The role of genetic testing in accurate diagnosis of X-linked sideroblastic anemia: novel ALAS2 mutations and the impact of X-chromosome inactivation
Bibliographic record
Abstract
X-linked sideroblastic anemia (XLSA) is a hereditary disorder affecting heme biosynthesis, caused by mutations in the ALAS2 gene, which encodes the erythroid-specific enzyme 5-aminolevulinate synthase. This enzyme, which requires pyridoxal 5'-phosphate (PLP) as a cofactor, catalyzes the first and rate-limiting step of heme synthesis in erythroid cells. XLSA is characterized by hypochromic microcytic anemia and ring sideroblasts in bone marrow, with most patients showing variable degrees of response to pyridoxine supplementation; however, female carriers of ALAS2 mutations often present a distinct clinical phenotype. A comprehensive review of the literature reveals over 100 distinct ALAS2 mutations linked to XLSA in more than 240 families. Here, we report seven new patients (four female cases) initially diagnosed with various conditions, later confirmed to have X-linked Sideroblastic Anemia due to ALAS2 mutations through genetic analysis. Among these, five represent novel ALAS2 mutations, including the first ever reported stop-loss mutation in ALAS2 associated with XLSA rather than X-linked dominant protoporphyria (XLDPP). Computational modelling of six reported cases revealed that four mutations significantly impact protein structure, conformation and cofactor interaction, consistent with our enzymatic assays demonstrating reduced ALAS2 activity. Furthermore, X-chromosome studies in female probands revealed a pronounced skewing of X-chromosome, which may provide an explanation for their distinct clinical manifestations in females.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".