DermNet

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

05/04/2026

A comedo naevus (naevus comedonicus) is a rare, benign skin condition characterised by groups of dilated hair follicle openings filled with dark keratin plugs, resembling blackheads. It is considered a type of epidermal naevus involving the pilosebaceous unit and often appears at birth or during early childhood, although later onset can occur. Lesions may appear in linear or clustered patterns on the face, trunk, or limbs and are usually harmless, though in rare cases they may be associated with systemic abnormalities as part of naevus comedonicus syndrome.

Read more here on https://dermnetnz.org/topics/comedo-naevus

01/04/2026

Methotrexate is a systemic immunosuppressive medication widely used in dermatology to treat moderate-to-severe inflammatory skin diseases such as psoriasis and eczema. By reducing immune system activity, it helps control inflammation and improve symptoms, but regular monitoring is required to ensure safe and effective treatment.

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

29/03/2026

A digital myxoid pseudocyst (also called a digital mucous cyst) is a benign, fluid-filled lesion usually found near the base of the fingernail, often over the distal finger joint. It appears as a smooth, shiny, semi-translucent bump and may cause a longitudinal groove in the nail due to pressure on the nail matrix. These cysts are commonly associated with degeneration of connective tissue or osteoarthritis of the distal finger joint. Management ranges from observation to treatments such as drainage, cryotherapy, steroid injection, or surgical removal, although recurrence can occur. Read more here: https://dermnetnz.org/topics/digital-myxoid-pseudocyst

25/03/2026

Vitiligo is a chronic autoimmune skin condition where melanocytes (the cells responsible for skin pigment) are destroyed, leading to well-defined depigmented patches on the skin. While treatment has traditionally focused on topical steroids, calcineurin inhibitors, and phototherapy, new targeted therapies are emerging. In the UK, topical ruxolitinib (a JAK inhibitor) has recently been approved as the first licensed treatment specifically for non-segmental vitiligo, helping restore pigmentation by reducing the immune attack on pigment-producing cells. Read more about vitiligo here: https://dermnetnz.org/topics/vitiligo

22/03/2026

Crusted scabies is a severe variant of scabies characterised by hyperkeratotic plaques and extremely high mite loads. It commonly occurs in immunocompromised individuals and requires prompt diagnosis, intensive treatment, and strict infection control measures. Read more about the condition here: https://dermnetnz.org/topics/crusted-scabies

18/03/2026

Lichenoid keratosis is a small, inflamed macule or thin pigmented plaque, usually solitary, with a lichenoid tissue reaction on histology. A solitary lesion is present in 90% of cases of lichenoid keratosis, with others presenting with multiple lesions. It is most commonly found on the upper trunk, followed by the distal upper extremities, and less commonly on the head and neck.

Lichenoid keratosis is harmless and resolves spontaneously.

Read more here: https://dermnetnz.org/topics/lichenoid-keratosis

15/03/2026

Miliaria (heat rash / prickly heat) is a common skin condition caused by blockage and inflammation of eccrine sweat ducts, most often seen in hot, humid or tropical climates, in hospitalised patients, and during the neonatal period.

Based on the depth of sweat duct obstruction, miliaria is classified into three types: miliaria crystallina, due to very superficial blockage in the stratum corneum; miliaria rubra, caused by obstruction in the mid-epidermis and responsible for the classic itchy red rash; and miliaria profunda, where sweat leaks into the dermis following repeated episodes of miliaria rubra.

Cooling measures and reducing sweating are key to management.

Find out more about the condition here: https://dermnetnz.org/topics/miliaria

11/03/2026

Spoon-shaped nails - what are causes for this? It could be a clue to underlying disease! Clinical case can be found here: https://dermnetnz.org/cases/what-can-cause-these-flattened-nails

08/03/2026

Exercise-induced vasculitis is a harmless form of cutaneous small-vessel vasculitis, also known as golfer’s vasculitis. It is a neutrophilic inflammatory condition affecting small to medium-sized blood vessels of the skin; when limited to capillaries, it is termed exercise-induced capillaritis.

It typically affects the lower legs and thighs after prolonged exercise, especially in warm conditions. Features include red patches, weals, and purpura on exposed skin (with sparing beneath socks), associated swelling, and symptoms such as itching, stinging, pain, or burning.

Patients are otherwise well, and lesions usually resolve within 3–4 weeks, sometimes leaving temporary brownish pigmentation.

Read more here: https://dermnetnz.org/topics/exercise-induced-vasculitis

04/03/2026

Urticarial weals vary in size from a few millimetres to several centimetres and may appear white or red, with or without a surrounding flare. Individual weals are transient, lasting minutes to hours, and often change shape. They may be round, annular, map-like, or form large confluent patches, and can occur anywhere on the body with widespread distribution.

Read more here: https://dermnetnz.org/topics/urticaria-an-overview

01/03/2026

🤔 White lesion on the cheek on a young boy - what’s your differential?
A solitary, well-defined white facial lesion can have several causes.
Swipe, zoom in, and think through the possibilities before jumping to conclusions. Diagnosis revealed within the carousel! Find the case here: https://dermnetnz.org/cases/white-lesion-on-cheek

25/02/2026

Poliosis is a clinical sign, not a diagnosis, defined by a localised patch of white hair caused by reduced or absent melanin in the hair shaft.

It has many potential causes and may result from inherited defects in melanisation or destruction of pigment cells at the hair follicle.

Poliosis most commonly affects the scalp but may also involve the eyebrows, eyelashes, beard, or body hair, and can occur with associated leukoderma or normal-appearing skin.

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

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DermNet NZ has become a world renowned resource all about the skin. The website is owned by the DermNet New Zealand Trust. It has been HON (Health-on-The-Net) certified since 1996 and is in continuous development to provide information about the skin over any desktop or mobile web browser.

Our mission is to make authoritative information about the skin accessible to anyone in the world with an internet connection.

Dr Amanda Oakley, DermNet's founder, was most recently honoured by being appointed by Her Majesty The Queen as a Companion of the New Zealand Order of Merit in recognition of her services and contribution to Dermatology. She was also awarded the Google Technology Service in the Charitable Sector's Lifetime Service Award at the New Zealand Charities Technology Awards in March 2017 and was a finalist in two categories the New Zealand Woman of Influence awards in June, 2017.