Kaposi’s sarcoma is a growth of the cells lining lymphatic vessels, caused by a virus in people with a weakened immune system. The virus is called human Herpes virus type 8 (Kaposi sarcoma herpes virus, HHV8). A common cause of the weakened immune system is HIV infection. It is named after Dr Moritz Kaposi, a Hungarian dermatologist, who first described it in 1872. ‘Sarcoma’ (from ancient Greek ‘flesh’) means a cancerous growth starting from abnormal cells of connective tissue.

Kaposi’s sarcoma can be limited, only affecting the skin, or more extensive with involvement of lymph nodes and internal organs such as the lungs or digestive system. It may be chronic which means it slowly gets worse, or it may rapidly worsen.

• Kaposi's sarcoma - printable version

As a wound heals, scar tissue forms. Initially, the colour and texture may differ from the surrounding skin but this usually flattens and fades with time. It is not uncommon for a scar to become slightly thick and raised. This is called a hypertrophic scar. However, a keloid (also called a keloid scar) is the name given to a scar that overgrows and becomes larger than the original wound. Unlike hypertrophic scars, keloids:

• Can develop after very minor skin damage, such as an acne spot, or sometimes without any obvious trauma to the skin (spontaneous keloids);
• Spread beyond the original area of skin damage;
• May be permanent.

• Keloids - printable version

KA is a relatively common, rapidly growing skin growth that usually develops on sun-exposed skin. It starts in skin cells that surround the hair follicle. Early diagnosis is needed to differentiate a keratoacanthoma from a skin cancer called squamous cell carcinoma (SCC). However, unlike an SCC, a keratoacanthoma is benign.  

• Keratoacanthoma - printable version

Keratosis pilaris (KP) is a very common and may be present in half the population. It is a completely harmless skin condition. It affects 50-70% of adolescents and approximately 40% of adults. Its name gives some idea of what it is; ‘keratosis’ means that there is too much keratin, which makes up the tough horny outer layer of the skin, while ‘pilaris’ comes from the Latin for hair (pilus). In keratosis pilaris, many small (1 to 2 mm across) horny plugs can be seen blocking the hair follicles on the upper and outer parts of the arms and thighs. This can look like goose bumps but feels slightly rough. Keratosis pilaris appears when extra keratin accumulates in the hair follicles. This usually starts in childhood and becomes more obvious during adolescence and in adulthood. For reasons not fully understood the condition seems to be better in the summer than in the winter perhaps because in winter the skin often gets dry while in summer the sweat makes it less dry. Keratosis pilaris may be associated with ichthyosis vulgaris and atopic eczema, however this may be coincidental.

• Keratosis pilaris - printable version

Latex is a milky sap from plants like the tropical rubber tree. It contains a mixture of water, sugar and proteins. The sap is collected by drilling into the tree and used to make rubber items such as household gloves and medical gloves, shoes, tyres, balloons and condoms. During the manufacturing process chemicals such as accelerators are added to harden it and the rubber item is heated then finally rinsed.  The finished item, in addition to latex, may contain residual added (non-latex) proteins and chemicals and these can also cause allergic reactions.     

• Latex Allergy

Lentigo maligna is one type of the earliest stage of a skin cancer called melanoma.

The word ‘melanoma’ comes from the Greek word ‘melas’, meaning black. Melanin is the dark pigment that gives the skin its natural colour and is made in the skin by pigment cells called melanocytes. After our skin is exposed to sunlight, the melanocytes make more melanin, and so the skin becomes darker.

Melanocytes may grow together in harmless groups or clusters, which are known as moles. Most people have between 10 and 50 moles and often they are darker than the surrounding skin.

Melanomas can arise in or near to a mole, but can also appear on skin that looks quite normal. They develop when the skin pigment cells (melanocytes) become cancerous and multiply in an uncontrolled way. They can then invade the skin around them and may also spread to other areas such as the lymph nodes, liver and lungs.

