On the other hand, MMR deficiency and MSI may offer further treatment options with Programmed cell death protein (PD‐1)/ Pro PD‐1/programmed death‐ligand 1 (PD‐L1) inhibitors because such tumours may have an increased mutational burden and excess production of tumour neoantigens.24 The gene discussed is MRC1; the disease is hyperinsulinemic hypoglycemia, familial, 4.