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Nevus psiloliparus is a rare fatty tissue nevus that is a marker for encephalocraniocutaneous lipomatosis, a neurocutaneous syndrome with ocular and central nervous system anomalies. Clinically, nevus psiloliparus is often described as a congenital alopecia and appears as an irregularly shaped, circumscribed area of alopecia on the scalp. Histopathology demonstrates a near-complete absence of mature hair follicles with preservation of arrector pili muscles and mature adipocytes within the dermis. The pathogenesis of nevus psiloliparus may be related to mosaic mutations in fibroblast growth factor receptor 1. Herein we report the histopathological features of a nevus psiloliparus in an 11-year-old girl diagnosed from transverse sections, which show "shadow" follicular units characterized by columns of loosely arranged collagen and a relative paucity of elastic fibers.

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.

The erythrodermic patient is often challenging and requires careful evaluation. Work-up should include an extensive and careful medication history, histological and laboratory testing, and if necessary, molecular studies for the evaluation of underlying malignancy. Herein, we present an erythrodermic patient with repeated biopsies demonstrating a spongiotic process who was found to have circulating atypical T-cells concerning for an underlying erythrodermic T-cell leukemia, most closely related to Sézary syndrome.

Psoriasis prevalence has long been considered to be 2-4% in the United States (US). Recently, prevalence rates of 0.5-0.6% were reported in Medicare patients and 0.128% in commercially insured children. We investigated psoriasis prevalence among commercially insured individuals younger than 65 years. The Truven Health Analytics MarketScan Commercial Claims and Encounters databases, which includes beneficiaries of employer-based commercial insurance in the US, was interrogated for continuously enrolled beneficiaries from 2011-2017. Psoriasis cases were identified using >=1 or >=2 inpatient or outpatient claims by any physician (ICD-9-CM code 696.1; ICD-10-CM codes L40.0-L40.4, L40.8, L40.9). Annual prevalence and 95% confidence intervals (CI) were calculated for each year separately. Information on gender and age range was also collected. Defining psoriasis as >=1 claim yielded a prevalence of 0.529% (95% CI 0.526-0.531) in 2011 and 0.718% (95% CI 0.714-0.721) in 2017. Women (51.7-53%) were slightly more represented than men (48.3-47%). Prevalence rose in the 18-34 years and 45-54 years age groups, reflecting a bimodal distribution of onset of psoriasis. When using >=2 claims of psoriasis as the definition, the prevalence fell to 0.220% (95% CI 0.219-0.222) to 0.329% (95% CI 0.326-0.331) during the study period. This study suggests that psoriasis is possibly up to 4-fold less prevalent than previously believed with a prevalence of 0.5-0.7% using >=1 claim of psoriasis as our criterion. When using 2 claims for psoriasis, a more clinically vigorous case definition, prevalence dropped to 0.2-0.3%. This replicates observations of previous studies and reflects the greater positive predictive value of using multiple claims for psoriasis as compared to one claim. Limitations of our study include diagnosis misclassification and the restriction to commercial insurance beneficiaries. Given the effects of psoriasis on quality of life, comorbid conditions, and health care utilization, a re-appraisal of the prevalence of psoriasis in the US is a necessary consideration.
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