Genetic defects presenting in the first year of life were more likely to lead to both a generalized HMD pattern and also developmental delay, as observed in patients with neurotransmitter defects (with the exception of dominant GCH1‐related disease) and those with ATP1A3, FOXG1, GNAO1, SLC2A1, and PDE10A variants.10, 11, 13, 14, 15. Here, SLC2A1 is linked to hereditary mucoepithelial dysplasia.