TY - JOUR
T1 - Whole-exome sequencing identifies an α-globin cluster triplication resulting in increased clinical severity of β-thalassemia
AU - Steinberg-Shemer, Orna
AU - Ulirsch, Jacob C.
AU - Noy-Lotan, Sharon
AU - Krasnov, Tanya
AU - Attias, Dina
AU - Dgany, Orly
AU - Laor, Ruth
AU - Sankaran, Vijay G.
AU - Tamary, Hannah
N1 - Publisher Copyright:
© 2017 Steinberg-Shemer et al.; Published by Cold Spring Harbor Laboratory Press.
PY - 2017/11/1
Y1 - 2017/11/1
N2 - Whole-exome sequencing (WES) has been increasingly useful for the diagnosis of patients with rare causes of anemia, particularly when there is an atypical clinical presentation or targeted genotyping approaches are inconclusive. Here, we describe a 20-yr-old man with a lifelong moderate-to-severe anemia with accompanying splenomegaly who lacked a definitive diagnosis. After a thorough clinical workup and targeted genetic sequencing, we identified a paternally inherited β-globin mutation (HBB:c.93-21G>A, IVS-I-110:G>A), a known cause of β-thalassemia minor. As this mutation alone was inconsistent with the severity of the anemia, we performed WES. Although we could not identify any relevant pathogenic single-nucleotide variants (SNVs) or small indels, copy-number variant (CNV) analyses revealed a likely triplication of the entire α-globin cluster, which was subsequently confirmed by multiplex ligation-dependent probe amplification. Treatment and follow-up was redefined according to the diagnosis of β-thalassemia intermedia resulting from a single β-thalassemia mutation in combination with an α-globin cluster triplication. Thus, we describe a case where the typical WES-based analysis of SNVs and small indels was unrevealing, but WES-based CNV analysis resulted in a definitive diagnosis that informed clinical decision-making. More generally, this case illustrates the value of performing CNV analysis when WES is otherwise unable to elucidate a clear genetic diagnosis.
AB - Whole-exome sequencing (WES) has been increasingly useful for the diagnosis of patients with rare causes of anemia, particularly when there is an atypical clinical presentation or targeted genotyping approaches are inconclusive. Here, we describe a 20-yr-old man with a lifelong moderate-to-severe anemia with accompanying splenomegaly who lacked a definitive diagnosis. After a thorough clinical workup and targeted genetic sequencing, we identified a paternally inherited β-globin mutation (HBB:c.93-21G>A, IVS-I-110:G>A), a known cause of β-thalassemia minor. As this mutation alone was inconsistent with the severity of the anemia, we performed WES. Although we could not identify any relevant pathogenic single-nucleotide variants (SNVs) or small indels, copy-number variant (CNV) analyses revealed a likely triplication of the entire α-globin cluster, which was subsequently confirmed by multiplex ligation-dependent probe amplification. Treatment and follow-up was redefined according to the diagnosis of β-thalassemia intermedia resulting from a single β-thalassemia mutation in combination with an α-globin cluster triplication. Thus, we describe a case where the typical WES-based analysis of SNVs and small indels was unrevealing, but WES-based CNV analysis resulted in a definitive diagnosis that informed clinical decision-making. More generally, this case illustrates the value of performing CNV analysis when WES is otherwise unable to elucidate a clear genetic diagnosis.
KW - hypochromic microcytic anemia
KW - reduced beta/alpha synthesis ratio
UR - http://www.scopus.com/inward/record.url?scp=85039799217&partnerID=8YFLogxK
U2 - 10.1101/mcs.a001941
DO - 10.1101/mcs.a001941
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C2 - 28667000
AN - SCOPUS:85039799217
SN - 2373-2873
VL - 3
JO - Cold Spring Harbor molecular case studies
JF - Cold Spring Harbor molecular case studies
IS - 6
ER -