Multiple endocrine neoplasia type 1 (MEN1) includes varying combinations of more than 20 endocrine and non-endocrine tumors. Endocrine tumors become evident either by overproduction of hormones by the tumor or by growth of the tumor itself. Parathyroid tumors are the most common MEN1-associated endocrinopathy; onset in 90% of individuals is between ages 20 and 25 years with hypercalcemia evident by age 50 years; hypercalcemia causes lethargy, depression, confusion, anorexia, constipation, nausea, vomiting, diuresis, dehydration, hypercalciuria, kidney stones, increased bone resorption/fracture risk, hypertension, and shortened QT interval. Pituitary tumors include prolactinoma (the most common), which manifests as oligomenorrhea/amenorrhea and galactorrhea in females and sexual dysfunction in males. Well-differentiated endocrine tumors of the gastro-entero-pancreatic (GEP) tract can manifest as Zollinger-Ellison syndrome (gastrinoma); hypoglycemia (insulinoma); hyperglycemia, anorexia, glossitis, anemia, diarrhea, venous thrombosis, and skin rash (glucagonoma); and watery diarrhea, hypokalemia, and achlorhydria syndrome (vasoactive intestinal peptide [VIP]-secreting tumor). Carcinoid tumors are non-hormone-secreting and can manifest as a large mass after age 50 years. Adrenocortical tumors can be associated with primary hypercortisolism or hyperaldosteronism. Non-endocrine tumors include facial angiofibromas, collagenomas, lipomas, meningiomas, ependymomas, and leiomyomas.

Hereditary paraganglioma-pheochromocytoma (PGL/PCC) syndromes are characterized by paragangliomas (tumors that arise from neuroendocrine tissues distributed along the paravertebral axis from the base of the skull to the pelvis) and pheochromocytomas (paragangliomas that are confined to the adrenal medulla). Sympathetic paragangliomas cause catecholamine excess; parasympathetic paragangliomas are most often nonsecretory. Extra-adrenal parasympathetic paragangliomas are located predominantly in the skull base and neck (referred to as head and neck PGL [HNPGL]) and sometimes in the upper mediastinum; approximately 95% of such tumors are nonsecretory. In contrast, sympathetic extra-adrenal paragangliomas are generally confined to the lower mediastinum, abdomen, and pelvis, and are typically secretory. Pheochromocytomas, which arise from the adrenal medulla, typically lead to catecholamine excess. Symptoms of PGL/PCC result from either mass effects or catecholamine hypersecretion (e.g., sustained or paroxysmal elevations in blood pressure, headache, episodic profuse sweating, forceful palpitations, pallor, and apprehension or anxiety). The risk for developing metastatic disease is greater for extra-adrenal sympathetic paragangliomas than for pheochromocytomas.

Williams syndrome (WS) is characterized by cardiovascular disease (elastin arteriopathy, peripheral pulmonary stenosis, supravalvar aortic stenosis, hypertension), distinctive facies, connective tissue abnormalities, intellectual disability (usually mild), a specific cognitive profile, unique personality characteristics, growth abnormalities, and endocrine abnormalities (hypercalcemia, hypercalciuria, hypothyroidism, and early puberty). Feeding difficulties often lead to poor weight gain in infancy. Hypotonia and hyperextensible joints can result in delayed attainment of motor milestones.

The Murk Jansen type of metaphyseal chondrodysplasia is characterized by severe short stature, short bowed limbs, clinodactyly, prominent upper face, and small mandible. Hypercalcemia and hypophosphatemia occur despite the lack of parathyroid abnormalities (summary by Cohen, 2002).

Hypophosphatasia is characterized by defective mineralization of growing or remodeling bone, with or without root-intact tooth loss, in the presence of low activity of serum and bone alkaline phosphatase. Clinical features range from stillbirth without mineralized bone at the severe end to pathologic fractures of the lower extremities in later adulthood at the mild end. While the disease spectrum is a continuum, seven clinical forms of hypophosphatasia are usually recognized based on age at diagnosis and severity of features: Perinatal (severe): characterized by pulmonary insufficiency and hypercalcemia. Perinatal (benign): prenatal skeletal manifestations that slowly resolve into one of the milder forms. Infantile: onset between birth and age six months of clinical features of rickets without elevated serum alkaline phosphatase activity. Severe childhood (juvenile): variable presenting features progressing to rickets. Mild childhood: low bone mineral density for age, increased risk of fracture, and premature loss of primary teeth with intact roots. Adult: characterized by stress fractures and pseudofractures of the lower extremities in middle age, sometimes associated with early loss of adult dentition. Odontohypophosphatasia: characterized by premature exfoliation of primary teeth and/or severe dental caries without skeletal manifestations.

