American Board of Internal Medicine (ABIM) Certification Practice Exam

What condition should be considered for patients with multisystem vasculitic disease if C4 levels are low and rheumatoid factor is present?

1. Systemic lupus erythematosus

2. Cryoglobulinemia

3. Granulomatosis with polyangiitis

4. Antiphospholipid syndrome

The correct answer is: Cryoglobulinemia

In patients presenting with multisystem vasculitic disease, low levels of complement component C4, along with the presence of rheumatoid factor, suggest the possibility of cryoglobulinemia. This condition is characterized by the presence of abnormal proteins in the blood (cryoglobulins) that can precipitate under low temperatures, leading to inflammation and damage to small and medium-sized blood vessels. Cryoglobulinemia is often associated with conditions that lead to chronic infection or immune complex deposition, particularly viral infections like hepatitis C, but it can also be seen in other autoimmune diseases. The reduction in complement levels occurs due to consumption as the immune complex-mediated inflammation activates the complement cascade. The presence of rheumatoid factor further indicates an autoimmune process, which complements the association with cryoglobulinemia, especially when considering a backdrop of systemic inflammation and vasculopathy. The other conditions listed can present with various immune markers and levels of complement components, but they do not fit as neatly with the specific lab findings of low C4 levels and the presence of rheumatoid factor as cryoglobulinemia does. For instance, systemic lupus erythematosus could also present with low complement levels and rheumatoid factor, but the specific combination here points more decisively towards cryoglob