DermNet

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28/12/2025

Cryotherapy using liquid nitrogen involves the use of a cryospray, cryoprobe, or a cotton-tipped applicator. The dose, freeze-time, and delivery method depend on the location, depth, size, and tissue type of the lesion. It is important to provide patients with postoperative wound care instructions and complications to be aware of.

Usually, no special attention is needed during the healing phase. The treated area may be gently washed once or twice daily with soap and water and should be kept clean. A dressing is optional but is advisable if the affected area is subject to trauma or clothes rub on it.

Read more about the procedure and treatment here: https://dermnetnz.org/topics/cryotherapy

24/12/2025

Pilomatricoma is an uncommon, harmless, hair follicle tumour derived from hair matrix cells. Cases have been reported of multiple pilomatricomas in association with the rare neurological condition myotonic dystrophy. Pilomatricomas are usually surgically excised. They do not disappear by themselves, and if incompletely removed, they may recur.

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

21/12/2025

A 25-year old female presented with rapid swelling, mottling and pain on both palms when exposed to water for a brief time (3-5 minutes). The symptoms resolve within 30 minutes after the hands are dried. What could this condition be? Read the full clinical case here: https://dermnetnz.org/cases/swollen-painful-palms-following-water-exposure

17/12/2025

Atypical fibroxanthoma (AFX) is a dermal spindle-cell tumour that typically occurs on the head and neck of sun damaged older people. Atypical fibroxanthoma is treated by complete surgical excision. Atypical fibroxanthoma rarely recurs after complete excision with clear margins. Read more here: https://dermnetnz.org/topics/atypical-fibroxanthoma

14/12/2025

Lichen nitidus is an uncommon inflammatory skin condition that usually presents with tiny skin-coloured bumps in children. The cause of lichen nitidus is unknown. Typically lichen nitidus presents as a localised bumpy skin eruption involving the flexor aspects of the forearms, backs of hands, the p***s, chest, abdomen and buttocks, however any site can be involved including the face.

Although the clinical presentation will suggest the diagnosis, lichen nitidus usually requires a skin biopsy to be confirmed. The histology of lichen nitidus is very typical and described as the ‘claw and ball’ appearance. Usually no treatment is required, as lichen nitidus does not usually cause any symptoms and resolves within 12 months in two-thirds of cases.

Read about the condition here: https://dermnetnz.org/topics/lichen-nitidus

07/12/2025

Pyogenic granuloma is an acquired benign proliferation of capillary blood vessels of the skin and oral cavity. The name is a misnomer as it is a form of lobular capillary haemangioma, not due to infection. Pyogenic granuloma has many synonyms including granuloma gravidarum or pregnancy tumour when occurring in pregnancy.

Read about about the condition here: https://dermnetnz.org/topics/pyogenic-granuloma

03/12/2025

Morphoea en coup de sabre mostly occurs in children (67%), with a slight predominance in girls (about 2:1). It usually first appears in the first two decades of life. The average age of onset was 13.6 years of age in a series of 41 patients reported from the Mayo Clinic over a 20 year period, compared to 32 patients in Wisconsin presenting at 6.9 years of age (range 1-15 years).

The clinical features of morphoea en coup de sabre evolve over months to years. En coup de sabre begins with a slightly hyperpigmented or hypopigmented streak on the forehead. Other sites may also be involved including the nose, cheek, lip, and neck. Although morphoea en coup de sabre is usually unilateral, changes can affect both sides of the face.

Read about the condition here: https://dermnetnz.org/topics/morphoea-en-coup-de-sabre

29/10/2025

Have you encountered patients with this condition? Read the case here: https://dermnetnz.org/cases/swollen-painful-palms-following-water-exposure

22/10/2025

Mastocytoma is the name given to a form of cutaneous mastocytosis in which there is a dermal accumulation of mast cells forming one to thee solitary lesions.

Pictured is positive Darier sign where the mastocytoma becomes active and inflamed following rubbing.

Read here: https://dermnetnz.org/topics/mastocytoma

19/10/2025

What is the most common virus associated with hand, foot, and mouth disease? Learn more about the condition on our DermNet page here: https://dermnetnz.org/topics/hand-foot-and-mouth-disease

15/10/2025

Gottron papules are purple papules and plaques over the tops of the small joints of the hands found in dermatomyositis. Read more about other clinical signs and information about the condition here: https://dermnetnz.org/topics/adult-onset-dermatomyositis

12/10/2025

Transient acantholytic dermatosis most often affects Caucasian men over 50 years of age with sundamaged skin (mean age at diagnosis 61 years). It is less common in skin of colour, women, and younger adults.

Risk factors include sun-exposure, sweating, fever, malignancy, and being hospitalised or bedridden. A Grover-like rash has been reported during the febrile phase of COVID-19.

Transient acantholytic dermatosis is increasingly reported with the use of BRAF-inhibitors such as vemurafenib and dabrafenib monotherapy, and cytotoxic chemotherapy drugs.

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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.