| D81 | Combined immunodeficiencies | NON-BILLABLE CODE |
| D81.0 | Severe combined immunodeficiency [SCID] with reticular dysgenesis | BILLABLE CODE |
| D81.1 | Severe combined immunodeficiency [SCID] with low T- and B-cell numbers | BILLABLE CODE |
| D81.2 | Severe combined immunodeficiency [SCID] with low or normal B-cell numbers | BILLABLE CODE |
| D81.3 | Adenosine deaminase [ADA] deficiency | NON-BILLABLE CODE |
| D81.30 | Adenosine deaminase deficiency, unspecified | BILLABLE CODE |
| D81.31 | Severe combined immunodeficiency due to adenosine deaminase deficiency | BILLABLE CODE |
| D81.32 | Adenosine deaminase 2 deficiency | BILLABLE CODE |
| D81.39 | Other adenosine deaminase deficiency | BILLABLE CODE |
| D81.4 | Nezelof's syndrome | BILLABLE CODE |
| D81.5 | Purine nucleoside phosphorylase [PNP] deficiency | BILLABLE CODE |
| D81.6 | Major histocompatibility complex class I deficiency | BILLABLE CODE |
| D81.7 | Major histocompatibility complex class II deficiency | BILLABLE CODE |
| D81.8 | Other combined immunodeficiencies | NON-BILLABLE CODE |
| D81.81 | Biotin-dependent carboxylase deficiency | NON-BILLABLE CODE |
| D81.810 | Biotinidase deficiency | BILLABLE CODE |
| D81.818 | Other biotin-dependent carboxylase deficiency | BILLABLE CODE |
| D81.819 | Biotin-dependent carboxylase deficiency, unspecified | BILLABLE CODE |
| D81.82 | Activated Phosphoinositide 3-kinase Delta Syndrome [APDS] | BILLABLE CODE |
| D81.9 | Combined immunodeficiency, unspecified | BILLABLE CODE |
