MedGen

Fibrous dysplasia / McCune-Albright syndrome (FD/MAS), the result of an early embryonic postzygotic somatic activating pathogenic variant in GNAS (encoding the cAMP pathway-associated G-protein, Gsa), is characterized by involvement of the skin, skeleton, and certain endocrine organs. However, because Gsa signaling is ubiquitous, additional tissues may be affected. Café au lait skin macules are common and are usually the first manifestation of the disease, apparent at or shortly after birth. Fibrous dysplasia (FD), which can involve any part and combination of the craniofacial, axial, and/or appendicular skeleton, can range from an isolated, asymptomatic monostotic lesion discovered incidentally to severe disabling polyostotic disease involving practically the entire skeleton and leading to progressive scoliosis, facial deformity, and loss of mobility, vision, and/or hearing. Endocrinopathies include: Gonadotropin-independent precocious puberty resulting from recurrent ovarian cysts in girls and autonomous testosterone production in boys; Testicular lesions with or without associated gonadotropin-independent precocious puberty; Thyroid lesions with or without non-autoimmune hyperthyroidism; Growth hormone excess; FGF23-mediated phosphate wasting with or without hypophosphatemia in association with fibrous dysplasia; and Neonatal hypercortisolism. The prognosis for individuals with FD/MAS is based on disease location and severity. [from GeneReviews]

Spinocerebellar ataxia-27A (SCA27A) is an autosomal dominant neurologic disorder characterized by general cerebellar dysfunction manifest as gait disturbances, ataxia, tremor, dysarthria, and gaze-evoked nystagmus. The age at onset is highly variable: some patients present in infancy with nystagmus or delayed motor development, whereas others present as adults with tremor or gait difficulties. The disorder is slowly progressive, and ataxia may be very subtle or even absent. Cerebellar atrophy may or may not be observed on brain imaging. Individuals with SCA27A often show mild developmental delay with variably impaired intellectual development. Many patients report an exacerbation of symptoms with fever, emotional stress, or exercise, which can be reminiscent of episodic ataxia or be associated with outbursts, depression, or other behavioral and psychiatric disturbances. There is significant inter- and intrafamilial variability and patients show various combinations of neurologic features (summary by Tucker et al., 2013; Piarroux et al., 2020; Ceroni et al., 2023). For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400). [from OMIM]

WAC-related intellectual disability (ID) is typically characterized by variable degrees of developmental delay and/or intellectual disability. Behavioral abnormalities including anxiety, attention-deficit/hyperactivity disorder, and/or autism spectrum disorder are observed in the majority of older children and adults. Most affected infants have significant but nonspecific features at birth such as neonatal hypotonia and feeding problems. Some affected individuals come to medical attention with respiratory or vision problems. Facial features may be mildly dysmorphic, but are nonspecific. To date, 18 individuals have been identified with WAC-related ID. [from GeneReviews]

Dilated cardiomyopathy-2I (CMD2I) is characterized by early-onset severe congestive heart failure. Some patients experience supraventricular tachycardia. Structural heart defects and nemaline bodies in cardiac and skeletal muscle have been observed (Aspit et al., 2019; Cheema et al., 2020; Gurunathan et al., 2022). For a general phenotypic description and discussion of genetic heterogeneity of dilated cardiomyopathy, see 115200. [from OMIM]

Oculopharyngeal muscular dystrophy-2 (OPMD2) is an autosomal dominant muscle disorder characterized by early-onset ptosis, ophthalmoplegia, dysphagia, variable respiratory insufficiency, and proximal limb muscle weakness. Most patients have onset in the first years of life, although rare patients have onset in their teens. The disorder is slowly progressive and the severity is highly variable; the most severely affected individuals lose ambulation and may require tube-feeding or noninvasive ventilation (Kim et al., 2022). For a discussion of genetic heterogeneity of OPMD, see OPMD1 (164300). [from OMIM]

