Similar patterns of immunolocalization for SRY-box transcription factor 9 (SOX9) and the 2 major components of cartilage matrix, collagen type II α1 chain (COL2A1) and aggrecan (ACAN), were observed in the MPS IH and HD groups (Figure 1C and Supplemental Figure 1B). Here, SOX9 is linked to isolated hemihyperplasia.