DermNet

The authoritative resource about dermatology and the skin: dermnetnz.org The world's most popular skin website - written and edited by Dermatologists worldwide.

02/09/2026

A digital myxoid pseudocyst isn't a true cyst as it has no capsule lining it, hence the name. It typically appears near the base of a fingernail, often pressing a visible groove into the nail plate. One key driver: many arise from the joint lining itself, as a form of ganglion linked to underlying osteoarthritis of the distal finger joint which helps explain why they're so notoriously prone to recurrence, whatever treatment is used.

Read more here: https://dermnetnz.org/topics/digital-myxoid-pseudocyst

30/08/2026

Erythema annulare centrifugum is best known for one distinctive clue: a delicate "trailing scale" just behind its slowly advancing, ring-shaped border. But the real diagnostic value lies in what's driving it - in up to 72% of cases, EAC is a reactive marker for an underlying trigger, most often a fungal infection like tinea pedis, but sometimes malignancy, medications, pregnancy, or endocrine disease. This is why identifying and treating the underlying cause, rather than just the rash, is central to management.

Read more here: https://dermnetnz.org/topics/erythema-annulare-centrifugum

26/08/2026

A 40-year-old man presented with three recurrent episodes of target-like lesions affecting the palms and soles over three months. What are your differentials for this?

23/08/2026

Knuckle pads are frequently assumed to be a callus from a repetitive habit - and sometimes they are, linked to occupational or sporting friction, or even finger sucking or biting. But true knuckle pads belong to the same family as Dupuytren contracture and Ledderhose syndrome: fibromatosis. They typically appear after age 30, can run in families, and occasionally form part of a genetic syndrome and most notably alongside keratin gene mutations in epidermolytic palmoplantar keratoderma. On ultrasound, they're distinguishable from joint synovitis, which can otherwise mimic their appearance.

Read more here: https://dermnetnz.org/topics/knuckle-pads

19/08/2026

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

17/08/2026

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

12/08/2026

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

09/08/2026

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

05/08/2026

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.

02/08/2026

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

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