Birt-Hogg-Dube syndrome-2 (BHD2) is characterized by lipomatosis and fibrofolliculomas as well as renal cell carcinoma and other cancers (van de Beek et al., 2023). For a general phenotypic description and a discussion of genetic heterogeneity of BHD, see BHD1 (135150). [from OMIM]

ARCND2B is characterized by the typical features of auriculocondylar syndrome, including the pathognomonic question mark ears, consisting of a variable degree of clefting between the helix and earlobe, as well as hypoplasia of the mandibular condyle, temporomandibular joint abnormalities, micrognathia, microstomia, glossoptosis, and a round facial appearance with prominent cheeks. Patients have difficulty chewing, respiratory abnormalities, snoring, and obstructive and central apneas. In addition, they experience severe gastrointestinal problems, including feeding difficulties with failure to thrive, gastroesophageal reflux, and chronic constipation, and male patients show macropenis whereas female patients may exhibit clitoromegaly (summary by Leoni et al., 2016). Heterozygous mutation in the PLCB4 gene also causes an autosomal dominant form of auriculocondylar syndrome (see ARCND2A, 614669). For a discussion of genetic heterogeneity of auriculocondylar syndrome, see ARCND1 (602483). [from OMIM]

Auriculocondylar syndrome-4 (ARCND4) is characterized by malformed ears, round face, puffy cheeks, micrognathia, microstomia, malocclusion, and abnormal mandibular condyles with temporomandibular joint abnormalities. Patients may also experience conductive hearing loss (Masotti et al., 2008). For a general phenotypic description and a discussion of genetic heterogeneity of auriculocondylar syndrome, see ARCND1 (602483). [from OMIM]

Adult-onset dystonia-22 (DYT22AO) is an autosomal recessive disorder characterized by focal dystonia or tremor and mild cognitive impairment (Mencacci et al., 2021). [from OMIM]

Neurodevelopmental disorder with hypotonia and speech delay, with or without seizures (NEDHSS) is characterized by global developmental delay, impaired intellectual development with poor or absent speech, and fine and gross motor delay. Most affected individuals are severely affected and may be unable to walk, have feeding difficulties requiring tube-feeding, and develop early-onset seizures. Additional features may include cortical blindness and nonspecific structural brain abnormalities. Rare individuals present only with hypotonia and mild developmental delay (Paul et al., 2023). [from OMIM]

Congenital disorder of glycosylation type IIaa (CDG2AA) is an autosomal recessive disorder characterized by infantile mortality due to liver disease, skeletal abnormalities, and protein glycosylation defects (Linders et al., 2021). For an overview of congenital disorders of glycosylation, see CDG1A (212065) and CDG2A (212066). [from OMIM]

Juvenile-onset dystonia-22 (DYT22JO) is an autosomal recessive disorder characterized by progressive, generalized dystonia associated with cognitive decline and cerebellar atrophy on brain imaging (Mencacci et al., 2021). [from OMIM]

Amyotrophic lateral sclerosis-28 (ALS28) is an autosomal dominant neurodegenerative disorder characterized by adult onset of slowly progressive limb muscle weakness and atrophy resulting in gait difficulties, loss of ambulation, and distal upper limb weakness. Facial involvement is rare, but some patients may have respiratory insufficiency. EMG and muscle biopsy show active and chronic denervation. Patient-derived motor neurons show accumulation of TDP43 (605078) and toxic intranuclear RNA accumulation (Kume et al., 2023). For discussion of genetic heterogeneity of amyotrophic lateral sclerosis, see ALS1 (105400). [from OMIM]

Combined oxidative phosphorylation deficiency-58 (COXPD58) is an autosomal recessive disorder characterized by a wide range of clinical presentations including neonatal lactic acidosis, epileptic encephalopathy, developmental delay and impaired intellectual development with nonspecific changes on brain MRI, or mitochondrial myopathy with a treatable neuromuscular transmission defect (Van Haute et al., 2023). For a discussion of genetic heterogeneity of combined oxidative phosphorylation deficiency, see COXPD1 (609060). [from OMIM]

