Severe drug hypersensitivity reaction in a young woman treated with doxycycline.

Doxycycline is a commonly prescribed medication for the management of acne vulgaris. Severe adverse reactions to this medication are uncommon. We describe an unusual case of a 20-year-old female who experienced a life-threatening hypersensitivity reaction, including fever, lymphadenopathy, hepatitis, nephritis and severe pneumonitis with respiratory failure following oral administration of doxycycline for facial acne.

Unique histopathologic findings in a patient with adult-onset Still disease.

Adult-onset Still disease (AOSD) is an uncommon disorder characterized by fever, polyarthralgia, elevated white blood cell count, and a maculopapular rash, the histologic features of which have not been well-known. A 55-year-old Asian woman presented initially with a "burning" and severely pruritic eruption on her face, hands, and arms, thought clinically to be urticaria. Within 1 month, she began spiking high fevers, developed diffuse joint pain, and had marked elevations of ferritin, C-reactive protein, and erythrocyte sedimentation rate, characteristic of AOSD. The cutaneous eruption became more widespread, involving the trunk, scalp, and remainder of the extremities, with diffuse thickening of the skin with papular and linear hyperpigmentation and accentuation. Biopsies from several locations showed focal hyperkeratosis associated with dyskeratotic keratinocytes with a peculiar, distinctive distribution in the upper epidermis and cornified layers. In addition, increased dermal mucin was present, with minimal fibroblast proliferation and inflammation. This unusual combination of diffuse dermal mucinosis and a unique pattern of dyskeratosis can present a challenge in generating an accurate differential diagnosis, and may represent an unusual response to chronic scratching or be a distinctive histologic manifestation of AOSD.

Primary cutaneous neuroendocrine cell carcinoma (Merkel cell carcinoma) with prominent microcystic features, mimicking eccrine carcinoma.

Although primary cutaneous neuroendocrine cell carcinoma [Merkel cell carcinoma (MCC)] may show divergent features, including microcystic ('tubuloglandular'), squamous, eccrine and rhabdomyoblastic, a diffuse microcystic pattern is exceedingly rare. In this study, we present two cases of MCC with prominent microcystic features, which precluded a definitive diagnosis in the initial punch biopsy. Both patients were middle-aged men with a history of rapidly growing plaques of the back or posterior neck. Punch biopsies from both patients revealed an infiltrating neoplasm with prominent microcystic features that mimick tubuloglandular structures, lined by hyperchromatic basaloid cells, which were strongly positive for chromogranin and BerEP4, variably positive for CK7 and CK5/6 and negative for CK20, synaptophysin, S-100, epithelial membrane antigen (EMA), gross cystic disease fluid protein-15 (GCDFP-15), estrogen/progesterone receptors (ER/PR), thyroid transcription factor 1 (TTF1) and carcinoembryonic antigen (CEA). The re-excision specimens showed a multifocal intra-epidermal component in one case and typical finely stippled nuclear chromatin in both cases. Although the lack of CK20 staining is unusual, the histologic characteristics along with the remaining immunohistochemical studies favor the diagnosis of a primary cutaneous neuroendocrine cell carcinoma over the variants of eccrine carcinoma or basal cell carcinoma with neuroendocrine differentiation. Our cases illustrate that prominent microcystic features, mimicking glandular differentiation, may occur in MCC and pose a diagnostic challenge in small biopsy specimens.