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Gardos channelopathies: novel insights into KCNN4 mutations and their clinical impact

Journal of Human Genetics volume 71, pages 169–176 (2026) Cite this article

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Abstract

Gardos channelopathies are rare hereditary hemolytic anaemias caused by mutations in the KCNN4 gene, which encodes the calcium-activated potassium channel (KCa3.1) in red blood cells. In this study, we report three unrelated Indian patients with unexplained chronic hemolytic anaemia. Whole exome sequencing revealed distinct KCNN4 mutations: a homozygous c.5G > A mutation (p.Gly2Asp) in Case I, a compound heterozygous condition with the Hb Nottingham mutation (HBB: c.296T > G) and a splice-site mutation in KCNN4 (c.931-1G > C) in Case II, and homozygous c.541A > T mutation (p.Ser181Cys) in Case III. All three patients presented with chronic anaemia, indirect hyperbilirubinemia, reticulocytosis, and recurrent blood transfusions. Red cell enzyme studies (G6PD, PK, GPI) showed normal activities, and flow cytometry-based EMA binding was normal. Haemoglobin electrophoresis by HPLC was normal, except in Case II, and tested positive for unstable haemoglobin using a heat instability test. Flow cytometry revealed significantly elevated intracellular calcium levels and reactive oxygen species (ROS) in all cases, indicating oxidative stress under osmotic stress. In Case III, a Percoll density gradient assay demonstrated dehydrated erythrocytes, supporting the diagnosis. This study expands the mutation spectrum of Genetic diagnosis using NGS, which is essential for appropriate clinical management and genetic counselling in unexplained cases of hemolytic anaemia. Elevated intracellular calcium levels play a key role in hemolysis, suggesting that calcium-modulating therapies could aldehyleviate symptoms.

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Fig. 1: Morphological and Molecular Characterization of Hb Nottingham Variant in Case 2.
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Fig. 2: Flow cytometric analysis comparing patients and healthy controls.
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Fig. 3: Percoll density gradient centrifugation of whole blood samples from healthy control and case III.
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Fig. 4
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Acknowledgements

We sincerely appreciate the cooperation and participation of the patients and their families in this study, which was conducted with the support of the Indian Council of Medical Research, New Delhi. Additionally, we extend our gratitude to the Department of Health Research (DHR), Ministry of Health and Family Welfare, Government of India. The reference number for this funding is File No. R.12020/08/2024-HR/E-Office: 8292872.

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Authors and Affiliations

  1. Department of Haematogenetics, ICMR-National Institute of Immunohematology, 13th Floor, NMS Building, King Edward Memorial (KEM) Hospital Campus, Parel, Mumbai, India

    Prashant Warang, Pradnya Dehadrai, Neha Samanpalliwar, Rashmi Dongerdiye, Tejashree Anil More, Ashish Chiddarwar, Pallavi Thaker, Prachi Kamble, Arati Saptarshi, Manisha Madkaikar & Prabhakar S. Kedar

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  1. Prashant Warang
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  2. Pradnya Dehadrai
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  11. Prabhakar S. Kedar
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Contributions

PW, PSK and MM: conceptualisation, data curation, funding acquisition, investigation, project administration, writing-review and editing. PW and PSK: original draft. AS, TAM, PK, AC, PM, PD and RD: laboratory data analysis, molecular experimental work, sequencing experiments and variant validation. All authors participated in the data discussion and read and approved the manuscript. All authors have read and agreed to the published version of the manuscript.

Corresponding author

Correspondence to Prabhakar S. Kedar.

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The authors declare no competing interests.

Consent to participate

Written informed consent was obtained from all patients before blood collection. Written informed consent was obtained for all participants in this study.

Ethical Statement

This study has been approved by the Institutional Ethics Committee for Research on Human Subjects, ICMR-National Institute of Immunohaematology, 13th Floor, New M.S. Building, KEM Hospital Campus, Parel, Mumbai-400012. The project reference number is ICMR/NIIH/IEC/09/2024. This study was conducted in accordance with the 1964 Declaration of Helsinki.

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Warang, P., Dehadrai, P., Samanpalliwar, N. et al. Gardos channelopathies: novel insights into KCNN4 mutations and their clinical impact. J Hum Genet 71, 169–176 (2026). https://doi.org/10.1038/s10038-025-01414-1

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