Page 284 - Haematologica Vol. 107 - September 2022

CASE REPORT
tient’s erythrocyte membrane proteins to assess if the novel identified variant might cause FP (GoF variants as- sociated with no impairment of the protein expression) or Lan- blood group (loss-of-function variants associated with downregulation or absence of the protein ex- pression).5 We demonstrated no alterations of protein ex- pression in the patient compared to healthy controls (Figure 1D and E). Thus, the occurrence of this ABCB6 pa- thogenic variant suggested an explanation for the pa- tient's increased serum K values, and functional studies of temperature dependence confirmed the diagnosis of FP.
The presence of the PIEZO1 variant suggested the diagno- sis of DHS.14 This finding further explained the altered per- meability of the RBC, the hepatosiderosis, and the post-splenectomy exacerbation of phenotype. The diag- nosis of DHS was further confirmed through ektacyto- metry analysis. Deformability of RBC of the patient and of control subjects was evaluated by osmotic gradient ekta- cytometry using the laser-assisted optical rotational cell analyzer (LORCA), as previously described.15 Ektacytometry revealed a left shift of the osmotic curve and a slightly decreased DiMax in the proband compared to healthy controls (Figure 1F). This peculiar curve is typical of multi- locus inheritance caused by the combined presence of HS and DHS, as recently demonstrated.15
The proband was thus diagnosed, at 54 years of age, with anemia caused by multilocus inheritance (HS, DHS, FP) of mutations in the SLC4A1, PIEZO1, and ABCB6 genes. This paradigmatic clinical case underlines the dual importance of correct clinical assessment and genetic diagnosis to guide personalized clinical management of the patient. Earlier diagnosis of DHS would certainly have prevented the splenectomy and ensuing thrombotic complications. This case confirms the importance of NGS-based testing in the diagnostic workflow of hereditary anemias for com- plete differential diagnosis in both research and clinical settings.
Authors
Barbara Eleni Rosato,1,2 Seth L. Alper,3 Giovanna Tomaiuolo,2,4 Roberta Russo,1,2 Achille Iolascon1,2# and Immacolata Andolfo1,2#
1Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli ‘Federico II’, Napoli, Italy; 2CEINGE
References
1. Iolascon A, Andolfo I, Russo R. Advances in understanding the pathogenesis of red cell membrane disorders. Br J Haematol.
Biotecnologie Avanzate, Napoli, Italy; 3Renal Division and Vascular Biology Research Center, Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical School, Boston, MA, USA and 4Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, University of Naples Federico, Naples, Italy.
#AI and IA contributed equally as co-senior authors.
Correspondence:
I. ANDOLFO - immacolata.andolfo@unina.it R. RUSSO - roberta.russo@unina.it
https://doi.org/10.3324/haematol.2022.280799
Received: February 7, 2022. Accepted: April 8, 2022. Prepublished: April 21, 2022.
©2022 Ferrata Storti Foundation Published under a CC BY-NC license
Disclosures
SLA has received research funding from and consults for to Quest Diagnostics, Inc.
Contributions
IA, AI, and RR designed and conducted the study and prepared the manuscript; RR and IA performed in silico design of the NGS panels and interpretation of the genetic variants; BER prepared the initial draft of the manuscript; BER prepared the library enrichment, performed the Sanger sequencing analysis and western blotting analysis; AI cared for the patient; GT performed the ektacytometry analysis; SLA carried out a critical revision of the manuscript.
Acknowledgments
The authors kindly thank Prof. Carlo Brugnara for the critical revision of the manuscript and Prof. G. Stewart for the ion flux measurement.
Funding
This research was funded by an EHA Junior Research Grant to IA (grant number: 3978026), and by Bando Star Linea 1 - Junior Principal Investigator Grants - COINOR, Università degli Studi di Napoli ‘Federico II’ to RR.
Data-sharing statement
The original data and protocols are available to other investigators upon request.
2019;187(1):13-24.
2. Andolfo I, Russo R, Gambale A, Iolascon A. New insights on
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