Blue Diaper syndrome is a hereditary metabolic disorder characterised by hypercalcaemia with nephrocalcinosis and indicanuria.

Familial hypocalciuric hypercalcemia (HHC) is a heritable disorder of mineral homeostasis that is transmitted as an autosomal dominant trait with a high degree of penetrance. HHC is characterized biochemically by lifelong elevation of serum calcium concentrations and is associated with inappropriately low urinary calcium excretion and a normal or mildly elevated circulating parathyroid hormone (PTH; 168450) level. Hypermagnesemia is typically present. Individuals with HHC are usually asymptomatic and the disorder is considered benign. However, chondrocalcinosis and pancreatitis occur in some adults (summary by Hannan et al., 2010). Characteristic features of familial hypocalciuric hypercalcemia include mild to moderate hypercalcemia, nonsuppressed parathyroid hormone, relative hypocalciuria while hypercalcemic (calcium/creatinine clearance ratio less than 0.01, or 24-hr urine calcium less than 6.25 mmol), almost 100% penetrance of hypercalcemia from birth, absence of complications, persistence of hypercalcemia following subtotal parathyroidectomy, and normal parathyroid size, weight, and histology at surgery. However, atypical presentations with severe hypercalcemia, hypercalciuria with or without nephrolithiasis or nephrocalcinosis, kindreds with affected members displaying either hypercalciuria or hypocalciuria, postoperative normocalcemia, and pancreatitis have all been described in FHH (Warner et al., 2004). Genetic Heterogeneity of Hypocalciuric Hypercalcemia Familial hypocalciuric hypercalcemia type II (HHC2; 145981) is caused by mutation in the GNA11 gene (139313) on chromosome 19p13, and HHC3 (600740) is caused by mutation in the AP2S1 gene (602242) on chromosome 19q13.

The spectrum of CDC73-related disorders includes the following phenotypes: Hyperparathyroidism-jaw tumor (HPT-JT) syndrome. Primary hyperparathyroidism, the main finding of HPT-JT syndrome, occurs in up to 95% of affected individuals; onset is typically in late adolescence or early adulthood. HPT-JT-associated primary hyperparathyroidism is usually caused by a single parathyroid adenoma. In approximately 10%-15% of individuals, primary hyperparathyroidism is caused by parathyroid carcinoma. Ossifying fibromas of the mandible or maxilla, also known as cementifying fibromas and cemento-ossifying fibromas, occur in 30%-40% of individuals with HPT-JT syndrome. Although benign, these tumors can be locally aggressive and may continue to enlarge if not treated. Approximately 20% of individuals with HPT-JT syndrome have kidney lesions, most commonly cysts; renal hamartomas and (more rarely) Wilms tumor have also been reported. Benign and malignant uterine tumors appear to be common in women with HPT-JT syndrome. Parathyroid carcinoma. Most parathyroid carcinomas are functional, resulting in hyperparathyroidism and a high serum calcium level; however, nonfunctioning parathyroid carcinomas are also rarely described in individuals with a CDC73-related disorder. A germline CDC73 pathogenic variant has been identified in 20%-29% of individuals with apparently sporadic parathyroid carcinoma. Familial isolated hyperparathyroidism (FIHP). FIHP is characterized by primary hyperparathyroidism without other associated syndromic features. Individuals with CDC73-related FIHP tend to have a more severe clinical presentation and younger age of onset than individuals with FIHP in whom a CDC73 pathogenic variant has not been identified.

The spectrum of CDC73-related disorders includes the following phenotypes: Hyperparathyroidism-jaw tumor (HPT-JT) syndrome. Primary hyperparathyroidism, the main finding of HPT-JT syndrome, occurs in up to 95% of affected individuals; onset is typically in late adolescence or early adulthood. HPT-JT-associated primary hyperparathyroidism is usually caused by a single parathyroid adenoma. In approximately 10%-15% of individuals, primary hyperparathyroidism is caused by parathyroid carcinoma. Ossifying fibromas of the mandible or maxilla, also known as cementifying fibromas and cemento-ossifying fibromas, occur in 30%-40% of individuals with HPT-JT syndrome. Although benign, these tumors can be locally aggressive and may continue to enlarge if not treated. Approximately 20% of individuals with HPT-JT syndrome have kidney lesions, most commonly cysts; renal hamartomas and (more rarely) Wilms tumor have also been reported. Benign and malignant uterine tumors appear to be common in women with HPT-JT syndrome. Parathyroid carcinoma. Most parathyroid carcinomas are functional, resulting in hyperparathyroidism and a high serum calcium level; however, nonfunctioning parathyroid carcinomas are also rarely described in individuals with a CDC73-related disorder. A germline CDC73 pathogenic variant has been identified in 20%-29% of individuals with apparently sporadic parathyroid carcinoma. Familial isolated hyperparathyroidism (FIHP). FIHP is characterized by primary hyperparathyroidism without other associated syndromic features. Individuals with CDC73-related FIHP tend to have a more severe clinical presentation and younger age of onset than individuals with FIHP in whom a CDC73 pathogenic variant has not been identified.

