This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 136 of the KCNJ11 protein (p.Arg136Cys). This variant is present in population databases (rs766891274, gnomAD 0.004%). This missense change has been observed in individual(s) with autosomal recessive congenital hyperinsulinism (PMID: 21422196). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 435558). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt KCNJ11 protein function with a positive predictive value of 95%. This variant disrupts the p.Arg136 amino acid residue in KCNJ11. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 20686794, 28442472). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic.

The c.406C>T variant in KCNJ11 is a missense variant predicted to cause substitution of arginine to cysteine at amino acid 136. This variant is rare in the general population with a frequency below the threshold expected for the associated phenotype(s). This variant has been observed in affected individual(s) with monoallelic occurrence (heterozygous/hemizygous) (PMID: 20685672, 34465386). A different variant at the same position has been determined to be Pathogenic or Likely Pathogenic. Computational prediction algorithms indicate this variant is likely to affect gene or protein function. Given the available evidence, this variant is classified as Likely Pathogenic.