The diagnosis of panniculitis is a relatively rare occurrence for many practising pathologists. The smaller subset of lymphocyte-predominant panniculitis is further complicated by the diagnostic consideration of T cell lymphoma involving the subcutaneous tissue, mimicking inflammatory causes of panniculitis. Accurate classification of the panniculitis is crucial to direct clinical management as treatment options may vary from non-medical therapy to immunosuppressive agents to aggressive chemotherapy. Many diseases show significant overlap in clinical and histological features, making the process of determining a specific diagnosis very challenging. However, with an adequate biopsy including skin and deep subcutaneous tissue, a collaborative effort between clinician and pathologist can often lead to a specific diagnosis. This review provides an algorithmic approach to the diagnosis of lymphocyte-predominant panniculitis, including entities of septal-predominant pattern panniculitis (erythema nodosum, deep necrobiosis lipoidica, morphea profunda and sclerosing panniculitis) and lobular-predominant pattern panniculitis (lupus erythematous panniculitis/lupus profundus, subcutaneous panniculitis-like T cell lymphoma, cutaneous γ-δ T cell lymphoma, Borrelia infection and cold panniculitis).

The prevalence of tattoos is increasing and as such every physician must be aware of the potential adverse events associated with tattooing. Here we present a 36-year-old man with a recent history of skin-coloured papules appearing suddenly in a 20-year-old tattoo on the right forearm. Biopsy and histologic examination confirmed a diagnosis of verrucae planae or flat warts. Tattoo-associated human papilloma virus infections develop clinical manifestations after long latency periods and are often difficult to treat. The risk of tattoo-related human papilloma virus infection should be discussed when considering acquiring a tattoo.

Dear Editor Trichotillomania (TTM), skin-picking disorder (SPD) and onychophagia are psychodermatologic conditions of primary psychiatric genesis categorized under obsessive compulsive and related disorders in the DSM-5. Due to limited efficacy of current treatments for these conditions, novel treatments, including N-acetylcysteine (NAC), are being evaluated. 1 This study comprehensively summarizes treatment outcomes of NAC for TTM, SPD and onychophagia.

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease that is characterized by the formation of comedones, papules, nodules, abscesses and sinus tracts in the axillary, inframammary, groin, and gluteal areas. Up to 3.8% of the Canadian population has HS, though due to a lack of awareness of HS, many patients are initially misdiagnosed and do not receive adequate treatment early on in the disease course. Once a diagnosis of HS is made, developing an effective management plan can be a dilemma for many providers. There is significant variability in response to any given therapy within the HS patient population and many HS patients have other medical comorbidities which must be taken into consideration. The aim of this review is to provide a practical approach for all healthcare providers to diagnose and manage HS and its associated comorbidities. A sample electronic medical record template for HS management was developed by the Canadian Hidradenitis Suppurativa Foundation Executive Board and is intended for use in clinical settings. This will help to increase collaboration between primary healthcare providers, dermatologists, and other medical specialists and ultimately improve the quality of care that HS patients receive.