HOXB1 and microtia: Based on the etiological subtype, microtia can be classified into: 1) monogenic form, namely microtia attributed to mutations or alterations in a single gene (HOXA and HOXD gene clusters, TCOF1, POLR1C, POLR1D, and GLI3) [4], another study identified candidate genetic variants for microtia, such as the HOX (HOXA1/HOXB1/HOXA2), SIX, EYA, and TBX1 [5]; 2) chromosomal aberrations, when chromosomal abnormalities occur, such as deletions, duplications, or rearrangements.