Nodular and Diffuse Dermatitis

Abstract

There is a significant overlap with the nodular and diffuse pattern and the superficial and deep perivascular pattern; indeed, some entities discussed in Chap. 5 could arguably be included in this chapter as well (e.g., arthropod bite reaction). Other entities discussed in this chapter could also conceivably be discussed in the chapter on perivascular dermatitis (e.g., Sweet syndrome). The primary difference in the nodular and diffuse patterns from the perivascular pattern is that the inflammation is not just centered on vessels. On scanning magnification, nodular dermatitis is characterized by discrete areas of inflammation, separated by uninvolved areas. In contrast, the diffuse pattern demonstrates dense dermal inflammation without intervening areas of sparing. Distinction in individual cases is admittedly arbitrary and subject to individual interpretation. As with automobiles, your mileage may vary.