Analogously to Kir4.1 defects, which predispose to autism-epilepsy comorbidity by altering the astrocytic-dependent potassium buffering [36], a defective ion trafficking due to GlialCAM mutations might cause osmotic imbalance and fluid accumulation [30,37,38] leading to the aforementioned macrocephalic-related spectrum of diseases. The gene discussed is HEPACAM; the disease is epilepsy.