July 2021 – Laboratory Genetics and Genomics Case 1

By MCL Education • July 9, 2021

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A 47-year-old man was referred to the genomics laboratory for alpha thalassemia testing because of microcytosis without anemia. Dosage analysis (PCR and Multiplex Ligation Probe Analysis) was used to detect deletion and duplication-type mutations and the Hb Constant Spring and alphaT Saudi point mutations within the alpha globin gene cluster. This method uses multiple probes that hybridize throughout the alpha-gene locus on chromosome 16 from the HS-40 regulatory region through the 3' hypervariable region.

What is this patient’s final result, and does this finding explain the patient’s phenotype?

• αα/αα; No, this result does not explain the patient’s phenotype.
• ααα(anti-4.2)/αα; Additional studies are required to determine if the abnormalities are in cis or trans in order to explain the patient’s phenotype.
• ααα(anti-4.2)/-3.7α; Additional studies are required to determine if the abnormalities are in cis or trans in order to explain the patient’s phenotype.
• -3.7α/αα; This likely explains the patient’s phenotype because carriers are known to experience microcytosis without anemia.

Alaa Koleilat, Ph.D.

Resident, Laboratory Genetics and Genomics
Mayo Clinic

Linda Hasadsri, M.D., Ph.D.

Consultant, Laboratory Genetics and Genomics
Mayo Clinic

Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

MCL Education

This post was developed by our Education and Technical Publications Team.