Experts Insights into Itch

During Dermatology Week 2022, Shawn Kwatra, MD, and Brian Kim, MD, MTR, FAAD, opened their discussion-based session, “Ask the Experts: Itch,” to offer insights on the pathophysiology of itch.

To start, Dr Kim asked what do physicians mean when they talk about itch? Dr Kwatra shared that he would say it is a conserved sensation that is very distinct from pain. The most common acute sensation is to scratch, which can be a challenge to address in chronic itch.

He also addressed how patients often get referred to dermatologists with scratch marks or skin picking because it is assumed they have itch. However, he argued that these might not be the truest indicators of itch sensation. He stated that physicians should be asking the following questions before assuming a patient has chronic itch:

• Is it more burning?
• Is there stinging?
• Are they experiencing pressure?

“One of the main problems with working up a chronic itch patient is you have so many different ideologies, so many different neural and immune and stromal factors that are responsible for it,” Dr Kwatra noted. “We need a way to classify and approach these patients so that we can go down one of infinite treatment pathways,” he added.

Another topic that was discussed was therapeutic agents, particularly how agents, such as dupilumab and nemolizumab, work. Dr Kwatra looked at it from a standpoint of prurigo nodularis, especially patients with type 2 inflammation. He noted that patients with prurigo nodularis have more IL-13 and IL-31 in the skin, in addition to an increased IL-4 receptor alpha. This seems to be a big cycle in terms of itch and scratch, and physicians have a variety of mechanisms, including agents that dull the immune and neural crosstalk for receptor alpha blockade.

Dr Kim agreed and added that these agents are likely to have anti-inflammatory properties because they block cytokines, especially at the neural interface for both atopic dermatitis and prurigo nodualris. He stated, “It doesn't mean [these agents are] doing necessarily exactly the same thing in both diseases. And depending on the disease, you may derive different kinds of benefits.”

The final topic Drs Kim and Kwatra addressed was the skepticism surrounding chronic pruritus of unknown origin despite clinics being filled with patients who have the disease. Dr Kwatra shared that the patient’s skin may present a few different types of presentations. These presentations vary and could include:

• Normal appearing skin
• Skin with some inducible erythema
• Varied involvement of some scattered redness or plaques
• Very strong features and types of inflammation

Dr Kwatra noted that “this is not a disease that was present. It happens out of the blue. The word immunosenescence is used because of the shifting to a T_H2 phenotype And so, I think, we need to have much greater awareness because I've seen so many patients referred who have that condition.”

He added that one of the main points of confusion for physicians is the fact that patients can also have neuropathic itch that may not respond to agents despite not having a rash, which makes it hard to look and see the difference.

“And currently we don't have any perfect way of knowing,” he concluded.

Reference
Kim B, Kwatra S. Ask the experts: itch. Presented at: Dermatology Week 2022; May 11-14, 2022; Virtual.