What are the signs and symptoms of Cowden syndrome? Cowden syndrome is characterized primarily by multiple, noncancerous growths (called hamartomas) on various parts of the body. Approximately 99% of people affected by Cowden syndrome will have benign growths on the skin and/or in the mouth by the third decade of life. A majority of affected people will also develop growths (called hamartomatous polyps) along the inner lining of the gastrointestinal tract. People affected by Cowden syndrome also have an increased risk of developing certain types of cancer. Breast, thyroid and endometrial (the lining of the uterus) cancers are among the most commonly reported tumors. Other associated cancers include colorectal cancer, kidney cancer and melanoma. People with Cowden syndrome often develop cancers at earlier ages (before age 50) than people without a hereditary predisposition to cancer. Other signs and symptoms of Cowden syndrome may include benign diseases of the breast, thyroid, and endometrium; a rare, noncancerous brain tumor called Lhermitte-Duclos disease; an enlarged head (macrocephaly); autism spectrum disorder; intellectual disability; and vascular (the body's network of blood vessels) abnormalities. The Human Phenotype Ontology provides the following list of signs and symptoms for Cowden syndrome. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormality of the pupil 90% Abnormality of the tongue 90% Aplasia/Hypoplasia of the cerebellum 90% Arteriovenous malformation 90% Cognitive impairment 90% Conjunctival hamartoma 90% Dental malocclusion 90% Epibulbar dermoid 90% Exostoses 90% Foot polydactyly 90% Genu recurvatum 90% Incoordination 90% Increased intracranial pressure 90% Intestinal polyposis 90% Irregular hyperpigmentation 90% Lower limb asymmetry 90% Macrocephaly 90% Melanocytic nevus 90% Migraine 90% Myopia 90% Nausea and vomiting 90% Neoplasm of the breast 90% Neoplasm of the nervous system 90% Neoplasm of the thyroid gland 90% Seizures 90% Uterine neoplasm 90% Verrucae 90% Abnormality of the parathyroid gland 50% Abnormality of the penis 50% Abnormality of the teeth 50% Anemia 50% Cataract 50% Cavernous hemangioma 50% Communicating hydrocephalus 50% Dolichocephaly 50% Furrowed tongue 50% Gastrointestinal hemorrhage 50% Gingival overgrowth 50% Goiter 50% Heterochromia iridis 50% Hypermelanotic macule 50% Hyperostosis 50% Hypertrichosis 50% Mandibular prognathia 50% Meningioma 50% Mucosal telangiectasiae 50% Multiple lipomas 50% Palmoplantar keratoderma 50% Retinal detachment 50% Shagreen patch 50% Venous insufficiency 50% Intellectual disability 12% Intellectual disability, mild 12% Abnormality of neuronal migration 7.5% Abnormality of the palate 7.5% Abnormality of the retinal vasculature 7.5% Adenoma sebaceum 7.5% Anteverted nares 7.5% Autism 7.5% Bone cyst 7.5% Brachydactyly syndrome 7.5% Bronchogenic cyst 7.5% Cafe-au-lait spot 7.5% Gynecomastia 7.5% Hearing impairment 7.5% Hypopigmented skin patches 7.5% Kyphosis 7.5% Melanoma 7.5% Ovarian neoplasm 7.5% Pectus excavatum 7.5% Polycystic ovaries 7.5% Renal neoplasm 7.5% Scoliosis 7.5% Short stature 7.5% Skeletal dysplasia 7.5% Splenomegaly 7.5% Tall stature 7.5% Thymus hyperplasia 7.5% Abnormality of the cardiovascular system - Adult onset - Angioid streaks of the retina - Autosomal dominant inheritance - Breast carcinoma - Colonic diverticula - Fibroadenoma of the breast - Hamartomatous polyposis - High palate - Hydrocele testis - Hyperthyroidism - Hypoplasia of the maxilla - Hypothyroidism - Intention tremor - Narrow mouth - Ovarian cyst - Palmoplantar hyperkeratosis - Progressive macrocephaly - Skin tags - Subcutaneous lipoma - Thyroid adenoma - Thyroiditis - Transitional cell carcinoma of the bladder - Varicocele - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.