Histologic Cutaneous Modifications After the Use of EMLA Cream, A Diagnostic Pitfall: Review of 13 Cases

While the eutectic mixture of lidocaine and prilocaine (EMLA cream; AstraZeneca International, Södertälje, Sweden) is the topical anesthetic most widely used before performing a skin biopsy,^1,2 EMLA-induced cutaneous histologic alterations have rarely been reported.^3-5 We herein report 13 cases where pathological diagnosis was highly complicated by EMLA application.

We reviewed 13 skin biopsy specimens obtained after EMLA application from children (mean ± SD age, 3.6 ± 4.4 years) with erythematous and squamous disease (n = 4, patients 1-4), keratinization disorder (n = 4, patients 5-8), bullous disease (n = 3, patients 9-11), and suspected storage (n = 1, patient 12) or connective tissue (n = 1, patient 13) disorders.

In addition to histopathologic findings in relation to suspected diagnoses, unexpected striking features were observed in 9 biopsy specimens (Figure 1). A diffuse pallor with swollen upper keratinocytes was seen in 7 specimens (patients 1-3, 5, 7, 9, and 10). Lower keratinocytes displayed a sharp vacuolization in 8 cases (patients 1-7 and 10). Destruction of the basal layer was observed in 8 cases (patients 1, 2, 4-7, 9, and 10). Either focal or large subepidermal cleavages were seen in 9 patients (patients 1-7, 9, and 10). In 3 cases (patients 11-13), the skin was found to be normal under standard histologic analysis.

The major ultrastructural feature was the constant vacuolization of keratinocytes occurring in the basal, spinous, granular, and/or horny layers (Figure 2). The second characteristic pattern was a marked enlargement of intercellular spaces leading to stretching or rupture of cellular interdigitations without splitting of desmosomes (n = 1, patients 6, 7, and 9-11). Finally, vacuoles were seen in 7 cases in dermal cells, fibroblasts, and/or the epithelium of sweat glands and hair follicles (patients 6-9 and 11-13). In cases devoid of pathologic features in standard histologic analysis, electron microscopy confirmed the existence of cell vacuoles in the epidermis and/or the dermis.

We describe 13 patients for whom pathologic findings were not consistent with clinical suspected diagnoses. In most cases, microscopy showed swelling and vacuolization of the upper epidermis and destruction of the basal layer resulting in cleft formation. This intriguing histologic pattern occurring in various types of cutaneous disorders after EMLA application led us to suspect the cream as the cause. Skin sensitivity to EMLA might depend on individual factors such as underlying disease, age, or application protocol. In 3 cases, there was a vacuolization of keratinocytes and dermal cells only patent on ultrathin sections.

Additional skin biopsies from areas not treated with EMLA were performed for 6 patients. Showing none of the previous alterations, these specimens allowed the adequate diagnosis of 1 case of lamellar ichthyosis, 3 cases of hereditary epidermolysis bullosa, and the exclusion of storage disease in one case and Ehlers Danlos disease in another. Our data are in accordance with the few published cases^3-5 and emphasize diagnosis difficulties caused by EMLA in a wide range of cutaneous abnormalities, especially those requiring electron microscopy.

It is important to point out that EMLA-induced histopathologic changes can favor misdiagnosis or prevent ultrastructural analysis. Therefore, dermatologists should always note the use of EMLA cream on the pathology form and, when possible, avoid its use in blistering disorders, interface dermatitis, and connective tissue or storage disorders.

Correspondence: Dr Fraitag, service d’Anatomie Pathologique, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75743 Paris CEDEX 15, France (sylvie.fraitag@nck.aphp.fr).

Financial Disclosure: None reported.