ISSN 2997-1036
International Journal of Hematology | Vol. 10, No. 4, April 2019 | pp. 25–32
DOI: 10.46882/2019/IJH/000112
Original Article
Title: Prevalence and molecular characteristics of CALR exon 9 Type 1 and Type 2 variants in essential thrombocythemia
Names of Authors: G. M. Babalola¹, I. N. Nwosu², K. S. Abubakar³
Authors’ Affiliations: ¹Department of Haematology and Blood Transfusion, Lagos University Teaching Hospital, Lagos, Nigeria; ²Department of Medicine, University of Nigeria, Nsukka, Nigeria; ³Department of Pathology, Bayero University, Kano, Nigeria
Abstract: Identifying specific calreticulin (CALR) mutation sub-types helps refine clinical risk evaluation in Janus kinase 2 (JAK2)-negative myeloproliferative malignancies. This cross-sectional study investigated the prevalence, hematological profiles, and thromboembolic rates linked to CALR exon 9 Type 1 (52-bp deletion) and Type 2 (5-bp insertion) variants in 54 adult patients diagnosed with essential thrombocythemia. Genomic DNA was isolated from peripheral blood leucocytes, followed by fragment analysis and direct Sanger sequencing. CALR mutations were detected in 33.3% (18 of 54) of the patients. Type 1 deletion variants were identified in 61.1% (11 of 18) of positive cases, while Type 2 insertion variants accounted for 38.9% (7 of 18). Patients with Type 1 mutations exhibited significantly higher baseline platelet counts (mean 942.5 ± 124.0 × 10⁹/L) compared to Type 2 variants (mean 612.4 ± 84.0 × 10⁹/L, P < 0.05). However, Type 2 insertion variants correlated with a higher risk of transformation into secondary myelofibrosis over a 24-month observation window. Screening for these distinct calreticulin subclasses provides essential prognostic utility for guiding individualized maintenance therapies.
Keywords: Essential thrombocythemia, Calreticulin mutation, deletion variants, insertion variants, molecular genetics
Manuscript Timeline: Received: January 10, 2019; Revised: February 18, 2019; Accepted: March 12, 2019; Published: April 14, 2019