CASE REPORT: A 3-month-old baby boy was presented with neonatal anaemia and mild hepatomegaly. Full blood count revealed severe hypochromic microcytic anaemia. There was an abundance of HbH inclusion bodies in his red blood cells. High-performance liquid chromatography showed a reduced HbA2 level with the presence of pre-run peak. Capillary electrophoresis showed the presence of HbH and Hb Barts. Molecular analysis found a common α0-thalassaemia (--SEA) in one allele and mutation in codon 125 in the other allele.
DISCUSSION: Non-deletional HbH disease due to a combination of deletional and non-deletional mutations may present with severe clinical manifestations than those with deletion mutations, which warrants accurate diagnosis using molecular techniques.
METHODS: For this cross-sectional study, patient blood samples that showed a positive peak in zone 2 of CE were selected. Hemoglobin and DNA of the samples were investigated to ascertain the presence and levels of non-deletional and deletional α thalassemia. The results were statistically analyzed.
RESULTS: Of the 137 samples investigated, 118 (86.1%) were positive for termination codon Hb CS mutation. Heterozygous Hb CS was found in 92 (67.2%), compound heterozygous Hb CS in 22 (16.1%), and homozygous Hb CS in four (2.9%) samples. The ranges of Hb CS level for heterozygous Hb CS, compound heterozygous Hb CS, and homozygous Hb CS were within 0.2-2.7%, 0.3-2.2%, and 4.5-5.5%, respectively. Significant hematological differences in the Hb level, mean cell volume, mean cell hemoglobin, red cell distribution width, red blood cell count, and Hb CS level were observed between heterozygous, homozygous, and compound heterozygous Hb CS.
CONCLUSIONS: In view of the overlapping prevalence range of Hb CS level for heterozygous and compound heterozygous Hb CS, only Hb CS level within the range 4.5-5.5% was helpful in the diagnosis of homozygous Hb CS.
METHODS: Forty BCR-ABL1-negative MPN patients' DNA: 19 polycythemia vera (PV), 7 essential thrombocytosis (ET) and 14 primary myelofibrosis (PMF), were screened for CALR mutations by CSGE. PCR primers were designed to amplify sequences spanning between exons 8 and 9 to target the mutation hotspots in CALR. Amplicons displaying abnormal CSGE profiles by electrophoresis were directly sequenced, and results were analysed by BioEdit Sequence Alignment Editor v7.2.6. CSGE results were compared with AS-PCR and confirmed by Sanger sequencing.
RESULTS: CSGE identified 4 types of mutations; 2 PMF patients with either CALR type 1 (c.1099_1150del52) or type 2 (c.1155_1156insTTGTC), 1 ET patient with nucleotide deletion (c.1121delA) and insertion (c.1190insA) and 1 PV patient with p.K368del (c.1102_1104delAAG) and insertion (c.1135insA) inframe mutations. Three patients have an altered KDEL motif at the C-terminal of CALR protein. In comparison, AS-PCR only able to detect two PMF patients with mutations, either type 1 and type 2.
CONCLUSION: CSGE is inexpensive, sensitive and reliable alternative method for the detection of CALR mutations in BCR-ABL1-negative MPN patients.