Cowden syndrome-1 is a hamartomatous disorder characterized by macrocephaly, facial trichilemmomas, acral keratoses, papillomatous papules, and an increased risk for the development of breast, thyroid, and endometrial carcinoma. Bannayan-Riley-Ruvalcaba syndrome (BRRS), previously thought be distinct, shared clinical characteristics with Cowden syndrome, such as hamartomatous polyps of the gastrointestinal tract, mucocutaneous lesions, and increased risk of developing neoplasms, but had the additional features of developmental delay, macrocephaly, lipomas, hemangiomas, and pigmented speckled macules of the glans penis in males. Because features of BRRS and Cowden syndrome have been found in individuals within the same family with the same PTEN mutation, Cowden syndrome-1 and BRRS are considered to be the same disorder with variable expression and age-related penetrance (summary by Marsh et al., 1999, Lachlan et al., 2007, and Blumenthal and Dennis, 2008). Approximately 80% of patients reported with Cowden syndrome and 60% with BRSS have PTEN mutations (Blumenthal and Dennis, 2008). Some patients with Cowden syndrome may have immune system defects resulting in increased susceptibility to infections (summary by Browning et al., 2015).

Melkersson-Rosenthal syndrome is characterized by chronic swelling of the face, peripheral facial palsy, which may be bilateral and may tend to relapse, and in some cases ligua plicata (fissured tongue). The swelling is localized especially to the lips. Onset is usually in childhood or adolescence (summary by Kunstadter, 1965).

Keratitis-ichthyosis-deafness (KID) syndrome is a rare ectodermal dysplasia characterized by sensorineural hearing loss, photophobia and corneal vascularization, hyperkeratosis of the palms and soles, erythrokeratoderma, follicular hyperkeratosis, and recurrent bacterial and fungal infections. A subset of patients with KID may develop multiple cystic pilar tumors, which are prone to malignant transformation and metastasis (Nyquist et al., 2007). Vohwinkel syndrome (124500) is an allelic disorder involving congenital deafness with keratopachydermia and constrictions of fingers and toes. Another similar disorder caused by mutation in GJB2 is palmoplantar keratoderma with deafness (148350). Genetic Heterogeneity of Keratitis-Ichthyosis-Deafness Syndrome An autosomal recessive form of KID syndrome (KIDAR; 242150) is caused by mutation in the AP1B1 gene (600157) on chromosome 22q12.

Bazex-Dupre-Christol syndrome (BDCS) is an X-linked dominant disorder characterized by a triad of congenital hypotrichosis, follicular atrophoderma affecting the dorsa of the hands and feet, the face, and extensor surfaces of the elbows or knees, and the development of basal cell neoplasms, including basal cell nevi and basal cell carcinomas from the second decade onward (Yung and Newton-Bishop, 2005). Rombo syndrome (180730) has similar features, but shows autosomal dominant inheritance.

A rare, genetic, chronic, recurrent, slowly progressive, epidermal disease characterized by small, sterile, pustular eruptions, involving the nails and surrounding skin of the fingers and/or toes, which coalesce and burst, leaving erythematous, atrophic skin where new pustules develop. Onychodystrophy is frequently associated and anonychia and osteolysis are reported in severe cases. Local expansion (to involve the hands, forearms and/or feet) and involvement of mucosal surfaces (e.g. conjunctiva, tongue, urethra) may be observed.

Hereditary mucoepithelial dysplasia (HMD) is a rare autosomal dominant genodermatosis characterized by onset in infancy of a panepithelial defect involving the oral, nasal, conjunctival, vaginal, cervical, perineal, urethral, and bladder mucosa. Patients develop cataracts, blindness, nonscarring alopecia, perineal psoriasiform lesions, and follicular keratoses (Witkop et al., 1982). Although 1 family was reported to have progressive severe interstitial lung disease (Witkop et al., 1979), this feature has not been reported in other families and is not considered a criterion for diagnosis. However, the clinical triad of nonscarring alopecia, well-demarcated fiery red mucosa, and psoriasiform perineal involvement has been consistently observed (review by Boralevi et al., 2005).

Ophthalmoplegia-intellectual disability-lingua scrotalis syndrome is a rare, genetic, syndromic intellectual disability disorder characterized by congenital, external, nuclear ophthalmoplegia, lingua scrotalis, progressive chorioretinal sclerosis and intellectual disability. Bilateral ptosis, bilateral facial weakness, Parinaud's syndrome, convergence paresis and myopia may be associated. There have been no further descriptions in the literature since 1975.

