Hajdu Cheney Syndrome (HCS) is a rare disease characterized by acroosteolysis, severe osteoporosis, short stature, specific craniofacial features, wormian bones, neurological symptoms, cardiovascular defects, and polycystic kidneys.
Cheney Syndrome; Arthrodentoosteodysplasia; Osteopathia Dysplastica Familiaris; Familial Osteodysplasia; Cranio-skeletal Dysplasia with Acroosteolysis.
First described by N. Hajdu and R. Kauntze in 1948 and later by W.D. Cheney in 1965.
Approximately 60 cases have been described.
Autosomal dominant. Sporadic cases apparently represent new mutations. HCS is associated with mutations in exon 34 of NOTCH2 upstream the PEST domain that lead to the creation of a truncated and stable NOTCH2 protein with enhanced NOTCH2 signaling activity.
Unknown. The disorder probably results from defective development of bone rather than destruction of bone already formed.
Based on the clinical findings of short stature, hand pain, weakness, pathologic fractures, and distal osteolytic lesions.
The clinical phenotype is variable, and none of the patients have all the signs mentioned in the following description. At birth, many of these patients look normal or only show mild and unspecific dysmorphic signs, such as downslanted palpebral fissures, flat and broad nasal bridge, long philtrum, low-set ears, or hypertelorism. However, the facial appearance changes over time, that is, they become coarser, not starting before early or middle childhood. The diagnosis may be delayed until the patient is in the second or even third decade, when they typically present with swelling and pain of the fingers. The clinical features of this disorder may involve: head and neck (normal intelligence, although mild developmental delay has been described in some cases), progressive hearing loss (one-third of patients), speech abnormalities, bathrocephaly (a form of posterior sagittal synostosis), platybasia (basilar invagination, a developmental deformity resulting from seemingly upward pushing of the cervical spine and consecutive bulging of the occipital bone), multiple wormian bones, enlarged pituitary fossa without endocrine abnormalities, open cranial sutures, absent or hypoplastic frontal sinuses, low-set ears, midfacial flattening, micrognathia or retrognathia (>50% of patients), cleft lip, high-arched or cleft palate, early loss of teeth, hypertelorism, limited neck movement, and the musculoskeletal system (with short stature in >50% of patients), generalized osteoporosis predisposing to multiple fractures, terminal phalangeal acroosteolysis, cervical spine instability, vertebral anomalies (collapsed “fishbone” vertebrae), kyphosis, scoliosis, and joint hyperextensibility and dislocations. Other features are associated with the respiratory system (upper airway obstruction, vocal cord paralysis, deep voice), the nervous system (☞Arnold Chiari Malformation, hydrocephalus and cranial nerve damage [both possibly caused by platybasia], mental retardation, sensory changes such as pain and paresthesias may accompany the acroosteolytic lesions), the cardiovascular system (atrial and ventricular septal defects, patent ductus ...