Congenital condition characterised by fusion of two or more vertebrae in the neck Klippel-Feil syndrome Other names Congenital dystrophia brevicollis, cervical vertebral fusion syndrome Woman with Klippel–Feil syndrome Pronunciation / ˌ k l ɪ . p ə l ˈ f aɪ l / Specialty Paediatrics , orthopaedics Symptoms Cervical spine fusion, scoliosis , spina bifida , heart defect , respiratory problems, other syndromic features Usual onset Congenital Causes Genetic mutations Risk factors Family history Prognosis Shorter life expectancy in some cases Frequency 1 in 40,000 to 42,000 births, females more affected than males Klippel–Feil syndrome ( KFS ), also known as cervical vertebral fusion syndrome , is a rare congenital condition characterized by the abnormal fusion of any two of the seven bones in the neck ( cervical vertebrae ). [1] : 578 It results in a limited ability to move the neck and shortness of the neck, resulting in the appearance of a low hairline . [2] The syndrome is difficult to diagnose, as it occurs in a group of patients affected with many different abnormalities who can only be unified by the presence of fused or segmental cervical vertebrae. [3] KFS is not always genetic and not always known the day of the birth. ... The most common signs of the disorder are restricted mobility of the neck and upper spine and a shortened neck with the appearance of a low hairline at the back of the head. [ citation needed ] Associated abnormalities may include: [6] [7] [8] [9] Scoliosis (sideways curvature of the spine) Spina bifida Problems with the kidneys and the ribs Cleft palate Dental problems (delayed dentition , cavities , missing teeth ) Respiratory problems Heart defects Short stature Duane syndrome Srb's anomaly Sprengel's deformity The disorder also may be associated with abnormalities of the head and face, skeleton , sex organs , muscles , brain and spinal cord , arms, legs and fingers. [ citation needed ] Genetics [ edit ] See also: Dominance (genetics) Mutations of the GDF6 , GDF3 and MEOX1 gene are associated with KFS. [2] The cause of the condition is unknown in individuals with KFS who do not have mutations of these two genes. ... They described patients who had a short, webbed neck ; decreased range of motion (ROM) in the cervical spine; and a low hairline. Feil subsequently classified the syndrome into 3 categories: [ citation needed ] Type I — Fusion of C2 and C3 with occipitalization of the atlas .