Autosomal dominant intellectual developmental disorder-73 (MRD73) is a highly variable neurodevelopmental disorder characterized by impaired intellectual development that ranges from mild to severe, speech delay, behavioral abnormalities, and nonspecific dysmorphic facial features (Janssen et al., 2022). [from OMIM]

Immunodeficiency-112 (IMD112) is an autosomal recessive primary immunologic disorder with variable manifestations beginning in early childhood. Some patients have recurrent bacterial, viral, and fungal infections, including disseminated bacillus Calmette-Guerin (BCG)-related infections, whereas at least 1 patient only presented with BCG-related infections. Immunologic workup shows variable abnormalities affecting lymphoid immunity, including hypogammaglobulinemia, lymphopenia or paradoxical lymphocytosis, and defects in B, T, and NK cell differentiation and function mainly due to disruption of the noncanonical NFKB (see 164011) signaling pathway (Willmann et al., 2014; Schlechter et al., 2017). [from OMIM]

Remitting megalencephalic leukoencephalopathy with subcortical cysts-4 (MLC4) is an autosomal recessive neurologic disorder characterized by macrocephaly in infancy associated with developmental delay, delayed walking, variable cognitive decline, behavioral abnormalities, and early-onset seizures. The severity of neurologic dysfunction is variable, even within a family, but tends to show improvement with time. Brain imaging shows swelling of the cerebral white matter and subcortical cysts in the anterior temporal region, consistent with MLC. Brain imaging abnormalities also tend to improve with time, indicating a remitting disease course (Passchier et al., 2023). For a discussion of genetic heterogeneity of megalencephalic leukoencephalopathy with subcortical cysts, see MLC1 (604004). [from OMIM]

Megalencephalic leukoencephalopathy with subcortical cysts-3 (MLC3) is a neurodegenerative disorder characterized by increased head circumference in infancy followed by progressive motor and cognitive decline in early childhood. Affected individuals either do not achieve walking or lose independent ambulation in the first or second decades. Cognitive impairment is variable and accompanied by poor speech and dysarthria. Most patients have early-onset seizures, which may be mild or refractory. Brain imaging shows unremitting megalencephalic leukoencephalopathy with subcortical cysts and swelling of the cerebral white matter (Passchier et al., 2023). For a discussion of genetic heterogeneity of megalencephalic leukoencephalopathy with subcortical cysts, see MLC1 (604004). [from OMIM]

Neurodevelopmental disorder with microcephaly and movement abnormalities (NEDMIM) is an autosomal recessive disorder characterized by global developmental delay, impaired intellectual development with poor or absent speech, and delayed walking with an abnormal gait. Affected individuals may show hypotonia or hypertonia with spasticity, ataxia, and choreoathetoid movements. Most patients have microcephaly and short stature. Ophthalmic features, behavioral abnormalities, and nonspecific dysmorphic features are commonly observed. Additional more variable features include seizures, brain imaging abnormalities, and skeletal defects (Serey-Gaut et al., 2023). [from OMIM]

Individuals with mutation in the PALB2 gene have an increased risk of developing breast or, to a lesser degree, ovarian cancer. In addition, PALB2 variants increase susceptibility to several other cancers, e.g., male breast cancer and pancreatic cancer (PNCA3; 613348) (Rahman et al., 2007; Norquist et al., 2018; Yang et al., 2020). For a discussion of genetic heterogeneity of breast-ovarian cancer susceptibility, see BROVCA1 (604370). For general discussions of breast cancer and ovarian cancer, see 114480 and 167000, respectively. Reviews Hamdan and Nowak (2023) reviewed the structure and function of the PALB2 gene, and its role in disease, including Fanconi anemia (FANCN; 610832), pancreatic cancer (PNCA3; 613348), and breast and ovarian cancer. [from OMIM]