Hemiplegic migraine and MA/MO also occur as a comorbidity in proximal renal tubular acidosis (pRTA) patients carrying certain homozygous mutations in the SLC4A4 gene (encoding the Na+-HCO3− cotransporter NBCe1), in which mutations in the other known FHM-related genes were ruled out (Suzuki et al., 2010). Here, SLC4A4 is linked to proximal renal tubular acidosis.