Neonatal severe hyperparathyroidism usually manifests in the first 6 months of life with severe hypercalcemia, bone demineralization, and failure to thrive. Early diagnosis is critical because untreated NSHPT can be a devastating neurodevelopmental disorder, which in some cases is lethal without parathyroidectomy. Some infants have milder hyperparathyroidism and a substantially milder clinical presentation and natural history (summary by Egbuna and Brown, 2008).

Any familial hypocalciuric hypercalcemia in which the cause of the disease is a mutation in the AP2S1 gene.

Familial hypocalciuric hypercalcemia type II (HHC2) is an autosomal dominant disorder characterized by lifelong elevations of serum calcium concentrations with low urinary calcium excretion and normal circulating parathyroid hormone concentrations in most patients. Patients are generally asymptomatic (summary by Nesbit et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of hypocalciuric hypercalcemia, see HHC1 (145980).

The spectrum of CDC73-related disorders includes the following phenotypes: Hyperparathyroidism-jaw tumor (HPT-JT) syndrome. Primary hyperparathyroidism, the main finding of HPT-JT syndrome, occurs in up to 95% of affected individuals; onset is typically in late adolescence or early adulthood. HPT-JT-associated primary hyperparathyroidism is usually caused by a single parathyroid adenoma. In approximately 10%-15% of individuals, primary hyperparathyroidism is caused by parathyroid carcinoma. Ossifying fibromas of the mandible or maxilla, also known as cementifying fibromas and cemento-ossifying fibromas, occur in 30%-40% of individuals with HPT-JT syndrome. Although benign, these tumors can be locally aggressive and may continue to enlarge if not treated. Approximately 20% of individuals with HPT-JT syndrome have kidney lesions, most commonly cysts; renal hamartomas and (more rarely) Wilms tumor have also been reported. Benign and malignant uterine tumors appear to be common in women with HPT-JT syndrome. Parathyroid carcinoma. Most parathyroid carcinomas are functional, resulting in hyperparathyroidism and a high serum calcium level; however, nonfunctioning parathyroid carcinomas are also rarely described in individuals with a CDC73-related disorder. A germline CDC73 pathogenic variant has been identified in 20%-29% of individuals with apparently sporadic parathyroid carcinoma. Familial isolated hyperparathyroidism (FIHP). FIHP is characterized by primary hyperparathyroidism without other associated syndromic features. Individuals with CDC73-related FIHP tend to have a more severe clinical presentation and younger age of onset than individuals with FIHP in whom a CDC73 pathogenic variant has not been identified.

IMAGe syndrome is an acronym for the major findings of intrauterine growth restriction (IUGR), metaphyseal dysplasia, adrenal hypoplasia congenita, and genitourinary abnormalities (in males). Findings reported in individuals with a clinical and/or molecular diagnosis include: IUGR; Some type of skeletal abnormality (most commonly delayed bone age and short stature, and occasionally, metaphyseal and epiphyseal dysplasia of varying severity); Adrenal insufficiency often presenting in the first month of life as an adrenal crisis or (rarely) later in childhood with failure to thrive and recurrent vomiting; Genital abnormalities in males (cryptorchidism, micropenis, and hypospadias) but not in females. Hypotonia and developmental delay are reported in some individuals; cognitive outcome appears to be normal in the majority of individuals.

Ulna metaphyseal dysplasia syndrome is a rare primary bone dysplasia characterized by dysplasia of the distal ulnar metaphyses, as well as metacarpal/metatarsal dysplasia and metaphyseal changes resembling enchondromata. Patients usually present bony swelling of the wrists with or without pain (knees and ankles may also be affected). Other variably associated features include platyspondyly, skeletal development delay, short stature and coxa valga.

