal spontaneously. Treatment usually involves:

• Gentle cleansing and application of non-adherent dressings
• Topical antibiotics or emollients to promote healing and prevent infection
• Monitoring for signs of infection or delayed healing

Most lesions in this category heal within weeks, leaving a thin, hairless scar 3 4 12 13.

Surgical Intervention

For larger defects, especially those exposing bone, dura, or vascular structures (e.g., the sagittal sinus), early surgical intervention may be necessary to prevent life-threatening complications such as hemorrhage or infection 10 13 14 15. Surgical options include:

• Split-thickness skin grafts: Often used for emergency coverage in large or high-risk lesions 15.
• Local or rotational flaps: For intermediate-sized defects, allowing for closure with adjacent tissue 10 14.
• Tissue expansion: Used for delayed reconstruction to improve cosmetic outcomes 10 14.
• Cranioplasty: Rarely required, as spontaneous bone regrowth is common, but may be necessary if there is significant skull loss 14.

The timing and type of surgery depend on the defect’s characteristics and the patient’s overall condition.

Emergency Measures

Immediate surgical coverage is critical when there is exposure of major veins or the brain, as these cases carry a high risk of fatal hemorrhage. Split-thickness skin grafting has been shown to be an effective emergency intervention, with improved survival in severe cases 15.

Supportive and Multidisciplinary Care

Regardless of the primary treatment approach, all infants with ACC benefit from:

• Infection prevention and control
• Careful fluid and electrolyte management, especially in large defects
• Nutritional support to promote healing
• Genetic counseling and workup if syndromic or familial cases are suspected 3 13

Controversies and Considerations

There is ongoing debate regarding the best approach for medium-to-large scalp defects. Some experts advocate for early surgical intervention to prevent complications, while others recommend an initial conservative period, followed by delayed surgical reconstruction if needed 11 12 13 14. The decision should be tailored to each patient’s unique presentation and risk factors.

Conclusion

Aplasia Cutis Congenita is a complex, multifaceted congenital disorder that can range from mild, self-limited skin absence to severe, life-threatening anomalies. Prompt recognition, classification, and individualized treatment are key to optimizing outcomes.

Main Points Covered:

• Symptoms: Most cases involve localized absence of skin on the scalp, sometimes accompanied by the "hair collar sign" or additional anomalies.
• Types: ACC is classified into nine groups, based on lesion location, associated anomalies, and inheritance patterns. Some types are linked to specific syndromes.
• Causes: Genetic, vascular, teratogenic, infectious, mechanical, and idiopathic factors all play a role in its development.
• Treatment: Management ranges from conservative dressings for minor lesions to surgical intervention for larger or deeper defects, with supportive care being crucial in all cases.

Understanding ACC’s diverse presentations empowers healthcare providers and families to make informed decisions and support the best possible outcomes for affected children.