A rare syndrome with most often right-sided clavicular pseudarthrosis.
Unknown. More than 200 cases have been reported worldwide.
Most likely autosomal dominant inheritance, although the majority of cases (approximately two-thirds) seem to occur sporadically. Mechanical factors during embryogenesis are most likely contributing to the pathogenesis.
Based on the clinical and radiographic findings.
Commonly, the disorder is characterized by a painless, prominent lump or spike under the skin causing some discomfort with activity. A possible combination with short stature, high-arched palate, and irregular upper teeth has been reported. Vascular thoracic outlet syndrome has been described in a small number of patients. Radiographs show a pseudarthrosis in the middle third of the clavicle, closer to the junction with the lateral third. The two segments are not in continuity, the ends are enlarged by bony hypertrophy and well-defined corticated borders, and no callus or reactive bone formation can be detected. The lesion manifests almost always on the right side (<10 left-sided cases have been reported, almost all of which were associated with dextrocardia and/or cervical ribs; in 10% the lesion occurs bilaterally), leading to speculations that extrinsic and excessive pressure exerted on the budding clavicle by the adjacent pulsatile subclavian artery, that normally runs at a more cranial level on the right, causes the pathology. Other researchers hypothesized that the anomaly results from failed coalescence of the two primary ossification centers of the clavicle. The differential diagnosis includes ☞Cleidocranial Dysostosis and posttraumatic pseudarthrosis (eg, form birth trauma; however, the absence of callus formation at the site of the pseudarthrosis and a history of uneventful delivery helps distinguishing it from the more common clavicular fracture with nonunion). Treatment remains controversial, being either conservative or surgical. Surgery can be indicated for upper limb dysfunction (eg, reduced strength or range of motion), prevention/treatment of thoracic outlet syndrome, or for cosmetic reasons due to significant chest asymmetry or skin irritations from the bony protuberance.
Precautions before anesthesia
Check for signs of thoracic outlet syndrome (compression of subclavian vein/artery and/or peripheral and sympathetic nerves) and exclude cardiac anomalies. The airway should be assessed for difficult management in the rare cases of associated (mild) facial dysmorphism.
Central venous access via the subclavian route on the affected side is best avoided because access may be distorted and therefore more challenging and associated with a higher risk for complications.
Other conditions to be considered
☞Cleidocranial Dysplasia (Cleidocranial Dysostosis; Scheuthauer-Marie-Sainton Syndrome; Marie-Sainton Syndrome): Generalized skeletal dysplasia resulting in defects in the development of skull, clavicles and pelvis, and dental abnormalities.
☞Craniofrontonasal Dysplasia (Frontofacionasal Dysostosis/Dysplasia): X-linked ...