Lentigo maligna is a type of melanoma called ‘in situ’ melanoma. ‘In situ’ means that the cancer cells have not had the opportunity to spread anywhere else in the body. There are cancer cells in the top layer of the skin (the epidermis) but they are all contained in the area in which they began to develop. They have not started to spread or grow (‘invade’) into deeper layers of theskin. This is why some doctors call in situ cancers ‘pre-cancer’.

Lentigo maligna is a slow growing condition which can take years to develop. It appears in skin that has had a lot of sun exposure, usually the face, neck or upper arms.

Lentigo maligna can be cured with surgery. However, if the whole area is not removed completely with the appropriate surgery, some may develop into an invasive melanoma. It is therefore important to have it removed with a rim of normal skin (an adequate surgical margin). There are also preventative measures which can be taken (see below) that will further lower the risk of recurrence in the future.

• Lentigo maligna - printable version

Lichen planopilaris is a type of scarring hair loss that occurs when a relatively common skin disease, known as lichen planus, affects areas of skin where there is hair. Lichen planopilaris destroys the hair follicle and then replaces it with scarring, resulting in permanent hair loss. Lichen planopilaris can be divided into three different subtypes (see below). It is between 2 and 5 times more common in women than it is in men with the commonest age of onset being in the mid-40s.

• Lichen planopilaris - printable version

In dermatology, the word ‘lichen’ means small bumps on the skin and ‘planus’ means ‘flat’, so the name comes from a description of the rash’s appearance. Lichen planusis a fairly common (0.2-1% of the population worldwide), itchy, non-contagious rash that usually occurs in adults between the ages of 40 to 60. It is rare in children. It affects all ethnicities equally; however oral disease affecting the lips and inside the mouth, may be more common in patients from the Indian subcontinent originally.

• Lichen planus - printable version

Lichen sclerosus is a chronic inflammatory skin condition which can affect any part of the skin, but it most often affects the genital skin (vulva) and the skin around the anus. It can start in childhood - or adulthood (usually after the menopause) and affect girls or women of any age.

• Lichen sclerosus (female) - printable version

Lichen sclerosus is a chronic inflammatory skin condition which can affect any part of the skin, but in men is most often seen on the foreskin and tip of the penis. It can affect boys or men of any age.

In some people, lichen sclerosus also affects the skin elsewhere on the body, where it can cause whitish patches of skin, but usually no discomfort.

• Lichen sclerosus (male) - printable version

Lichen sclerosus is an inflammatory skin condition. It mainly tends to affect the genital areas (vulva and penis). The cause is not known, but it may be a form of autoimmune disease (when the immune system attacks healthy cells in the body by mistake) and can run in families.

• Lichen sclerosus in female children

The term ‘lichen’ is Latin and means a plant-like moss covering trees. Lichen simplex describes a response to the skin being repeatedly scratched or rubbed over a long period of time (also called lichen simplex chronicus). A single or multiple plaque (thickened area of skin) of rough skin forms, with increased markings and sometimes little bumps around the hair follicles.

Lichen simplex can affect any age group, but is most common in adults and is unusual in children.

• Lichen simplex - printable version

Linear IgA disease is a very rare blistering condition of the skin in adults. A similar condition affecting children is known as Chronic Bullous Disease of Childhood (CBDC).

The condition is called ‘Linear IgA disease’ because a type of protein called  immunoglobulin A (IgA) can be seen deposited under the outer layer of the skin (the epidermis) in a line (linear) when a small sample of skin biopsy is prepared specially and examined under the microscope. 

• Linear IgA disease - printable version

Lymphoedema is a long-term swelling that develops because of a fault within the lymphatic drainage system. This may be as a result of the lymphatic system not developing properly, or because it has been damaged.

• Lymphoedema - printable version

Melanocytic naevi are pigmented moles. The word ‘melanocytic’ means that they are made up of the cells (melanocytes) which produce the dark pigment (melanin) that gives the skin its colour. Melanocytes clustered together form naevi. This type of moles vary in colour in different skin tones and they are easier to see on pink skins.

