This is important, since in the early stages of RA, the synovium is primarily affected, and synovitis seems to be the best predictive marker of future joint damage. Blood tests
When RA is clinically suspected, a physician may test for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs measured as anti-CCP antibodies). It is positive in 75–85%, but a  negative RF or CCP antibody does not rule out RA, rather, the arthritis is called seronegative, which is in about 15–25% of people with RA. During the first year of illness, rheumatoid factor is more likely to be negative with some individuals becoming seropositive over time. RF is a non-specific antibody and seen in about 10% of healthy people, in many other chronic infections like hepatitis C, and chronic autoimmune diseases such as Sjögrens syndrome and systemic lupus erythematosus. Therefore, the test is not specific for RA.Hence, new serological tests check for anti-citrullinated protein antibodies ACPAs. These tests are again positive in 61–75% of all RA cases, but with a specificity of around 95%. As with RF, ACPAs are many times present before symptoms have started.The by far most common clinical test for ACPAs is the anti-cyclic citrullinated peptide (anti CCP) ELISA.
Cerebro-costo-mandibular syndrome is a very rare genetic disorder which is characterized by jaw/chin, palate and rib abnormalities. Signs and symptoms
The following list comprises the most common symptoms people with this disorder exhibit:
Severe micrognathia
Thorax in the shape of a bell
Cleft palate
Neonatal respiratory difficulties
Rib gapsCommon (but not the most) symptoms include:

External auditory canal atresia
Hearing loss
Failure to thrive
Glossoptosis
Intellectual disabilities
Fetal growth delays
Kyphosis
Short height
TracheomalaciaNot common but also not rare symptoms include:

Fifth finger clinodactyly
Cerebral calcification
Hydranencephaly
Meningocele
Microcephaly
Polycystic kidney dysplasia
Myelomeningocele
Porencephalic cyst
Short, hard palate
Spina bifida
Ventricular septal defect
Webbed neck

Causes
This disorder is caused by autosomal dominant mutations in the SNRPB gene, in chromosome 20. Epidemiology
Only 110 cases have been described in medical literature. == References ==