Total submissions: 1
Submitter | RCV | SCV | Clinical significance | Condition | Last evaluated | Review status | Method | Comment |
---|---|---|---|---|---|---|---|---|
Institute for Clinical Chemistry and Laboratory Medicine, |
RCV003325446 | SCV004031421 | pathogenic | Thrombocytopenia, X-linked, with or without dyserythropoietic anemia | 2023-09-04 | criteria provided, single submitter | clinical testing | We identified this variant in 3 individuals from one family (PMID: 36231035). The index patient is hemizygous for this variant, his daughter and mother heterozygous. The index patient and his daughter suffer from hematoma and frequent epistaxis (ISTH BAT score index = 9; Daughter = 5) and presented with macrothrombocytes. Additionally, the index had thrombocytopenia, however the daughter had no thrombocytopenia but mild spherocytosis and hemolysis. Flow cytometry and electron microscopy analysis supported a combined α-/δ (AN-subtype)-storage pool deficiency as cause for impaired agonist-induced platelet aggregation (light transmission aggregometry) and granule exocytosis (flow cytometry) in the index and affected daughter. In addition, both presented with mild dyserythropoiesis (Lu(a-b-); high HbF), which was altered in the daughter by the missense variant NM_000342.4(SLC4A1): c.2210C>T, resulting in a mild spherocytic phenotype. We were able to prove that the affected daughter had skewed X inactivation in favor of the affected allele (~86% activity). It was not possible to examine the variant-bearing but apparently healthy mother of the index case, but we suspect random X inactivation. The variant is highly conserved, rare as it is not known in dbSNP, and prediction tools (Mutation Taster, PolyPhen2, SIFT, PROVEAN) all predict pathogenicity. It is located between the C-terminal zinc finger and the nuclear localization sequence of GATA1. In this region (aa283–300), no common variants (MAF > 1%) and only two pathogenic variants also causing XLT with mild anemia have been reported (PMID: 27342114, 36291092, 35446378). Therfore, we classified this variant as pathogenic. |