Some moles are present at birth or appear within first two years of life are known as congenital melanocytic naevi. Most develop during childhood and early adult life and are consequently called acquired melanocytic naevi. The number of moles increase up to the age of 30-40. Thereafter, the number of naevi tend to decrease. New moles appearing in adulthood need to be monitored and checked if growing or changing. Moles can be found anywhere on the skin, including on the hands and feet, genitals, eyes and scalp.

• Melanocytic naevi - printable version

Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. One of the main causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanocytes make a brown/black pigment (known as melanin), and often the first sign of a melanoma developing is a previous mole changing in colour or a new brown/black lesion developing on the skin. Most frequently there is darkening in colour but occasionally there is loss of pigmentation with pale areas or red areas developing. Occasionally melanomas have no pigment and appear just a pink/red colour. The development of this melanoma on the skin is known as the primary melanoma.

Melanoma is considered to be the most serious type of skin cancer. This is because it is more likely to spread (metastasise) from the skin to other parts of the body than other types of skin cancer. If melanoma has spread to other parts of the body, those deposits are known as secondary melanoma (secondaries/metastases). Although a diagnosis of melanoma can be serious, most melanomas are diagnosed at an early stage and so do not cause any further problem. If lesions are not removed caught at the early stages then there is a higher risk of the melanoma spreading, which can reduce life expectancy.

• Melanoma stage 1 - printable version

Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanoma is considered to be the most serious type of skin cancer because it is more likely to spread (metastasise) from the skin to other parts of the body than other types of skin cancer. If melanoma has spread to other parts of the body, those deposits are known as secondary melanoma (secondaries/metastases). Although a diagnosis of melanoma can be serious, most melanomas are diagnosed at an early stage and so do not cause any further problem. If lesions are not removed at the early stages then there is a higher risk of the melanoma spreading, which can reduce life expectancy.

• Melanoma - Stage 1B printable version

Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanocytes make a brown/black pigment (known as melanin), and often the first sign of a melanoma developing is a previous mole changing in colour or a new brown/black lesion developing on the skin. Most frequently there is darkening in colour but occasionally there is loss of pigmentation with pale areas or red areas developing. Occasionally melanomas have no pigment and appear just a pink/red colour. The development of this melanoma on the skin is known as the primary melanoma.

Melanoma is considered to be the most serious type of skin cancer because it is more likely to spread (metastasise) from the skin to other parts of the body than other types of skin cancer. If melanoma has spread to other parts of the body, those deposits are known as secondary melanoma (secondaries/metastases). Although a diagnosis of melanoma can be serious, most melanomas are caught at an early stage and so do not cause any further problem. If lesions are not caught at the early stages then there is a higher risk of the melanoma spreading, which can reduce life expectancy.

• Melanoma stage 2 - printable version

Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanocytes make a brown/black pigment (known as melanin), and often the first sign of a melanoma developing is a previous mole changing in colour or a new brown/black lesion developing on the skin. Most frequently there is darkening in colour but occasionally there is loss of pigmentation with pale areas or red areas developing. Occasionally melanomas have no pigment and appear just a pink/red colour. The development of this melanoma on the skin is known as the primary melanoma.

Melanoma is considered to be the most serious type of skin cancer because it is more likely to spread (metastasise) from the skin to other parts of the body than other types of skin cancer. If melanoma has spread to other parts of the body, those deposits are known as secondary melanoma (secondaries/metastases).

• Melanoma stage 3 - printable version

Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanocytes make a brown/black pigment (known as melanin), and often the first sign of a melanoma developing is a previous mole changing in colour or a new brown/black lesion developing on the skin. Most frequently there is darkening in colour but occasionally there is loss of pigmentation with pale areas or red areas developing. Occasionally melanomas have no pigment and appear just a pink/red colour. The development of this melanoma on the skin is known as the primary melanoma.

