Faculty Bibliography

BACKGROUND:In instances of suspected cutaneous infection, standard of care includes obtaining skin biopsies for histology and tissue culture. Few studies have compared the clinical utility of each test. OBJECTIVE:To assess the concordance of results between tissue culture and histology, and clinicopathologic features that may influence the diagnostic yield of each test. METHODS:A retrospective review of all patients who underwent skin biopsy for histology and tissue culture at New York University from 2013-2018. RESULTS:Of 179 patients, 10% had positive concordance, 21% had positive tissue culture only, and 7% had positive histology only. We calculated a kappa correlation coefficient of 0.25 between histology and tissue culture [ref 0.21-0.39=minimal agreement]. Histology exhibited higher sensitivity in detecting fungi, whereas tissue culture was more sensitive in identifying gram-negative bacteria. Antimicrobial use prior to biopsy led to significantly fewer positive cultures (37.5% versus 71%; p=0.023) in patients ultimately diagnosed with infection. LIMITATIONS/CONCLUSIONS:This study was conducted at a single institution thereby restricting its broad applicability. The lack of a validated gold standard to diagnose infection also limits interpretation of results. CONCLUSION/CONCLUSIONS:Tissue culture and histopathology often yield discordant results. Dermatologists should recognize specific test limitations, yet high clinical utility in special circumstances, when approaching cases of suspected infection.

Frontal fibrosing alopecia (FFA) represents an uncommon variant of lichen planopilaris (LPP). While the histopathology of both conditions is similar, their clinical presentations are distinct. FFA exhibits progressive recession of frontal and temporoparietal hairlines, and involvement of eyebrows, beard, and body hair with loss of follicular ostia. FFA in males represents a rare subset of cases, yet reported cases are increasing. This population necessitates further evaluation to define demographics, clinical presentation, diagnostic pearls, and effective therapies.

Direct immunofluorescence (DIF) remains a valuable tool that may be underused because of perceived challenges in the interpretation, limitations, and processing of DIF specimens. The aim of this review is to provide a practical guide for appropriately incorporating DIF in a variety of clinical diseases, such as autoimmune blistering disorders. In vasculitis, the role of DIF continues to evolve, particularly in the setting of IgA vasculitis. Although typically not indicated for the workup of connective tissue disease, DIF may be helpful in cases with negative serologies, nondiagnostic histologic findings, or scarring alopecia. Practical pearls for biopsy technique, specimen handling, and storage are also discussed.