At right you see part of a Doppler ultrasound image from the left leg a 14-year-old girl with systemic lupus erythematosus (SLE). The pain in her leg had been worsening over the past week.
A month earlier, she presented with left knee arthritis and a vasculitic rash. The antinuclear antibody titer was positive.
She also has myositis, hypocomplementemia, leukopenia, and mild proteinuria.
She has responded to treatment with corticosteroids and hydroxychloroquine, and takes no other medications.
What does the image show? Can you guess the underlying condition that has caused it? (Give yourself extra credit for the correct answer; it's rare.)
Click here for the diagnosis and discussion.