| Congenital |
| Nonsyndromic |
| X-linked (XLSA) |
| Mitochondrial transporter SLC25A38 defects |
| Mitochondrial heat shock protein 70 (HSPA9) defects |
| Mitochondrial heat shock cognate protein 20 (HSCB) defects |
| Glutaredoxin 5 deficiency |
| Erythropoietic protoporphyria |
| Syndromic |
| X-linked with ataxia (XLSA/A) |
| Sideroblastic anemia, B cell immunodeficiency, periodic fevers, and developmental delay (SIFD) |
| Myopathy, lactic acidosis, and sideroblastic anemia (MLASA), and variants |
| Pearson marrow-pancreas syndrome |
| Thiamine responsive megaloblastic anemia (TRMA) |
| Syndromic or nonsyndromic |
| Autosomal of unknown cause |
| Sporadic congenital of unknown cause |
| Acquired |
| Clonal/neoplastic |
| MDS with ring sideroblasts and single lineage dysplasia (MDS-RS-SLD) |
| MDS with ring sideroblasts and multilineage dysplasia (MDS-RS-MLD) |
| Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) |
| Metabolic/reversible |
| Copper deficiency (zinc toxicity) |
| Drugs (eg, isoniazid, chloramphenicol, linezolid) |
| Excess alcohol use |
| Hypothermia |
