Mycosis fungoides (MF) is the most common variation of cutaneous T-cell lymphomas (CTCL). In patients with CTCL, itching can be a most important symptom but itching associated with MF is not relieved by conventional therapy using anti-histamines. The primary mechanisms of itching in MF patients is unclear.

An analysis was done to investigate the clinical and histopathological features associated with MF-related itching. Skin sections from MF patients and healthy subjects were used for pathophysiological analysis and for assessment of protease activity. The outcomes were compared with the degree of itching.

In the MF patients, 40% of patients did not report itching and 60% of them reported itching i.e. 40% moderate itching and 20% strong itching. The number of eosinophils that infiltrated into skin were increased in the group with strong itching. In the patients skin, both serine protease activity and immunoreactivity to kallikrein 5 (KLK5), which is a known itch mediator had increased the grade of itching.

The analysis results suggested that KLK5 and eosinophil infiltration might be involved in severity of itching in patients with MF.

Source: Shimizu K, Andoh T, Makino T, et al. Mechanisms of itching in mycosis fungoides: grade of itching correlates with eosinophil infiltration and kallikrein 5 expression.Eur J Dermatol. 2019 Jun 1; 29(3):268-273