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Spring 2018, Vol. 26 No. 1

Hong Kong J. Dermatol. Venereol. (2018) 26, 47


Answers to Dermato-venereological Quiz

Answers to Dermato-venereological Quiz

FC Ip 葉方正

  1. Dermoscopy, also know as trichoscopy for hair and scalp examination.
  2. Under dermoscopic examination, the patch has a translucent appearance, with absence of follicular openings (no yellow dots). The hair roots of peripheral hairs are visible through the translucent patch (Figure 2). There are no bright yellow structures indicative of sebaceous naevus.
  3. Figure 2
  4. Membranous aplasia cutis congenita. Other differential diagnoses to be considered are sebaceous naevus, postnatal trauma by forceps or monitoring devices, Goltz syndrome and epidermolysis bullosa. The diagnosis is usually clinical, although histological examination may sometimes be required to confirm the diagnosis.
  5. Membranous aplasia cutis is the most common form of aplasia cutis congenita (ACC) and is mostly seen on the scalp. The underlying pathology is believed to be due to incomplete closure of embryonic fusion lines in the lateral scalp or face. Midline lesions could be due to incomplete closure of neural tube. A classification proposed by Frieden IJ highlighted the different categories of ACC.1 Rare clinical variants include bullous lesions at birth, which gradually flatten to the usual atrophic form after repeated episodes of rupture and blistering. When approaching an infant with ACC, clinicians should carefully delineate the morphology and location of the lesion and to look for other abnormalities, as these may be helpful in determining the aetiology, and any associated malformations and prognosis of the patient. Most membranous ACC occur as a sporadic defect and no investigations or interventions are required. Small superficial ulcerative lesions heal in several months. Small bony defects usually ossify without intervention within five to seven months. Midline defects between vertex and occiput, 'hair collar sign', nodular lesions, large lesions and presence of vascular stains have a greater risk of underlying central nervous system (CNS) abnormalities.2 Imaging studies to exclude intracranial vascular anomalies and CNS malformation should be performed in such cases.

References

1. Frieden IJ. Aplasia cutis congenita: A clinical review and proposal for classification. J Am Acad Dermatol 1986;14:646-60.

2. Patel DP, Castelo-Soccio L, Yan AC. Aplasia cutis congenita: Evaluation of signs suggesting extracutaneous involvement. Pediatr Dermatol 2018;35:e59-e61.