Bartter syndrome refers to a group of disorders that are unified by autosomal recessive transmission of impaired salt reabsorption in the thick ascending loop of Henle with pronounced salt wasting, hypokalemic metabolic alkalosis, and hypercalciuria. Clinical disease results from defective renal reabsorption of sodium chloride in the thick ascending limb (TAL) of the Henle loop, where 30% of filtered salt is normally reabsorbed (Simon et al., 1997). Patients with antenatal forms of Bartter syndrome typically present with premature birth associated with polyhydramnios and low birth weight and may develop life-threatening dehydration in the neonatal period. Patients with classic Bartter syndrome (see BARTS3, 607364) present later in life and may be sporadically asymptomatic or mildly symptomatic (summary by Simon et al., 1996 and Fremont and Chan, 2012). For a discussion of genetic heterogeneity of Bartter syndrome, see 607364.

Paget disease is a metabolic bone disease characterized by focal abnormalities of increased bone turnover affecting one or more sites throughout the skeleton, primarily the axial skeleton. Bone lesions in this disorder show evidence of increased osteoclastic bone resorption and disorganized bone structure. See reviews by Ralston et al. (2008) and Ralston and Albagha (2014). For a discussion of genetic heterogeneity of Paget disease of bone, see 167250.

Infantile hypercalcemia is characterized by severe hypercalcemia, failure to thrive, vomiting, dehydration, and nephrocalcinosis. An epidemic of idiopathic infantile hypercalcemia occurred in the United Kingdom in the 1950s after the implementation of an increased prophylactic dose of vitamin D supplementation; however, the fact that most infants receiving the prophylaxis remained unaffected suggested that an intrinsic hypersensitivity to vitamin D might be implicated in the pathogenesis (summary by Schlingmann et al., 2011). Genetic Heterogeneity Infantile hypercalcemia-2 (HCINF2; 616963) is caused by mutation in the SLC34A1 gene (182309) on chromosome 5q35.

Infantile hypercalcemia is characterized by severe hypercalcemia with failure to thrive, vomiting, dehydration, and nephrocalcinosis (summary by Schlingmann et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of infantile hypercalcemia, see HCINF1 (143880).

Any familial isolated hyperparathyroidism in which the cause of the disease is a mutation in the GCM2 gene.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is characterized by: Ectopic calcifications (tumoral calcinosis) typically found in periarticular soft tissues exposed to repetitive trauma or prolonged pressure (e.g., hips, elbows, and shoulders); and Painful swellings (referred to as hyperostosis) in the areas overlying the diaphyses of the tibiae (and less often the ulna, metacarpal bones, and radius). The dental phenotype unique to HFTC includes enamel hypoplasia, short and bulbous roots, obliteration of pulp chambers and canals, and pulp stones. Less common are large and small vessel calcifications that are often asymptomatic incidental findings on radiologic studies but can also cause peripheral vascular insufficiency (e.g., pain, cold extremities, and decreased peripheral pulses). Less frequently reported findings include testicular microlithiasis and angioid streaks of the retina.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive metabolic disorder characterized by the progressive deposition of basic calcium phosphate crystals in periarticular spaces, soft tissues, and sometimes bone (Chefetz et al., 2005). The biochemical hallmark of tumoral calcinosis is hyperphosphatemia caused by increased renal absorption of phosphate due to loss-of-function mutations in the FGF23 (605380) or GALNT3 (601756) gene. The term 'hyperostosis-hyperphosphatemia syndrome' (HHS) is sometimes used when the disorder is characterized by involvement of the long bones associated with the radiographic findings of periosteal reaction and cortical hyperostosis. Although some have distinguished HHS from FTC by the presence of bone involvement and the absence of skin involvement (Frishberg et al., 2005), Ichikawa et al. (2010) concluded that the 2 entities represent a continuous spectrum of the same disease, best described as familial hyperphosphatemic tumoral calcinosis. HFTC is considered to be the clinical converse of autosomal dominant hypophosphatemic rickets (ADHR; 193100), an allelic disorder caused by gain-of-function mutations in the FGF23 gene and associated with hypophosphatemia and decreased renal phosphate absorption (Chefetz et al., 2005; Ichikawa et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of HFTC, see 211900.

Oculoskeletodental syndrome (OCSKD) is characterized by congenital cataract, short stature and various skeletal anomalies, dysmorphic facial features and dental anomalies, developmental delay, and stroke. Other recurrent features include hearing loss, secondary glaucoma, and nephrocalcinosis (Tiosano et al., 2019).