Mixed Phenotype Acute Leukemia in Xeroderma Pigmentosum Patient with XPC Founder Mutation

Authors

• SG Khan
• MA Levoska
• D Tamura
• S Ito
• KR Calvo
• K Oetjen
• KH Kraemer
• JJ DiGiovanna

Abstract

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder characterized by skin as well as ocular abnormalities and increased risk of skin cancer, including melanoma. XP patients with defects in the nucleotide excision repair pathway genes (XP A - G) are hypersensitive to ultraviolet radiation from the sun. We describe a female XP-C patient (XP540BE, age 19 years) from Morocco with a homozygous two base (TG) deletion in exon 9 of the XPC gene (c1643_1644delTG, pVal548AlafsX25). Previously haplotype analysis revealed that this genetic change is a founder mutation which originated in the Mediterranean region approximately1,250 years ago. She developed her first skin cancer at age 8 years. She had > 40 skin cancers and 1 eye neoplasm. She had no menses for 1 year and her anti-mullerian hormone level was low consistent with early menopause seen in other XP-C patients. Prior to her visit, she had night sweats, shortness of breath climbing stairs, and lumps in her neck and groin. On examination at NIH, she had generalized lymphadenopathy, tachycardia and pancytopenia: WBC 1.75 K/μL, Hgb 6.8 g/dL, platelets 84 K/μL with 18.2% circulating blasts. Flow cytometry identified 3 distinct immature acute leukemic populations: B cell/myeloid blasts, T/B cell/myeloid blasts and T/B cell blasts confirming the diagnosis of a very rare mixed phenotype acute leukemia. We are in the process of analyzing the somatic mutations in the leukemia cells from patient. This study will highlight what distinct somatic mutations are present in the leukemia cells. These may provide information as to the origin of this unusual leukemia.

Scientific Focus Area: Genetics and Genomics

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