Significant response to Pembrolizumab for metastatic cutaneous squamous cell carcinoma in patient with Netherton syndrome.

Background: Netherton syndrome is a rare autosomal recessive disease that presents with a triad of symptoms which include atopic diathesis, ichthyosis linearis circumflexa, and hair shaft abnormality termed "Bamboo Hair". Netherton syndrome patients can develop cutaneous squamous cell carcinoma (cSCC) in unusually young age. Pembrolizumab is the first line treatment for locally advanced and recurrent/metastatic cSCC. Case presentation: A 44-year-old man with a history of Netherton syndrome and multiple skin squamous cell carcinoma was diagnosed with locally advanced and recurrent/metastatic cSCC two years ago. He was started on Pembrolizumab as a treatment for his cSCC. The immunotherapy course was well tolerated with no significant side effects including the expected immune related adverse events seen in patients treated with this medication. PET/CT scan showed significant regression of his disease consistent with partial response according to the response evaluation criteria in solid tumors. Discussion: Incurable and recurrent cSCC tends to metastasize, leading to an extremely poor long-term prognosis, and the treatment options for locally advanced or metastatic disease are few. Pembrolizumab, an immune checkpoint inhibitors (ICIs) showed a benefit in patients with various tumors including squamous cell carcinoma, but using this drug which is working by enhancing the immunity against tumor in patient with altered immunity like Netherton syndrome was a bit of a challenge, in terms of both effectiveness and safety. Conclusion: Pembrolizumab had a effective and safe treatment profile when it was used as a monotherapy for treating a Netherton syndrome patient diagnosed with locally advanced and recurrent/metastatic cSCC.