Transient neonatal hyperparathyroidism is characterized by interference with placental maternal-fetal calcium transport, causing fetal calcium deficiency resulting in hyperparathyroidism and metabolic bone disease. Because 80% of calcium is transferred during the third trimester, abnormalities may not be detected on second-trimester ultrasounds. Affected infants present at birth with prenatal fractures, shortened ribs, and bowing of long bones, as well as respiratory and feeding difficulties. Postnatal recovery or improvement is observed once calcium is provided orally, with most patients showing complete resolution of skeletal abnormalities by 2 years of age (Suzuki et al., 2018).

Syndrome that is characterized by communicating hydrocephalus, endocardial fibroelastosis and congenital cataracts. It has been described in two children, both of whom died a few months after birth (the first as a result of a respiratory infection and the second due to cardiac complications). The etiology of the syndrome is unknown but a viral or genetic origin has been proposed.

Congenital hydrocephalus-2 (HYC2) is a congenital disorder with onset in utero. Affected individuals have hydrocephalus with variably dilated ventricles and variable neurologic sequelae. Some individuals have other brain abnormalities, including lissencephaly, thinning of the corpus callosum, and neuronal heterotopia. Most patients have delayed motor development and some have delayed intellectual development and/or seizures. Additional congenital features, including cardiac septal defects, iris coloboma, and nonspecific dysmorphic features, may be observed. Some patients die in utero, in infancy, or in early childhood, whereas others have long-term survival (summary by Shaheen et al., 2017). For a discussion of genetic heterogeneity of congenital hydrocephalus, see 233600.

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A) is a autosomal recessive disorder associated with severe neurologic defects and resulting in early infantile death. The phenotype includes the alternative clinical designations Walker-Warburg syndrome (WWS) and muscle-eye-brain disease (MEB). The disorder represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as dystroglycanopathies (summary by Buysse et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670).

Sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD) is an autosomal recessive syndromic disorder characterized by onset of severe sideroblastic anemia in the neonatal period or infancy. Affected individuals show delayed psychomotor development with variable neurodegeneration. Recurrent periodic fevers without an infectious etiology occur throughout infancy and childhood; immunologic work-up shows B-cell lymphopenia and hypogammaglobulinemia. Other more variable features include sensorineural hearing loss, retinitis pigmentosa, nephrocalcinosis, and cardiomyopathy. Death in the first decade may occur (summary by Wiseman et al., 2013).

Macrocephaly, dysmorphic facies, and psychomotor retardation (MDFPMR) is an autosomal recessive neurodevelopmental disorder characterized by large head and somatic overgrowth apparent at birth followed by global developmental delay. Affected individuals have characteristic dysmorphic facial features and persistently large head, but increased birth weight normalizes with age. Additional neurologic features, including seizures, hypotonia, and gait ataxia, may also occur. Patients show severe intellectual impairment (summary by Ortega-Recalde et al., 2015).

Cole-Carpenter syndrome is characterized by bone fragility, craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features (Cole and Carpenter, 1987). Genetic Heterogeneity of Cole-Carpenter Syndrome Cole-Carpenter syndrome-2 (CLCRP2; 616294) is caused by mutation in the SEC24D gene (607186).

