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Newborn male with alopecia
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Finishing rounds in the nursery, you begin to examine the last newborn. The patient is an infant boy born via normal spontaneous vaginal delivery at 39 weeks gestation to a G2P1001 healthy mother. There were no complications with the pregnancy or delivery. While evaluating the scalp, you notice an area of alopecia on the vertex of the scalp. You review the records again and confirm that instrumentation was not required to assist in the delivery. However, he did have a fetal scalp monitor. Upon further examination, you see a discrete 2-cm well-defined, smooth, round, skin-colored alopecic plaque. The hair shafts surrounding the plaque are darker and thicker than his other hairs and form a distinct ring. The neurological examination and remainder of the physical examination are normal.
What is your diagnosis?
Diagnosis: Aplasia Cutis Congenita
Aplasia cutis congenita (ACC) is congenital absence of the skin often accompanied by loss of subcutaneous tissue, bone or dura. The pathogenesis is unclear, but ACC has been proposed as a forme fruste of a neural tube defect and may be associated with genetic abnormalities.
ACC occurs when there is a disruption in skin development. Possible etiologies include trauma, teratogens, intrauterine infections, vascular compromise and genetic factors. Clinical presentations are varied and include an ulceration or erosion, atrophic scar, blister, or round or oval defect covered by a thin translucent membrane. The latter is known as membranous ACC. Bullous defects may contain serous fluid at birth. If not present as a scar at birth, the defect tends to flatten into a scar over time and may become atrophic.
Marissa J. Perman is a second-year dermatolology resident at the University of Cincinnati.
ACC can occur anywhere on the body. However, more than 85% of defects arise on the scalp, most commonly near the vertex. The lesion is often associated with a peripheral ring of hair known as the “hair collar sign.” The hair collar sign may indicate underlying CNS abnormalities. About 25% of patients with this finding present with multiple lesions. ACC involves an underlying structure about 20% to 30% of the time. This can include subcutaneous tissue, bone, dura or leptomeninges. Stellate or angulated defects due to vascular insufficiency or intrauterine ischemic insults are often seen on the trunk and/or extremities and have a hemorrhagic or granulating base.
Certain syndromes and diseases may be associated with particular patterns of ACC. Patients with Adams-Oliver syndrome have terminal transverse limb defects, cardiac malformations, central nervous system defects, cutis marmarata telangectactica congenita and scalp ACC consisting of midline irregularly shaped defects. Other associated syndromes include Trisomy 13 (Patau syndrome), Wolf-Hirschhorn syndrome, Delleman syndrome and Johanson-Blizzard syndrome, to name a few. Patients with all types of epidermolysis bullosa can have ACC on the extremities that are characterized by large, well demarcated erosions. ACC is also associated with embryologic malformations such as encephaloceles, spinal dysraphism, sternal cleft abnormalities and omphaloceles.
Teratogens, congenital infections and intrauterine trauma can be associated with ACC. Methimazole is well documented to be associated with scalp ACC and should be avoided in pregnancy. Patients with intrauterine herpes simplex and varicella infections may develop ACC at any site. Intrauterine instrumentation for fetal reduction can also lead to ACC. Obstetric trauma from forceps or scalp electrodes is not associated with ACC.
ACC is diagnosed by clinical findings. The most commonly confused diagnosis is nevus sebaceous of Jadessohn, which also presents with a congenital patch of alopecia but usually has a pebbly, orange surface. Particular attention should be paid to potential genetic abnormalities. As ACC may be hereditary, a careful family history should be obtained. Imaging studies should be obtained when defects are large, deep or membranous, or to evaluate underlying bony, vascular or neural tissue anomalies.
The management of smaller, non-complicated healing lesions is conservative and includes keeping the area clean and applying antibiotic ointment as needed. Well-healed scars do not require further treatment. If there are cosmetic concerns, surgery and hair transplantation are possible options. Potential complications of larger defects include meningitis, sagittal sinus hemorrhage or sagittal sinus thrombosis. Early surgical intervention should be considered in these cases. It is important for clinicians to recognize ACC and its possible implications so patients can be evaluated and treated properly.
For more information:
- Bolognia, Jean L, Jorizzo, Joseph L and Rapini, Ronald P. Dermatology, 2nd edition. Philadelphia: Elsevier, 2008; pp 890-2.
- Drolet B, Prendiville J, Golden J, Enjolras O, Esterly NB. ‘Membranous aplasia cutis’ with hair collars. Congenital absence of skin or neuroectodermal defect? Arch Dermatol. 1995;131(12):1427-31.
- Frieden IJ. Aplasia cutis congenital: a clinical review and proposal for classification. J Am Acad Dermatol. 1986;14(4):646-60.