Pigmented lesions of the nail unit are commonly encountered in the clinical setting. Yet, they often present a unique challenge to clinicians because of a broad differential diagnosis or unfamiliarity with clinical and histopathologic features. A wide variety of causes exist ranging from benign lesions such as subungual hemorrhage to malignant lesions such as subungual melanoma. Identifying the underlying cause is key to appropriate management and follow-up in these patients. Although emerging clinical tools such as dermoscopy can be very useful in evaluation of these lesions, histopathologic analysis remains the gold standard. In this review, we discuss and provide a summary of important clinical and histopathological concepts of pigmented lesions of the nail unit with special focus on longitudinal melanonychia, melanotic macule, melanocytic nevus, subungual melanoma, along with discussion of some nonmelanocytic lesions.

This is a report of a 15-year-old female who presented with a skin eruption and clinical features consistent with severe sepsis and septic shock. A diagnosis of acquired hemophagocytic lymphohistiocytosis (HLH) was made and confirmed by bone marrow analysis. Skin biopsy showed hemophagocytosis and CD163-positive staining of macrophages. We briefly review the clinical, histologic, and laboratory findings of hemophagocytic lymphohistiocytosis in addition to the potential role of skin biopsies in this condition.

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Psoriatic alopecia is a rare nonscarring alopecia that can present as a complication of treatment with tumor necrosis factor α inhibitors.• This finding commonly is seen in females undergoing treatment with infliximab or adalimumab, usually for Crohn disease.• Histopathologic findings can show a psoriasiformpattern, neutrophil-rich, inflammatory infiltrate involving hair follicles or a lichenoid pattern.

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