Primary ciliary dyskinesia is a genetically heterogeneous autosomal recessive disorder resulting from loss of function of different parts of the primary ciliary apparatus, most often dynein arms. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus (270100), and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003). Genetic Heterogeneity of Primary Ciliary Dyskinesia Other forms of primary ciliary dyskinesia include CILD2 (606763), caused by mutation in the DNAAF3 gene (614566) on 19q13; CILD3 (608644), caused by mutation in the DNAH5 gene (603335) on 5p15; CILD4 (608646), mapped to 15q13; CILD5 (608647), caused by mutation in the HYDIN gene (610812) on 16q22; CILD6 (610852), caused by mutation in the TXNDC3 gene (607421) on 7p14; CILD7 (611884), caused by mutation in the DNAH11 gene (603339) on 7p15; CILD8 (612274), mapped to 15q24-q25; CILD9 (612444), caused by mutation in the DNAI2 gene (605483) on 17q25; CILD10 (612518), caused by mutation in the DNAAF2 gene (612517) on 14q21; CILD11 (612649), caused by mutation in the RSPH4A gene (612647) on 6q22; CILD12 (612650), caused by mutation in the RSPH9 gene (612648) on 6p21; CILD13 (613193), caused by mutation in the DNAAF1 gene (613190) on 16q24; CILD14 (613807), caused by mutation in the CCDC39 gene (613798) gene on 3q26; CILD15 (613808), caused by mutation in the CCDC40 gene (613799) on 17q25; CILD16 (614017), caused by mutation in the DNAL1 gene (610062) on 14q24; CILD17 (614679), caused by mutation in the CCDC103 gene (614677) on 17q21; CILD18 (614874), caused by mutation in the DNAAF5 gene (614864) on 7p22; CILD19 (614935), caused by mutation in the LRRC6 gene (614930) on 8q24; CILD20 (615067), caused by mutation in the CCDC114 gene (615038) on 19q13; CILD21 (615294), caused by mutation in the DRC1 gene (615288) on 2p23; CILD22 (615444), caused by mutation in the ZMYND10 gene (607070) on 3p21; CILD23 (615451), caused by mutation in the ARMC4 gene (615408) on 10p; CILD24 (615481), caused by mutation in the RSPH1 gene (609314) on 21q22; CILD25 (615482), caused by mutation in the DYX1C1 gene (608706) on 15q21; CILD26 (615500), caused by mutation in the C21ORF59 gene (615494) on 21q22; CILD27 (615504), caused by mutation in the CCDC65 gene (611088) on 12q13; CILD28 (615505), caused by mutation in the SPAG1 gene (603395) on 8q22; CILD29 (615872), caused by mutation in the CCNO gene (607752) on 5q11; CILD30 (616037), caused by mutation in the CCDC151 gene (615956) on 19p13; CILD32 (616481), caused by mutation in the RSPH3 gene (615876) on 6q25; CILD33 (616726), caused by mutation in the GAS8 gene (605178) on 16q24; CILD34 (617091), caused by mutation in the DNAJB13 gene (610263) on 11q13; CILD35 (617092), caused by mutation in the TTC25 gene (617095) on 17q21; CILD36 (300991), caused by mutation in the PIH1D3 gene (300933) on Xq22; CILD37 (617577), caused by mutation in the DNAH1 gene (603332) on 3p21; CILD38 (618063), caused by mutation in the CFAP300 gene (618058) on 11q22; CILD39 (618254), caused by mutation in the LRRC56 gene (618227) on 11p15; CILD40 (618300), caused by mutation in the DNAH9 gene (603330) on 17p12; CILD41 (618449), caused by mutation in the GAS2L2 gene (611398) on 17q12; CILD42 (618695), caused by mutation in the MCIDAS gene (614086) on 5q11; CILD43 (618699), caused by mutation in the FOXJ1 gene (602291) on 17q25; CILD44 (618781), caused by mutation in the NEK10 gene (618726) on 3p24; CILD45 (618801), caused by mutation in the TTC12 gene (610732) on 11q23; CILD46 (619436), caused by mutation in the STK36 gene (607652) on 2q35; CILD47 (619466), caused by mutation in the TP73 gene (601990) on 1p36; CILD48 (620032), caused by mutation in the NME5 gene (603575) on chromosome 5q31; CILD49 (620197), caused by mutation in the CFAP74 gene (620187) on chromosome 1p36; CILD50 (620356), caused by mutation in the DNAH7 gene (610061) on chromosome 2q32; CILD51 (620438), caused by mutation in the BRWD1 gene (617824) on chromosome 21q22; CILD52 (620570), caused by mutation in the DAW1 gene (620279) on chromosome 2q36; and CILD53 (620642), caused by mutation in the CLXN gene (619564) on chromosome 8q11. Ciliary abnormalities have also been reported in association with both X-linked and autosomal forms of retinitis pigmentosa. Mutations in the RPGR gene (312610), which underlie X-linked retinitis pigmentosa (RP3; 300029), are in some instances (e.g., 312610.0016) associated with recurrent respiratory infections indistinguishable from immotile cilia syndrome; see 300455. Afzelius (1979) gave an extensive review of cilia and their disorders. There are also several possibly distinct CILDs described based on the electron microscopic appearance of abnormal cilia, including CILD with transposition of the microtubules (215520), CILD with excessively long cilia (242680), and CILD with defective radial spokes (242670).

Chilton-Okur-Chung neurodevelopmental syndrome (CHOCNS) is characterized mainly by global developmental delay with variably impaired intellectual development and occasional speech delay. Most patients have behavioral abnormalities, including autism spectrum disorder, ADHD, and aggression. About half of patients have dysmorphic facial features, and about half have nonspecific brain abnormalities, including thin corpus callosum. Rare involvement of other organ systems may be present. At least 1 child with normal development at age 2.5 years has been reported (Chilton et al., 2020).