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Frontonasal dysostosis with delayed growth (short stature) and either severe mental retardation (Type I) or normal neurodevelopment (Type II). The anomalies mainly involve the facial midline, central nervous system, and multiple skeletal sites.
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Type I: Postaxial Polysyndactyly, Frontonasal Dysostosis, and Cleft Lip/Palate Syndrome; Cleft Lip/Palate with Frontonasal Dysostosis, and Postaxial Polysyndactyly.
Type II: Naguib-Richieri-Costa Syndrome; Richieri-Costa-Montagnoli Syndrome; Hypertelorism, Hypospadias, and Polysyndactyly Syndrome.
Dysostosis describes a defect in the ossification process, which results in either isolated or multiple malformations of individual bones. Axial involution of affected bones may occur. Dysostosis predominantly involves the extremities with the most common forms being syn- and polydactyly, which may occur in combination with craniofacial and other abnormalities.