Claes-Jensen type of X-linked syndromic intellectual developmental disorder (MRXSCJ) is characterized by impaired intellectual development with substantial clinical heterogeneity in affected males. However, males are usually reported to have short stature, microcephaly, hyperreflexia, and aggressive behavior. In rare cases, female carriers exhibit mildly impaired intellectual development or learning difficulties (summary by Guerra et al., 2020).

This autosomal recessive form of distal arthrogryposis, designated DA5D by McMillin et al. (2013), is characterized by severe camptodactyly of the hands, including adducted thumbs and wrists; mild camptodactyly of the toes; clubfoot and/or a calcaneovalgus deformity; extension contractures of the knee; unilateral ptosis or ptosis that is more severe on one side; a round-shaped face; arched eyebrows; a bulbous, upturned nose; and micrognathia. Notably, these patients do not have ophthalmoplegia. For a general phenotypic description and discussion of genetic heterogeneity of distal arthrogryposis, see DA1A (108120). For discussion of genetic heterogeneity of distal arthrogryposis type 5, see DA5 (108145).

PIK3CA-related overgrowth spectrum (PROS) encompasses a range of clinical findings in which the core features are congenital or early-childhood onset of segmental/focal overgrowth with or without cellular dysplasia. Prior to the identification of PIK3CA as the causative gene, PROS was separated into distinct clinical syndromes based on the tissues and/or organs involved (e.g., MCAP [megalencephaly-capillary malformation] syndrome and CLOVES [congenital lipomatous asymmetric overgrowth of the trunk, lymphatic, capillary, venous, and combined-type vascular malformations, epidermal nevi, skeletal and spinal anomalies] syndrome). The predominant areas of overgrowth include the brain, limbs (including fingers and toes), trunk (including abdomen and chest), and face, all usually in an asymmetric distribution. Generalized brain overgrowth may be accompanied by secondary overgrowth of specific brain structures resulting in ventriculomegaly, a markedly thick corpus callosum, and cerebellar tonsillar ectopia with crowding of the posterior fossa. Vascular malformations may include capillary, venous, and less frequently, arterial or mixed (capillary-lymphatic-venous or arteriovenous) malformations. Lymphatic malformations may be in various locations (internal and/or external) and can cause various clinical issues, including swelling, pain, and occasionally localized bleeding secondary to trauma. Lipomatous overgrowth may occur ipsilateral or contralateral to a vascular malformation, if present. The degree of intellectual disability appears to be mostly related to the presence and severity of seizures, cortical dysplasia (e.g., polymicrogyria), and hydrocephalus. Many children have feeding difficulties that are often multifactorial in nature. Endocrine issues affect a small number of individuals and most commonly include hypoglycemia (largely hypoinsulinemic hypoketotic hypoglycemia), hypothyroidism, and growth hormone deficiency.

\n\nThe 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.\n\nSome 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.\n\nCowden 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.\n\nAlmost 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.\n\nCowden syndrome is a genetic disorder characterized by multiple noncancerous, tumor-like growths called hamartomas and an increased risk of developing certain cancers.

Pachyonychia congenita (PC) is characterized by hypertrophic nail dystrophy, painful palmoplantar keratoderma and blistering, oral leukokeratosis, pilosebaceous cysts (including steatocystoma and vellus hair cysts), palmoplantar hyperhydrosis, and follicular keratoses on the trunk and extremities.

Basel-Vanagaite-Smirin-Yosef syndrome is an autosomal recessive multiple congenital anomaly disorder characterized by severely delayed psychomotor development resulting in mental retardation, as well as variable eye, brain, cardiac, and palatal abnormalities (summary by Basel-Vanagaite et al., 2015).

RERE-related disorders are characterized by neurodevelopmental problems with or without structural anomalies of the eyes, heart, kidneys, and genitourinary tract and mild sensorineural hearing loss. Hypotonia and feeding problems are common among affected individuals. Developmental delay and intellectual disability range from mild to profound. Behavior problems may include attention-deficit/hyperactivity disorder, self-injurious behavior, and autism spectrum disorder. A variety of eye anomalies (coloboma, optic nerve anomalies, microphthalmia, and/or Peter's anomaly) and vision issues (myopia, anisometropia, astigmatism, exotropia, esotropia) have been reported. Congenital heart defects, most commonly septal defects, have also been described. Genitourinary abnormalities include vesicoureteral reflux, and cryptorchidism and hypospadias in males. Sensorineural hearing loss can be unilateral or bilateral.