Cleidocranial dysplasia (CCD) spectrum disorder is a skeletal dysplasia that represents a clinical continuum ranging from classic CCD (triad of delayed closure of the cranial sutures, hypoplastic or aplastic clavicles, and dental abnormalities) to mild CCD to isolated dental anomalies without the skeletal features. Most individuals come to diagnosis because they have classic features. At birth, affected individuals typically have abnormally large, wide-open fontanelles that may remain open throughout life. Clavicular hypoplasia can result in narrow, sloping shoulders that can be opposed at the midline. Moderate short stature may be observed, with most affected individuals being shorter than their unaffected sibs. Dental anomalies may include supernumerary teeth, eruption failure of the permanent teeth, and presence of the second permanent molar with the primary dentition. Individuals with CCD spectrum disorder are at increased risk of developing recurrent sinus infections, recurrent ear infections leading to conductive hearing loss, and upper-airway obstruction. Intelligence is typically normal.

Pycnodysostosis is characterized by short-limbed short stature, typical facial appearance (convex nasal ridge and small jaw with obtuse mandibular angle), osteosclerosis with increased bone fragility, acroosteolysis of the distal phalanges, delayed closure of the cranial sutures, and dysplasia of the clavicle. In affected individuals, the facial features become more prominent with age, likely due to progressive acroosteolysis of the facial bones, but can usually be appreciated from early childhood, particularly the small jaw and convex nasal ridge. Additional features include dental and nail anomalies. Intelligence is typically normal with mild psychomotor difficulties reported in some individuals.

Marshall syndrome (MRSHS) is characterized by midfacial hypoplasia, cleft palate, ocular anomalies including high myopia and cataracts, sensorineural hearing loss, short stature with spondyloepiphyseal dysplasia, and arthropathy. In contrast to Stickler syndrome type II, it has less severe eye findings but striking ocular hypertelorism, more pronounced maxillary hypoplasia, and ectodermal abnormalities (summary by Shanske et al., 1997 and Ala-Kokko and Shanske, 2009).

The X-linked otopalatodigital (X-OPD) spectrum disorders, characterized primarily by skeletal dysplasia, include the following: Otopalatodigital syndrome type 1 (OPD1). Otopalatodigital syndrome type 2 (OPD2). Frontometaphyseal dysplasia type 1 (FMD1). Melnick-Needles syndrome (MNS). Terminal osseous dysplasia with pigmentary skin defects (TODPD). In OPD1, most manifestations are present at birth; females can present with severity similar to affected males, although some have only mild manifestations. In OPD2, females are less severely affected than related affected males. Most males with OPD2 die during the first year of life, usually from thoracic hypoplasia resulting in pulmonary insufficiency. Males who live beyond the first year of life are usually developmentally delayed and require respiratory support and assistance with feeding. In FMD1, females are less severely affected than related affected males. Males do not experience a progressive skeletal dysplasia but may have joint contractures and hand and foot malformations. Progressive scoliosis is observed in both affected males and females. In MNS, wide phenotypic variability is observed; some individuals are diagnosed in adulthood, while others require respiratory support and have reduced longevity. MNS in males results in perinatal lethality in all recorded cases. TODPD, seen only in females, is characterized by a skeletal dysplasia that is most prominent in the digits, pigmentary defects of the skin, and recurrent digital fibromata.

A rare genetic primary bone dysplasia disease characterized by progressive osteosclerosis and platyspondyly.

Mulibrey nanism (MUL) is a rare autosomal recessive growth disorder with prenatal onset, including occasional progressive cardiomyopathy, characteristic facial features, failure of sexual maturation, insulin resistance with type 2 diabetes, and an increased risk for Wilms tumor (summary by Hamalainen et al., 2006).

Hajdu-Cheney syndrome (HJCYS) is a rare autosomal dominant skeletal disorder characterized by short stature, coarse and dysmorphic facies, bowing of the long bones, and vertebral anomalies. Facial features include hypertelorism, bushy eyebrows, micrognathia, small mouth with dental anomalies, low-set ears, and short neck. There is progressive focal bone destruction, including acroosteolysis and generalized osteoporosis. Additional and variable features include hearing loss, renal cysts, and cardiovascular anomalies (summary by Ramos et al., 1998; Simpson et al., 2011; Isidor et al., 2011).

A rare developmental defect during embryogenesis syndrome characterized by the association of microcornea, glaucoma and frontal sinus hypoplasia. Thick palmar skin and torus palatinus have also been reported. There have been no further descriptions in the literature since 1995.

Alpha-thalassemia X-linked intellectual disability (ATR-X) syndrome is characterized by distinctive craniofacial features, genital anomalies, hypotonia, and mild-to-profound developmental delay / intellectual disability (DD/ID). Craniofacial abnormalities include small head circumference, telecanthus or widely spaced eyes, short triangular nose, tented upper lip, and thick or everted lower lip with coarsening of the facial features over time. While all affected individuals have a normal 46,XY karyotype, genital anomalies comprise a range from hypospadias and undescended testicles, to severe hypospadias and ambiguous genitalia, to normal-appearing female external genitalia. Alpha-thalassemia, observed in about 75% of affected individuals, is mild and typically does not require treatment. Osteosarcoma has been reported in a few males with germline pathogenic variants.

The X-linked otopalatodigital (X-OPD) spectrum disorders, characterized primarily by skeletal dysplasia, include the following: Otopalatodigital syndrome type 1 (OPD1). Otopalatodigital syndrome type 2 (OPD2). Frontometaphyseal dysplasia type 1 (FMD1). Melnick-Needles syndrome (MNS). Terminal osseous dysplasia with pigmentary skin defects (TODPD). In OPD1, most manifestations are present at birth; females can present with severity similar to affected males, although some have only mild manifestations. In OPD2, females are less severely affected than related affected males. Most males with OPD2 die during the first year of life, usually from thoracic hypoplasia resulting in pulmonary insufficiency. Males who live beyond the first year of life are usually developmentally delayed and require respiratory support and assistance with feeding. In FMD1, females are less severely affected than related affected males. Males do not experience a progressive skeletal dysplasia but may have joint contractures and hand and foot malformations. Progressive scoliosis is observed in both affected males and females. In MNS, wide phenotypic variability is observed; some individuals are diagnosed in adulthood, while others require respiratory support and have reduced longevity. MNS in males results in perinatal lethality in all recorded cases. TODPD, seen only in females, is characterized by a skeletal dysplasia that is most prominent in the digits, pigmentary defects of the skin, and recurrent digital fibromata.

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).