Cowden syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Cowden syndrome is a genetic disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers.

Almost everyone with Cowden syndrome develops hamartomas. These growths are most commonly found on the skin and mucous membranes (such as the lining of the mouth and nose), but they can also occur in the intestine and other parts of the body. The growth of hamartomas on the skin and mucous membranes typically becomes apparent by a person's late twenties.

Cowden syndrome is associated with an increased risk of developing several types of cancer, particularly cancers of the breast, a gland in the lower neck called the thyroid, and the lining of the uterus (the endometrium). Other cancers that have been identified in people with Cowden syndrome include kidney cancer, colorectal cancer, and an agressive form of skin cancer called melanoma. Compared with the general population, people with Cowden syndrome develop these cancers at younger ages, often beginning in their thirties or forties. People with Cowden syndrome are also more likely to develop more than one cancer during their lifetimes compared to the general population. Other diseases of the breast, thyroid, and endometrium are also common in Cowden syndrome. Additional signs and symptoms can include an enlarged head (macrocephaly) and a rare, noncancerous brain tumor called Lhermitte-Duclos disease. A small percentage of affected individuals have delayed development, intellectual disability, or autism spectrum disorder, which can affect communication and social interaction.

Some people do not meet the strict criteria for a clinical diagnosis of Cowden syndrome, but they have some of the characteristic features of the condition, particularly the cancers. These individuals are often described as having Cowden-like syndrome. Both Cowden syndrome and Cowden-like syndrome are caused by mutations in the same genes.

The features of Cowden syndrome overlap with those of another disorder called Bannayan-Riley-Ruvalcaba syndrome. People with Bannayan-Riley-Ruvalcaba syndrome also develop hamartomas and other noncancerous tumors. Some people with Cowden syndrome have relatives diagnosed with Bannayan-Riley-Ruvalcaba syndrome, and other affected individuals have the characteristic features of both conditions. Based on these similarities, researchers have proposed that Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome represent a spectrum of overlapping features known as PTEN hamartoma tumor syndrome (named for the genetic cause of the conditions) instead of two distinct conditions.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Changes in the PTEN, KLLN, or WWP1 gene are most commonly identified in people with Cowden syndrome or Cowden-like syndrome.

About 25 percent of Cowden syndrome and a small percentage of cases of Cowden-like syndrome result from mutations in the PTEN gene. The protein produced from the PTEN gene is a tumor suppressor, which means that it normally prevents cells from growing and dividing (proliferating) too rapidly or in an uncontrolled way. Mutations in the PTEN gene prevent the PTEN protein from regulating cell proliferation effectively, leading to uncontrolled cell division and the formation of hamartomas and cancerous tumors. The PTEN gene likely has other important functions within cells; however, research is needed to determine what role mutations in this gene play in causing the other features of Cowden syndrome, such as macrocephaly and intellectual disability.

Rarely, Cowden syndrome and Cowden-like syndrome result from a change involving the KLLN gene. This gene provides instructions for making a protein called killin. Like the protein produced from the PTEN gene, killin probably acts as a tumor suppressor. The genetic change that causes Cowden syndrome and Cowden-like syndrome leads to reduced production of the killin protein. A reduced amount of killin may allow abnormal cells to survive and proliferate inappropriately, which can lead to the formation of tumors.

A small percentage of Cowden syndrome and Cowden-like syndrome are associated with variants in the WWP1 gene. The WWP1 gene provides instructions for making a protein that is involved in the process that targets other proteins to be broken down (degraded) within cells. During this process, the WWP1 protein attaches (binds) to the PTEN protein, which impairs PTEN's function. WWP1 gene variants are described as "gain-of-function" because they appear to enhance the activity of the WWP1 protein. Studies suggest that the altered protein binds to the PTEN protein more readily than normal. Excessive binding impairs PTEN's tumor suppressor activity, allowing cells to proliferate unchecked and, leading to the formation of tumors.

Mutations in a few other genes are each responsible for a very small percentage of cases of Cowden syndrome and Cowden-like syndrome. In the remaining cases, the genetic cause is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Cowden syndrome and Cowden-like syndrome are inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the condition and increase the risk of developing cancer. In some cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Although the exact prevalence of Cowden syndrome is unknown, researchers estimate that it affects about 1 in 200,000 people.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Breast carcinoma · Very frequent (99-80%)

The presence of a carcinoma of the breast.

Colorectal polyposis · Very frequent (99-80%)

Multiple abnormal growths that arise from the lining of the large intestine (colon or rectum) and protrude into the intestinal lumen.

Conjunctival hamartoma · Very frequent (99-80%)

A hamartoma (disordered proliferation of mature tissues) of the conjunctiva.

Goiter · Very frequent (99-80%)

An enlargement of the thyroid gland.

Macule · Very frequent (99-80%)

A flat, distinct, discolored area of skin less than 1 cm wide that does not involve any change in the thickness or texture of the skin.

Neoplasm of the skin · Very frequent (99-80%)

A tumor (abnormal growth of tissue) of the skin.

Palmoplantar keratoderma · Very frequent (99-80%)

Abnormal thickening of the skin of the palms of the hands and the soles of the feet.

Papilloma · Very frequent (99-80%)

A tumor of the skin or mucous membrane with finger-like projections.

Other findings in the same source

From: Orphanet

Additional reported features include Papule (Very frequent (99-80%)); Generalized hyperkeratosis (Very frequent (99-80%)); Abnormality of the penis (Frequent (79-30%)); Abnormality of the thyroid gland (Frequent (79-30%)); Adenoma sebaceum (Frequent (79-30%)); Ataxia (Frequent (79-30%)); Cavernous hemangioma (Frequent (79-30%)); Cognitive impairment (Frequent (79-30%)); Fibroma (Frequent (79-30%)); Furrowed tongue (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Cowden syndrome 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 Cowden syndrome. 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.