Mycosis fungoides

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Mycosis fungoides is the most common form of a type of blood cancer called cutaneous T-cell lymphoma. Cutaneous T-cell lymphomas occur when certain white blood cells, called T cells, become cancerous; these cancers characteristically affect the skin, causing different types of skin lesions. Although the skin is involved, the skin cells themselves are not cancerous. Mycosis fungoides usually occurs in adults over age 50, although affected children have been identified.

Mycosis fungoides may progress slowly through several stages, although not all people with the condition progress through all stages. Most affected individuals initially develop skin lesions called patches, which are flat, scaly, pink or red areas on the skin that can be itchy. Cancerous T cells, which cause the formation of patches, are found in these lesions. The skin cells themselves are not cancerous; the skin problems result when cancerous T cells move from the blood into the skin. Patches are most commonly found on the lower abdomen, upper thighs, buttocks, and breasts. They can disappear and reappear or remain stable over time. In some affected individuals, patches progress to plaques, the next stage of mycosis fungoides.

Plaques are raised lesions that are usually reddish, purplish, or brownish in color and itchy. Plaques commonly occur in the same body regions as patches. While some plaques arise from patches, others develop on their own, and an affected person can have both patches and plaques simultaneously. As with patches, cancerous T cells are found in plaques. Plaques can remain stable or can develop into tumors. Not everyone with patches or plaques develops tumors.

The tumors in mycosis fungoides, which are composed of cancerous T cells, are raised nodules that are thicker and deeper than plaques. They can arise from patches or plaques or occur on their own. Mycosis fungoides was so named because the tumors can resemble mushrooms, a type of fungus. Common locations for tumor development include the upper thighs and groin, breasts, armpits, and the crook of the elbow. Open sores may develop on the tumors, often leading to infection.

Although rare, the cancerous T cells can spread to other organs, including the lymph nodes, spleen, liver, and lungs. Spread to other organs can occur in any stage of mycosis fungoides but is most common in the tumor stage. In addition, affected individuals have an increased risk of developing another lymphoma or other type of cancer.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

The cause of mycosis fungoides is unknown. Most affected individuals have one or more chromosomal abnormalities, such as the loss or gain of genetic material. These abnormalities occur during a person's lifetime and are found only in the DNA of cancerous cells. Abnormalities have been found on most chromosomes, but some regions are more commonly affected than others. People with this condition tend to have additions of DNA in regions of chromosomes 7 and 17 or loss of DNA from regions of chromosomes 9 and 10. It is unclear whether these genetic changes play a role in mycosis fungoides, although the tendency to acquire chromosome abnormalities (chromosomal instability) is a feature of many cancers. It can lead to genetic changes that allow cells to grow and divide uncontrollably.

Other research suggests that certain variants of HLA class II genes are associated with mycosis fungoides. HLA genes help the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). Each HLA gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. The specific variants are inherited through families. Certain variations of HLA genes may affect the risk of developing mycosis fungoides or may impact progression of the disorder.

It is possible that other factors, such as environmental exposure or certain bacterial or viral infections, are involved in the development of mycosis fungoides. However, the influence of genetic and environmental factors on the development of this complex disorder remains unclear.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

The inheritance pattern of mycosis fungoides has not been determined. Although the condition has been found in multiple members of more than a dozen families, it most often occurs in people with no history of the disorder in their family and is typically not inherited.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Mycosis fungoides occurs in about 1 in 100,000 to 350,000 individuals. It accounts for approximately 70 percent of cutaneous T-cell lymphomas. For unknown reasons, mycosis fungoides affects males nearly twice as often as females. In the United States, there are an estimated 3.6 cases per million people each year. The condition has been found in regions around the world.

Which doctor should you see?

The suggested department for discussing Mycosis fungoides is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Mycosis fungoides. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.