Melanoma is considered to be the most serious type of skin cancer because it is more likely to spread (metastasise) from the skin to other parts of the body than other types of skin cancer. If melanoma has spread to other parts of the body, those deposits are known as secondary melanoma (secondaries/metastases). 

• Melanoma stage 4 - printable version

Melanoma in situ is the very earliest stage of a skin cancer called melanoma. ‘In situ’ is Latin for ‘in space’. It means that the cancer cells have not had the opportunity to spread to anywhere else in the body.

About 7,000 people in the UK are diagnosed with melanoma each year. The word ‘melanoma’ comes from the Greek word ‘melas’, meaning black. Melanin is the pigment that gives the skin its natural colour. Melanin is made in the skin by pigment cells called melanocytes. After our skin is exposed to sunlight, the melanocytes make more melanin, and so the skin becomes darker.

Melanocytes sometimes grow together in harmless groups or clusters, which are known as moles. Most people have between 10 and 50 moles and often they are darker than the surrounding skin.

Melanomas can arise in or near to a mole but can also appear on skin that looks normal. They develop when the skin pigment cells (melanocytes) become cancerous and multiply in an uncontrolled way. They can then invade the skin around them and may also spread to other areas such as the lymph nodes, liver and lungs.

In melanoma in situ, cancer cells are confined to the top layer of the skin (the epidermis) and are all contained in the area in which they began to develop. They have not started to spread or grow into deeper layers of the skin and have not become invasive. The outlook is excellent.This is because there are no blood or lymphatic channels in the top layer of the skin via which the abnormal cells can spread.  Some doctors call in situ cancers ‘pre-cancer’.

Melanoma in situcan be cured if it is cut out (excised) completely. However, if not removed with appropriate surgery, it can develop into an invasive cancer. This is why it is important to have melanoma in situ removed with a small rim of normal skin (an adequate surgical margin) and to know about preventative measures you can take which will lower your risk of another melanoma in the future.

• Melanoma in situ - printable version

Melasma, also called ‘chloasma’ and ‘pregnancy mask’, is a common skin condition of adults in which brown or greyish patches of pigmentation (colour) develop, usually on the face. The name comes from melas, the Greek word for black, or cholas, from the word green-ish. It is more common in women, particularly during pregnancy (when up to 50% of women may be affected). Sometimes men may also be affected. Melasma is more common in people of colour and those who tan very quickly but can occur to anyone.

Melasma usually becomes more noticeable in the summer and improves during the winter months.It is not an infection; therefore, it is not contagious, and it is not due to an allergy. It is not cancerous and will not develop into skin cancer.

• Melasma - printable version

Mepacrine was originally introduced as a treatment for malaria and for certain other tropical infections. It is an unlicensed medication in the United Kingdom. It is one of several antimalarial drugs that have also been found to have anti-inflammatory properties, which can help some skin conditions.

• Mepacrine - printable version

Methotrexate is a type of medicine called an immunosuppressant. This means it suppresses the body’s immune system and lowers immunity. The immune system is important in fighting infections, but sometimes immune system cells mistakenly attack the body’s own healthy tissues, triggering long-term inflammation. Methotrexate reduces the inflammation caused by your condition by dampening down the activity of these cells in the immune system. 

• Methotrexate - printable version

Mohs’ micrographic surgery was first developed by Dr Frederic Mohs in the 1930s. It is a specialised surgical method for removing certain types of skin cancer – usually basal cell cancers (BCC) and squamous cell cancers (SCC).

During the Mohs’ micrographic surgery procedure, the ‘roots’ of the skin cancer are located and removed.  This is done in stages by removing the tumour together with a thin (1-2mm) layer of surrounding normal tissue.  After each stage the tissue is frozen and cut into thin slices that are then stained with a dye. The edges are then examined very carefully under the microscope.  If the tumour is found at the edge of the slice, then a further slice of tissue is removed, but only in the area where the tumour remains.  Therefore, close to 100% of the cancer is located and removed.

