| Abdominal wall defect | HP:0010866 | | |
| Abdominal wall muscle weakness | HP:0009023 | | |
| Abducens palsy | HP:0011349 | | |
| Abducted thumb | HP:0001234 | | |
| Aberrant melanosome maturation | HP:0007384 | | |
| Aberrant thyroid | HP:0100028 | | |
| Abetalipoproteinemia | HP:0008181 | | |
| Ablepharon | HP:0011224 | | |
| Ablepharon of eyelid | HP:0011224 | | |
| Abnormal acetylcarnitine profile | HP:0012071 | | |
| Abnormal activity of mitochondrial respiratory chain | HP:0011922 | | |
| Abnormal adiponectin level | HP:0030684 | | |
| Abnormal aggressive, impulsive or violent behavior | HP:0006919 | | |
| Abnormal albumin level | HP:0012116 | | |
| Abnormal aldolase level | HP:0012400 | | |
| Abnormal alpha-beta T cell morphology | HP:0030333 | | |
| Abnormal alpha granule content | HP:0012527 | | |
| Abnormal alpha granule distribution | HP:0012525 | | |
| Abnormal alpha granules | HP:0012483 | | |
| abnormal amniotic fluid | HP:0001560 | | |
| Abnormal amplitude of dark-adapted bright flash electroretinogram | HP:0030478 | | |
| Abnormal amplitude of dark-adapted dim flash electroretinogram | HP:0030476 | | |
| Abnormal amplitude of flash visual evoked potentials | HP:0030462 | | |
| Abnormal amplitude of light-adapted flicker electroretinogram | HP:0030479 | | |
| Abnormal amplitude of light-adapted single flash electroretinogram | HP:0030481 | | |
| Abnormal amplitude of pattern electroretinogram | HP:0030485 | | |
| Abnormal amplitude of pattern onset/offset VEP | HP:0030457 | | |
| Abnormal amplitude of pattern onset/offset visual evoked potentials | HP:0030457 | | |
| Abnormal amplitude of pattern reversal visual evoked potentials | HP:0000650 | | |
| Abnormal Amsler grid test | HP:0030590 | | |