INTRODUCTION
Immune checkpoints are inhibitory pathways within the immune system that maintain self-tolerance and regulate the duration and strength of immune responses.1 Tumors can exploit this mechanism to evade immune surveillance by upregulating the expression of checkpoint molecules, downregulating major histocompatibility complex (MHC) molecules, producing immunosuppressive factors, and altering the tumor microenvironment.1
To combat this mechanism, immunotherapy with immune checkpoint inhibitors (ICIs) has emerged as a revolutionary therapy for cancers such as metastatic malignant melanoma, non-small cell lung cancer, and urethral carcinoma.5 ICIs work by blocking the interaction between checkpoint proteins with their partner proteins, thereby suppressing the inhibitory signaling and allowing the T cells to recognize and attack cancer cells.6
Currently, the most widely used ICIs target the programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) receptors.6 PD-1 inhibitors bind to the receptor on T cells to block the PD-1/PD-L1 immune-suppressing interaction.7,8 Examples of these agents include pembrolizumab, nivolumab, and cemiplimab. PD-L1 inhibitors target the ligand portion of the PD-1/PD-L1 interaction and include agents such as atezolizumab, avelumab, and durvalumab.7,8 CTLA-4 inhibitors such as ipilimumab indirectly regulate CD28/B7 interaction to promote T-cell activation.9,10
Despite their therapeutic impact, ICIs are not without limitations. Many studies have shown irAEs due to their modulation of the immune system. These irAEs include skin rash, hypothyroidism, and GI toxicity.2,11,12 Recently, alopecia has been reported as a rare side effect in patients, however, details to guide patients while on therapy are lacking.3 The evidence concerning the causal relationship between ICI therapy and alopecia is limited, necessitating further studies to better understand this potential adverse effect. Given the significant physiological stress alopecia can cause, early diagnosis and timely treatment are crucial.13 Here, we aim to summarize the data on alopecia, both non-scarring and scarring, following ICI therapy, to gain insights into onset, prognosis, and potential treatments.
To combat this mechanism, immunotherapy with immune checkpoint inhibitors (ICIs) has emerged as a revolutionary therapy for cancers such as metastatic malignant melanoma, non-small cell lung cancer, and urethral carcinoma.5 ICIs work by blocking the interaction between checkpoint proteins with their partner proteins, thereby suppressing the inhibitory signaling and allowing the T cells to recognize and attack cancer cells.6
Currently, the most widely used ICIs target the programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) receptors.6 PD-1 inhibitors bind to the receptor on T cells to block the PD-1/PD-L1 immune-suppressing interaction.7,8 Examples of these agents include pembrolizumab, nivolumab, and cemiplimab. PD-L1 inhibitors target the ligand portion of the PD-1/PD-L1 interaction and include agents such as atezolizumab, avelumab, and durvalumab.7,8 CTLA-4 inhibitors such as ipilimumab indirectly regulate CD28/B7 interaction to promote T-cell activation.9,10
Despite their therapeutic impact, ICIs are not without limitations. Many studies have shown irAEs due to their modulation of the immune system. These irAEs include skin rash, hypothyroidism, and GI toxicity.2,11,12 Recently, alopecia has been reported as a rare side effect in patients, however, details to guide patients while on therapy are lacking.3 The evidence concerning the causal relationship between ICI therapy and alopecia is limited, necessitating further studies to better understand this potential adverse effect. Given the significant physiological stress alopecia can cause, early diagnosis and timely treatment are crucial.13 Here, we aim to summarize the data on alopecia, both non-scarring and scarring, following ICI therapy, to gain insights into onset, prognosis, and potential treatments.
