| MED subtype / label | Gene | Inheritance | Key notes / phenotype pointers | Citations |
|---|---|---|---|---|
| MED type 1 (OMIM 132400); COMP-MED / EDM1 | **COMP** | AD | Most common MED subtype; reported as up to half of MED cases. In the 2025 cohort, **13/25 patients (52%)** and **7/12 families (58.3%)** had COMP variants. COMP-associated disease tended to be more severe and accounted for most orthopedic surgeries; radiographically often shows **small round epiphyses** and **dysplastic acetabula**. Dikova 2024 also states **pathogenic COMP variants account for ~50% of AD MED**; de novo COMP variants occur. | (pqac-00000019, pqac-00000020, pqac-00000018) |
| MED type 5 (OMIM 607078) | **MATN3** | AD | Established dominant MED gene. In the 2025 cohort, **5/25 patients (20%)** and **2/12 families (16.6%)** had MATN3 variants. Radiographically associated with **flattened epiphyses** in the cohort discussion. | (pqac-00000019, pqac-00000020) |
| MED type 6 (OMIM 614135) | **COL9A1** | AD | Listed among dominant MED genes in recent cohort/mechanistic summaries; part of collagen IX–related MED spectrum. Specific cohort frequency not reported in the retrieved evidence. | (pqac-00000019, pqac-00000021) |
| MED type 2 (OMIM 600204) | **COL9A2** | AD | Listed among dominant MED genes. In the 2025 cohort, **2/25 patients (8%)** and **1/12 families (8.3%)** had COL9A2 variants. One inherited intronic splice-region variant was noted; COL9A2-related disease may show relatively prominent knee involvement in prior literature. | (pqac-00000019, pqac-00000020) |
| MED type 3 (OMIM 600969) | **COL9A3** | AD | Listed among dominant MED genes in recent sources; no cohort frequency provided in the retrieved evidence. | (pqac-00000019, pqac-00000021) |
| MED type 4 / MED-4 (MIM 226900); recessive MED; **DTDST-related** | **SLC26A2** (*alias* **DTDST**) | AR | Recessive MED caused by **biallelic** SLC26A2 variants. In the 2025 cohort, **5/25 patients (20%)** and **2/12 families (16.6%)** had SLC26A2 variants. Phenotype pointers include **double-layered/bipartite patella** (reported as relatively specific; ~60% in one source) and **glacier sign**. Severity across the SLC26A2 spectrum relates partly to residual sulfate-transporter activity, though correlation is not absolute. | (pqac-00000019, pqac-00000020, pqac-00000021, pqac-00000022) |
| MED type 7 (OMIM 617719) | **CANT1** | AR | Recently described recessive MED subtype due to **biallelic CANT1** variants. Cohort source notes MED type 7 may occur **without classic Desbuquois features**. Frequency not reported in the retrieved MED cohort because no CANT1-positive family was identified there. | (pqac-00000019, pqac-00000032) |
| Historical gene list in older reviews/case reports | **DTDST** | AR | **DTDST is an older alias for SLC26A2**, not a separate gene. Older MED literature/case reports may list causal genes as COMP, DTDST, MATN3, COL9A1, COL9A2, and COL9A3. | (pqac-00000018, pqac-00000023) |


*Table: This table summarizes the main genes currently implicated in multiple epiphyseal dysplasia, their inheritance patterns, and distinguishing phenotype clues. It also highlights cohort frequencies from Daşar 2025 and the reported ~50% contribution of COMP variants to autosomal dominant MED from Dikova 2024.*