SS-A(Ro) is found in 60% to 70% of patients with
Sjögren's syndrome and 30% to 40% of patients with SLE. SS-B(La) is
found in 50% to 60% of Sjögren's syndrome and 10% to 15% of SLE. SS-A
cannot be demonstrated by immunofluorescence (it is soluble in the
buffers used), but SS-B may be seen as a speckled antinuclear pattern.
SS-A and SS-B are particularly useful in “ANA-negative” cases of SLE,
being present in a majority of such cases. Patients who are ANA-positive
and who have SS-A but not SS-B are very likely to have nephritis.
Antibodies to SS-A are also associated with HLA loci DR3 and DR2 and
with hereditary deficiency of C2. Anti-SS-A and anti-SS-B are found in
virtually all children with neonatal lupus. Patients with SS-A may also
have antibodies to cardiolipin, lupus anticoagulant, and clinical
thromboses. This has been termed antiphospholipid antibody syndrome.