p-16: immunohistochemical staining to differentiate an inflamed atypical nevus

In the monitoring of patients who have had metastatic melanoma, repeat skin exams at specific intervals is a crucial screening tool to prevent recurrence. At many of these visits, suspicious melanocytic lesions are biopsied to determine if they represent a return of the patient’s melanoma. Here, we present a case of a suspicious atypical melanocytic nevus discovered during a skin exam following diagnosis of metastatic melanoma to a lymph node from an unknown primary lesion. To determine whether this lesion was melanoma, p16 immunohistochemical staining was performed of both the lymph node biopsy and the nevus, and provided a reliable means for determining the nature of the nevus. This information would be helpful to readers who care for patients with a history of melanoma who require differentiation of atypical nevi from recurrence of melanoma.https://scholarlycommons.henryford.com/merf2020caserpt/1012/thumbnail.jp

New Introductions, Spread of Existing Matrilines, and High Rates of Pyrethroid Resistance Result in Chronic Infestations of Bed Bugs (Cimex lectularius L.) in Lower-Income Housing

Infestations of the common bed bug (Cimex lectularius L.) have increased substantially in the United States in the past 10-15 years. The housing authority in Harrisonburg, Virginia, conducts heat-treatments after bed bugs are detected in a lower-income housing complex, by treating each infested unit at 60°C for 4-6 hours. However, a high frequency of recurrent infestations called into question the efficacy of this strategy. Genetic analysis using Bayesian clustering of polymorphic microsatellite loci from 123 bed bugs collected from 23 units from May 2012 to April 2013 in one building indicated that (a) 16/21 (73%) infestations were genetically similar, suggesting ineffective heat-treatments or reintroductions from within the building or from a common external source, followed by local spread of existing populations; and (b) up to 5 of the infestations represented new genotypes, indicating that 5 new populations were introduced into this building in one year, assuming they were not missed in earlier screens. There was little to no gene flow among the 8 genetic clusters identified in the building. Bed bugs in the U.S. often possess one or both point mutations in the voltage-gated sodium channel, termed knockdown resistance (kdr), from valine to leucine (V419L) and leucine to isoleucine (L925I) that confer target-site resistance against pyrethroid insecticides. We found that 48/121 (40%) bed bugs were homozygous for both kdr mutations (L419/I925), and a further 59% possessed at least one of the kdr mutations. We conclude that ineffective heat treatments, new introductions, reintroductions and local spread, and an exceptionally high frequency of pyrethroid resistance are responsible for chronic infestations in lower-income housing. Because heat treatments fail to protect from reintroductions, and pesticide use has not decreased the frequency of infestations, preventing new introductions and early detection are the most effective strategies to avoid bed bug infestations in multistory apartment buildings

Allergic Contact Dermatitis Due to Benzoyl Peroxide from an Unlikely Source

Although irritant contact dermatitis secondary to BPO is common, allergic contact dermatitis is rare. Here, we present a baker who developed allergic contact hand dermatitis to BPO in the bleached flour he used at work. Case Presentation: A 64-year-old man presented with a pruritic dermatitis involving the hands. Treatments had included triamcinolone 0.1% ointment and fluocinonide 0.05% ointment without resolution. Given the lack of improvement, the patient was referred for patch testing. Of note, the patient is a baker and has frequent contact with flour. He recalled that the onset of pruritus was associated with switching from unbleached flour to bleached flour at work.The patient underwent patch testing with the North American 80 Comprehensive Series (NAC-80). Positive reactions at the 48-hour patch read were as follows: 1+ to balsam of peru and benzoyl peroxide. The 1-week patch read resulted in a 2+ reaction to benzoyl peroxide. After avoidance of benzoyl peroxide by switching to unbleached flour and balsam of peru, the patient noted significant improvement in his pruritus and dermatitis. At his post-patch test visit, the majority of lesions had resolved with fluocinonide 0.05% ointment and avoidance of allergens. Discussion: Benzoyl peroxide dermatitis is rare and typically associated with acne medication. Providers should consider other sources of benzoyl peroxide as allergens when appropriate. Other occupational allergens, such as Balsam of Peru in bakers, should be considered as well.https://scholarlycommons.henryford.com/merf2019caserpt/1015/thumbnail.jp