In line with this, for MCD patients with TUBG1 mutations, for whom HC size at birth was available, values appeared within the normal range (p.L387P, HC = 31 cm; p.Y92C, HC = 33 cm), but then progressed to severe reduction (p.L387P, HC = −5,5 SD; p.Y92C, HC = −4SD), suggesting a secondary microcephaly that mainly develops after birth. The gene discussed is TUBG1; the disease is microcephaly.