Rare Nephrology News

Disease Profile

Proliferating trichilemmal cyst

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Proliferating pilar cyst


Rare Cancers; Skin Diseases


Proliferating trichilemmal tumor (PTT) is a benign tumor originating from the hair follicle. Although it is a benign tumor, PTT may be locally aggressive and in very rare cases the tumor may become malignant. In most cases there is only one lesion and occur in elderly women.[1][2] The tumor is not painful but sometimes they may grow very large and pressure and damage the skin around it resulting in wounds and foul-smelling discharge. About 90% of the cases are on the scalp, but they have also been found on the forehead, nose, back, chest, abdomen, buttocks, elbow, wrist and genitalia.[3] Treatment is with surgery removing the lesion. Prognosis is good in most cases but the patient should be followed closely after surgery.[2]


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Epidermoid cyst
Skin cyst
Skin ulcer
Open skin sore
30%-79% of people have these symptoms
Sparse scalp hair
Reduced/lack of hair on scalp
Scalp hair, thinning
Sparse, thin scalp hair
sparse-absent scalp hair

[ more ]


Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.


  1. Proliferating trichilemmal cyst. DermnetNZ. 2016; https://www.dermnetnz.org/lesions/proliferating-trichilemmal-cyst.html.
  2. Vatanchi M. Proliferating Pilar Tumor Treatment & Management. Proliferating Pilar Tumor Treatment & Management.. Medscape Reference. September 16, 2015; https://emedicine.medscape.com/article/1060682-treatment.
  3. Goyal S, Jain BB, Jana S & Bhattacharya SK. Malignant Proliferating Trichilemmal Tumor. Indian J Dermatol. January, 2012; 57(1):50–52. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312659/.