Anti-C1q antibodies are associated with which of the following diseases?

Anti-C1q antibodies are most strongly associated with hypocomplementemic urticarial vasculitis syndrome (HUVS). This condition is characterized by low levels of complement (particularly C1q) and is associated with various symptoms, including urticarial lesions and arthralgia. The presence of these antibodies aids in the diagnosis of HUVS, as they specifically target components of the complement system, reflecting the underlying pathophysiology of the disease.

In contrast, while systemic lupus erythematosus (SLE) may also have complement involvement, its hallmark antibodies include anti-nuclear antibodies and specific antibodies like anti-double-stranded DNA. Rheumatoid arthritis predominantly involves different types of autoantibodies, including rheumatoid factor and anti-citrullinated protein antibodies, rather than anti-C1q. Granulomatosis with polyangiitis is primarily associated with anti-neutrophil cytoplasmic antibodies (ANCA), particularly anti-PR3 and anti-MPO, rather than antibodies against complement components such as C1q.

Thus, the association of anti-C1q antibodies with HUVS distinguishes it from other autoimmune diseases, making this the correct answer.