A Case of Two Young Brothers with Natural-Killer/T-Cell Lymphoma
Authors: Tang Tiffany , Nairismagi Maarja-Liisa , Ng Alvin Yu Jin , Venkatesh Byrappa , Ngeow Joanne , Li Shao-Tzu , Laurensia Yurike , Lim Jing Quan , Nagarajan Sanjanaa , Chia Burton , Tan Jing , Goh Yeow Tee , Tao Miriam , Quek Richard Hong Hui , Farid Mohamad , Lim Soon Thye , Ong Choon Kiat 
Published: October 2019

Abstract
Introduction:
Natural-killer/T-cell lymphoma (NKTL) is a rare subset of non-Hodgkin's lymphoma that is more prevalent in Asia than in the West. We report a case of two brothers who were diagnosed with NKTL and died of their disease at 23 and 37 years old respectively, and further investigations performed to determine the underlying genetic basis to their disease.
Methods
Both patients were recruited into the Singapore lymphoma study where retrieval of their clinical data and biospecimens had been approved by the Singhealth instititutional review board. Their clinical courses are described using information from electronic medical records.
For the older brother we extracted tumor DNA from a patient-derived xenograft (PDX), and DNA from a buccal swab and peripheral blood (PB) sample. In the younger brother DNA was extracted from normal and tumor tissue from archived formalin fixed paraffin embedded (FFPE) samples. DNA from the unaffected mother, older brother and paternal aunt were obtained from PB and buccal swab samples. We performed whole exome sequencing (WES) on the younger affected brother's tumor, the older affected brother's, mother's and unaffected brother's blood sample. Subsequent analysis of variants took into account autosomal recessive (AR), X-linked recessive (XR) and autosomal dominant (AD) inheritance models. Candidate genes are validated using Sanger sequencing. Microarray on the older affected brother and 12 sporadic NKTL cases were analyzed.
Results
The older affected brother was 35 years old when he presented with left nasal blockage in March 2013. He was diagnosed with stage IIA NKTL and treated with 4 cycles of bortezomib-GIFOX as part of a clinical trial followed by radiotherapy to the nasal region. He had primary refractory disease and was further treated with 4 cycles of SMILE followed by high dose chemotherapy and autologous stem cell transplantation (HDC/ASCT). He progressed and received off-label ruxolitinib, and everolimus/HDAC inhibitor as part of a clinical trial. He then had radiotherapy to an ulcerating penile lesion before he died of progressive disease 27months after diagnosis. The younger affected brother was 18 years old when he was diagnosed with NKTL in 1998. He received 6 cycles of CHOP with intravenous high-dose methotrexate and intrathecal methotrexate and went into remission. Three years later, he was diagnosed with chronic myeloid leukemia and 6 years later, he had a relapse of NKTL for which he received ESHAP, TBI and allogeneic bone marrow transplant. He died of transplant related complication 6 years after diagnosis. They both have an older unaffected brother. Their father died of non-malignant condition in his fifties and their mother remains well. They have no other relatives with hematologic malignancy.
We have identified several candidate variants and genes on WES that are being validated and functional studies are ongoing. GEP shows 234 genes that are significantly upregulated in the affected brother's tumor compared to 12 sporadic NKTL tumors including p53 and 12 genes that were significantly downregulated including CTLA4 and virus entry pathways.
Conclusion:
We describe a case of two brothers with a rare lymphoma and the ongoing efforts in elucidating the genetic basis of their disease. To the best of our knowledge this is the first study of its kind to be presented.

Disclosures
No relevant conflicts of interest to declare.