Panel A: A three-generation family pedigree chart shows the affected individuals with solid black squares, unaffected individuals with white shapes, and individuals not genotyped with grey shapes. The proband (3.d) and affected sibling (3.e) are indicated. Panel B: Two line graphs display the absolute neutrophil count (ANC) and absolute lymphocyte count (ALC) over time for individuals 3.d and 3.e. The ANC graph shows fluctuations in neutrophil counts, while the ALC graph shows changes in lymphocyte counts. The period of G-CSF treatment for 3.d is marked by vertical dotted lines. Panel C: Three line graphs depict the counts of CD3 positive T cells, CD19 positive B cells, and CD3 negative NK cells over the clinical course for 3.d and 3.e. The CD3 positive T cells graph shows an increase in T cell counts, the CD19 positive B cells graph shows a consistent absence of B cells, and the CD3 negative NK cells graph shows a decline in NK cell counts. Panel D: Two timeline charts illustrate the clinical course pre-transplant for 3.d and 3.e, including the initiation of various treatments and procedures. Panel E: Two chromatograms show Sanger sequencing results of genomic DNA from the mother (2.b), proband (3.d), and affected sibling (3.e), identifying a variant within SEPTIN6 exon 10. Panel F: A chromatogram displays Sanger sequencing of complementary DNA (cDNA) from the mother (2.b), showing only the wildtype allele. Panel G: A diagram of the SEPTIN6 genetic locus highlights the identified mutation compared to a previously known mutation.
Clinical course of two affected siblings with X-linked SEPTIN6 stop-loss variants. (A) Three-generation family pedigree demonstrates proband (III.d; arrow) and affected sibling (III.e) with congenital neutropenia, dysmyelopoiesis with tetraploidy and aneuploidy, B cell aplasia, and variable T cell lymphopenia. Solid black squares are affected males. Unaffected individuals are either SEPTIN6 WT (white shapes) or not genotyped (gray). The sibling’s mother was an asymptomatic carrier. (B) ANC and ALC were enumerated for III.d and III.e. The period of G-CSF treatment for III.d is indicated via vertical dotted lines. (C) Serial lymphocyte subsets enumerated CD3+ T cells (top), CD19+ B cells (middle), and CD3−CD16+ and/or CD56+ NK cells (bottom) over the clinical course for III.d and III.e, respectively. (D) Clinical course pretransplant for the proband (III.d) and affected sibling (III.e) following the initial positive SCID NBS including initiation of weekly SCIG (green), SMX-TMP (blue) and voriconazole (purple) prophylaxis, vitamin B12 (orange), and G-CSF (red; 5 μg/kg/dose is 1 bar; max 20 μg/kg/dose). BMA/BM biopsies (asterisk) were collected as indicated. (E and F) Sanger sequencing of genomic DNA isolated from PBMCs from mother (II.b), proband (III.d), and affected sibling (III.e) identifies the variant (GRCh38 ChrX:119625378A>T) within SEPTIN6 exon 10 (NM_145799.4). (F) Sanger sequencing of complementary DNA (cDNA) converted from bulk PBMC mRNA from the mother (II.b) demonstrated only the WT allele was present. (G) Diagram of SEPTIN6 genetic locus highlighting the current identified mutation compared with the previously known mutation (5). The same neopeptide (LCCLLHAA*) extension is predicted to occur in both stop-loss variants. SCIG, subcutaneous immunoglobulin; SMX-TMP, sulfamethoxazole/trimethoprim; BMA, bone marrow aspirates.