Hb Jambol: a new hyperunstable hemoglobin causing severe hemolytic anemia.

Area of Science:

• Genetics
• Molecular Biology
• Hematology

Background:

• Hemoglobinopathies are a group of inherited blood disorders affecting hemoglobin synthesis.
• Beta-thalassemia and related disorders are often caused by mutations in the beta-globin gene.
• Accurate molecular diagnosis is crucial for understanding disease mechanisms and patient management.

Observation:

• A de novo mutation causing a hyperunstable beta-chain variant (Hb Jambol) was identified in a 2-year-old Bulgarian girl.
• The patient presented with severe hemolytic anemia, indicating significant disruption of red blood cell function.
• RNA/DNA analysis revealed a complex genomic rearrangement involving insertions and deletions within the beta-globin gene locus.

Findings:

• The genomic rearrangement resulted in a deletion of 4 amino acids and an insertion of 9 amino acids at positions 105-108 of the beta-chain.
• This alteration created an elongated beta-chain of 151 amino acids, leading to extreme instability.
• The specific rearrangement involved a 23-nucleotide insertion, a 310-nucleotide deletion, and a 28-nucleotide insertion derived from an inverted sequence.

Implications:

• This case highlights the diverse and complex mechanisms underlying hemoglobinopathies.
• The identification of Hb Jambol expands the spectrum of known beta-globin gene mutations.
• Understanding such complex rearrangements is vital for genetic counseling and potential therapeutic strategies.