Sometimes, if the tissue cannot be processed by same-day frozen sections, it is necessary to perform these stages several days apart – this may be recommended in other, more unusual, conditions such as lentigo maligna (slow Mohs’). 

There are two main advantages of removing the skin layer by Mohs’ surgery.  Firstly, the minimum of healthy skin is removed around the skin cancer, which keeps the wound as small as possible (‘tissue sparing’). Secondly, your dermatological surgeon can be almost certain that the skin cancer is fully removed on the day of the procedure. The disadvantages of Mohs’ are that waiting times for Mohs’ are often longer than for standard excision, as it is a longer procedure (often involving several stages in one day) and not all skin cancers are suitable for removal by Mohs’. 

Non-Mohs’ minor operations (called standard excision) also surgically remove skin cancers together with an area of healthy unaffected surrounding skin and some subcutaneous tissue below it.  However, the area is usually around 4mm (slightly larger than for Mohs’). Once removed, the skin is sent to the laboratory for examination by a pathologist (a doctor who specialises in looking at the tissue cells with a microscope) to confirm whether the operation has been successful or not. It usually takes about 2 weeks for a pathology report to be available. The report will state whether the skin cancer appears to have been fully removed or not.  If it has not been completely removed, a further procedure may be necessary.  However, with a standard excision the pathologist is only able to look at a small proportion of the cut area (usually, less than 2% of the area).  This means that the pathologist’s report is an estimation of the completeness of removal.  We know that (depending on the type of skin cancer) standard excision is sufficient to prevent the tumour coming back around 80-95% of the time. 

Therefore, standard excision is a good option for many patients.  However, for patients who have skin cancers on the face, or have certain types of tumours, your doctor may recommend Mohs’ Surgery.  

Mohs’ procedure is performed by dermatologists or dermatological surgeons who are specially trained in Mohs’ micrographic surgery. This training is an additional 1-2 years over that required to become a consultant dermatologist.  The British Association of Dermatologists, in conjunction with the British Society for Dermatological Surgery, have published standards on Mohs’ micrographic surgery and a link to these standards can be found below.

In the NHS, dermatologists and Mohs’ surgeons who are undergoing specialized training may be involved in your care, under the supervision of a consultant Mohs’ surgeon.  Occasionally, support may be given by other specialists, eg a plastic surgeon to help remove the tumour or reconstruct the wound, an oculoplastic surgeon for the eye area, or a head and neck surgeon to treat the deepest part of the cancer.

• Mohs surgery - printable version

Molluscum contagiosum is caused by a pox virus. It can spread to others if the spots are in direct contact with someone else or they share the same item such as a towel. The spots usually appear a few weeks later. They are more common and extensive in people who have eczema. Sometimes people whose immune system is suppressed for any reason, such as by HIV infection or through taking immunosuppressive treatments may develop large numbers of molluscum spots, but most people with molluscum contagiosum are generally in good health.

• Molluscum contagiosum - printable version

Morphoea is a rare skin disorder where areas of skin become much thicker and firmer than normal. It is sometimes called ‘localised scleroderma.’ This term originates from two words ‘sklero’ meaning ‘hard’ and ‘derma’ meaning skin. It should not be confused with systemic sclerosis, which is a different disease that affects internal organs and the blood circulation as well as the skin. Morphoea usually affects a few small areas of the skin. Very rarely, it can occur over larger areas of the body in a form called ‘generalised morphoea.’ 

• Morphoea and localised scleroderma - printable version

MMP is the most up-to-date term for this condition. Other names include cicatricial pemphigoid, oral pemphigoid and ocular pemphigoid.

MMP is an uncommon blistering condition which most frequently affects the lining of the mouth and gums. Other moist surfaces of the body (known as mucous membranes) can also be affected, and these include the surface layers of the eyes, the inside of the nose, the throat and the genitalia. The skin is sometimes affected by a few scattered blisters. MMP usually starts in middle and old age. Although it is not usually a serious condition in the mouth, the diagnosis of any type of MMP is important as it will alert your specialist to the possibility that the condition may involve your eyes, even if you have no symptoms. Eye involvement (known as ocular cicatricial pemphigoid or ocular MMP) does not occur in all people with MMP, but is potentially serious as it may cause scarring and affect your eyesight.  Scarring may also affect the throat and the genitalia, and may be very serious if the larynx is affected.

