DermNet

Jessner lymphocytic infiltrate can look strikingly similar to tumid lupus erythematosus — both present as smooth, non-scaly red plaques on sun-exposed skin. For years the two were considered part of the same disease spectrum, until immunostaining (Leu 8) suggested they may in fact be distinct conditions. The cause remains unknown, though rare cases have been linked to Borrelia infection and certain medications, including duloxetine and ustekinumab. Most cases resolve spontaneously without scarring, sometimes after months or years.

Read more here: https://dermnetnz.org/topics/jessner-lymphocytic-infiltrate

An 11-year-old presented with disseminated flaccid blisters involving the skin and multiple mucosal surfaces, in the context of recent hepatitis A and supplement use. Can you think of some differential diagnoses?

Full case discussion: dermnetnz.org/cases/disseminated-blisters-in-an-11-year-old

Onychogryphosis - the "ram's horn nail" occurs when the nail matrix grows unevenly, producing a thickened, opaque nail that curls upward and deviates sideways rather than growing straight. Which direction it curves depends on which side of the nail matrix is producing more keratin. It's most often seen in older adults, particularly where nail care has been neglected or footwear has caused repeated microtrauma.

Read more here: https://dermnetnz.org/topics/onychogryphosis

Male pattern hair loss isn't simply "losing hair" - it's a gradual shortening of the hair growth cycle. Dihydrotestosterone (DHT) shrinks the anagen (growth) phase from years down to just weeks or months, causing follicles to miniaturise and produce progressively finer hairs until they stop growing altogether. It affects nearly all men to some degree, with genetic susceptibility inherited from both sides of the family.

Read more here: https://dermnetnz.org/topics/male-pattern-hair-loss

Pitted keratolysis is a superficial bacterial infection of the stratum corneum, most often affecting the soles of the feet, and characterised by crater-like pits and a distinctive malodour. Although frequently asymptomatic, it can cause discomfort and significant psychosocial impact.

This carousel summarises the causative organisms, risk factors, and current treatment approaches.

Miliaria is a common but underappreciated eruption caused by obstruction of the eccrine sweat ducts and presents differently depending on the depth of blockage. Miliaria crystallina, the most superficial form, produces fragile clear vesicles with no surrounding inflammation and is frequently seen in neonates and febrile hospitalised patients.

Miliaria rubra is the classic "prickly heat" sits deeper in the epidermis, causing itchy non-follicular papulovesicles in areas of friction and heat, affecting up to 30% of adults newly exposed to tropical climates.

The rarest form, miliaria profunda, involves the dermal-epidermal junction and can impair thermoregulation significantly enough to cause heat exhaustion. Management is primarily environmental - cooling, reducing occlusion, and allowing the skin to breathe, though secondary bacterial infection and folliculitis warrant consideration in persistent or pustular cases.

Read more here: https://dermnetnz.org/topics/miliaria

Pyogenic granuloma is a rapidly growing, friable vascular papule or nodule that bleeds profusely with minimal trauma which can be often alarming patients out of proportion to its benign nature. Most commonly seen on the fingers, lips, and gums, and frequently triggered by minor injury, pregnancy, or certain medications (including retinoids and EGFR inhibitors). Despite its misleading name, it is neither an infection nor a true granuloma - histologically it is a lobular capillary haemangioma. Spontaneous resolution can be uncommon and shave excision with curettage and cautery remains the mainstay of treatment, though recurrence rates of up to 40% have been reported.

Read more here: https://dermnetnz.org/topics/pyogenic-granuloma

Sunburn is an acute inflammatory reaction to excessive ultraviolet radiation exposure. It can range from mild erythema to severe blistering, and repeated or severe episodes are associated with a significantly increased risk of skin cancer, including melanoma. This carousel outlines the underlying causes, risk factors, clinical features, and evidence-based approaches to treatment and prevention.

Swipe on our carousel to find out more.

Acquired dermal macular hyperpigmentation, also called acquired macular pigmentation of unknown aetiology, comprises three conditions: 1) Erythema dyschromicum perstans 2) Lichen planus pigmentosus and 3) Idiopathic eruptive macular hyperpigmentation.

The term acquired dermal macular hyperpigmentation is useful because the three conditions overlap. Learn more via https://dermnetnz.org/topics/acquired-dermal-macular-hyperpigmentation

Lichen planus is a chronic inflammatory condition that can affect not just the skin, but also the mouth, nails, scalp, and ge****ls. On the skin, it typically appears as shiny, flat-topped purple papules and is most commonly on the wrists, lower back, and ankles. It affects around 1% of the population worldwide, mostly adults aged 30–60. Learn more via https://dermnetnz.org/topics/lichen-planus