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Klippel-Feil syndrome (KFS) is a genetically heterogenous disorder characterized by variable degrees of bony fusion in the cervical vertebra. KFS patients may have spinal instability, disc degeneration, scoliosis, malformation of laryngeal cartilage with vocal impairment, cleft palate, facial dysmorphism, and limb and hand abnormalities. Sprengel anomaly and sensorineural, conductive or mixed hearing impairment are common.  The clinical triad of short neck, low posterior hairline and limited neck movement is observed in less than 50% of KFS patients. Klippel-Feil syndrome 1, autosomal dominant (KFS1; MIM 118100) is caused by mutations in the gene for growth differentiation factor 6 (GDF6), a member of the transforming growth factor-beta superfamily. Klippel-Feil syndrome 2, autosomal recessive (KFS2; MIM 214300) is caused by mutations in the gene for mesenchyme homeobox 1 (MEOX1). Klippel-Feil syndrome 3, autosomal dominant (KFS3; MIM 613702) is caused by mutations in the GDF3 gene, which codes for growth differentiation factor 3. Autosomal recessive mutations in the RIPPLY2 gene can also cause KFS (Klippel-Feil syndrome, RIPPLY2 related) and spondylocostal dysostosis 6 (SCDO6; MIM 616566), another vertebral malsegmentation disorder. Mutations in GDF6 also cause Leber congenital amaurosis 17 (LCA17; MIM 615360), microphthalmia, isolated 4 (MCOP4; MIM 613094) and microphthalmia, isolated, with coloboma 6 (MCOPCB6; MIM 613703). Mutations in GDF3 can also cause microphthalmia, isolated, with coloboma 6 (MCOPCB6; MIM 613703) and microphthalmia, isolated 7 (MCOP7; MIM 613704).