• Mucous membrane pemphigoid - printable version

Mycophenolate mofetil (MMF) is a medicine that is mainly used to stop the body from rejecting a transplanted organ (e.g. kidney, heart and liver). MMF can also be used to treat skin conditions. It reduces the action of the body’s own defence system (the immune system) and is one of a group of drugs known as immunosuppressive agents. It is used in certain skin conditions in which the immune system loses control and begins to act against the body. 

• Mycophenolate mofetil - printable version

Mycosis fungoides is a type of cutaneous or skin lymphoma. It is the commonest of a group of conditions known as cutaneous T-cell lymphomas. Cutaneous T-cell lymphomas are cancers that affect the skin and are caused by uncontrolled growth of the T-cell lymphocytes in the skin. T cell lymphocytes are white blood cells that can be found all over the body and in the blood stream.

Mycosis fungoides is a rare condition. Each year in the UK, approximately 450 people are newly diagnosed with mycosis fungoides. Most affected people live a normal life span.  

Mycosis fungoides can occur at any age but it most often starts between the ages of 50 and 70 years.

• Mycosis fungoides - printable version

Necrobiosis lipoidica is an uncommon inflammatory condition in which shiny, reddish-brown or yellowish patches develop in the skin, usually in young adults and early middle age. The condition is most commonly seen in conjunction with diabetes - both the insulin-dependent type 1 and non-insulin-dependent type 2, but it can also occur in non-diabetic people as well.

• Necrobiosis lipoidica - printable version

Nicotinamide is a form of vitamin B3. It can be taken as tablets to prevent and treat niacin deficiency (pellagra). Nicotinamide has protective effects against skin damage caused by ultraviolet (UV) radiation.

• Nicotinamide - printable version

‘Pruritus’ is the word doctors often use for itching. ‘Prurigo’ is a related word, which describes the changes that appear in the skin after it has been itched and scratched for a long time. In nodular prurigo these changes look like firm very itchy bumps (nodules) on the skin’s surface. These can improve or resolve when the person stops scratching the area, although for many people this can be very difficult without proper and sometimes prolonged medical treatment.

• Nodular prurigo - printable version

Omalizumab is a drug that has been specially designed to mimic normal human molecules, and for this reason is classified as a biologic drug. It interferes with natural antibodies called IgEs in the body and prevents them from causing histamine release from certain cells.

• Omalizumab

Lichen planus is an inflammatory condition of the skin but can also affect the mouth (oral lichen planus). Oral lichen planus may occur on its own or in combination with lichen planus of the skin, nails or genitals. It is thought to affect 1 to 2% per cent of the population, and typically affects women after the age of 40 years. Oral lichen planus can occur in men, but children are rarely affected.

• Oral lichen planus - printable version

Oral treatment with corticosteroids is also known as ‘oral cortisone therapy’ or ‘systemic steroid therapy’. The word ‘oral’ means that the steroids are taken by mouth, usually in tablet or liquid form.

Corticosteroids (also known as steroids) are chemicals (hormones) that occur naturally in the body. They have numerous roles in the body which include decreasing inflammation and suppressing the body's immune system. Corticosteroid medicines are man-made but are similar to these natural hormones. Corticosteroids are produced in the cortex (outer layer) of the adrenal glands (hence the ‘cortico-’ part of the name).

The corticosteroids used most often in medical treatment, prednisolone and dexamethasone, are not exactly the same as the ones produced in the body. It is convenient to refer to them just as ‘corticosteroids’ or 'steroids', but you should be aware that they are different from the type of steroids (anabolic steroids) used for body building.        

• Oral treatment with corticosteroids - printable version