| atypical achromatopsia | Incomplete achromatopsia with normal visual acuity and no nystagmus. Compare: dyschromatopsia. (05 Mar 2000) |
|---|---|
| atypical bacterial forms | Microorganisms that have undergone greater changes than normal in morphology, physiology, or cultural characteristics. (12 Dec 1998) |
| atypical cell | Not usual, abnormal. Cancer is the result of atypical cell division. (09 Oct 1997) |
| atypical facial neuralgia | Periodic pain in any region of the face, teeth, tongue, and occasionally in the occipital or shoulder area, which lasts several minutes to several days but has no trigger point and lacks the paroxysmal character of tic douloureux. Synonym: atypical facial neuralgia. (05 Mar 2000) |
| atypical fibroxanthoma | A solitary, often ulcerated, small cutaneous benign tumour composed of foamy histiocytes, spindle cells, and bizarre giant cells; usually found on the exposed skin of older people; microscopically, atypical fibroxanthoma closely resembles malignant fibrous histiocytoma, but originates in the dermis. (05 Mar 2000) |
| atypical gingivitis | Intense hyperaemic oedema and inflammation of the gingiva resulting from a hypersensitivity reaction. A dense plasma cell infiltrate is seen in the lamina propria. Synonym: atypical gingivitis. (05 Mar 2000) |
| atypical lipoma | <tumour> Lipoma, occurring primarily in older men on the posterior neck, shoulders, and back, which is benign but microscopically atypical, containing giant cells with multiple overlapping nuclei forming a circle. Synonym: pleomorphic lipoma. (05 Mar 2000) |
| atypical measles | Sometimes severe, unusual clinical manifestation of natural measles virus infection in persons with waning vaccination immunity, particularly in those who had received formaldehyde-inactivated vaccine; an accelerated allergic reaction apparently resulting from an anamnestic antibody response, characterised by high fever, absence of Koplik's spots, a shortened prodromal period, atypical rash, and pneumonia. (05 Mar 2000) |
| atypical melanocytic hyperplasia | Proliferation of melanocytes showing nuclear atypicality, especially as scattered single cells high in the epidermis; interpreted by some pathologists as malignant melanoma in situ. (05 Mar 2000) |
| atypical mycobacteria | Species of mycobacteria other than M. Tuberculosis or M. Bovis that can cause disease in immunocompromised humans. (05 Mar 2000) |
| atypical mycobacterial infection | <microbiology> Infection with organisms from the Mycobacterium genus other than tuberculosis. Risk factors include immunocompromised patients and those with AIDS. Mycobacterium avium intracellulare is an example which frequently infects AIDS patients. Atypical mycobacterial infections can cause abscesses, septic arthritis and osteomyelitis. Treatment can be difficult due to the emergence of resistance to standard antitubercular antibiotics. (27 Sep 1997) |
| atypical nevi | <dermatology> Moles whose appearance is different than normal moles. They may be larger and have irregular borders. Their colour may not be uniform and they may be flat or raised above the skin surface. Any mole that appears irregular may be suspect for skin cancer. (16 Dec 1997) |
| atypical pneumonia | <chest medicine> This refers to a type of pneumonia that does not follow the typical signs and symptoms of pneumonia. A number of different viral and bacterial agents have been identified which can cause this form of respiratory infection. Examples include Chlamydia pneumonia, psittacosis, Mycoplasma, influenza A or B, adenovirus and Legionella. Antibiotics will be necessary in all but the mildest cases. Symptoms generally improve in less than 2 weeks. (27 Sep 1997) |
| atypical pseudocholinesterase | A genetic variant of cholinesterase that fails to catalyze the hydrolysis of succinylcholine. See: dibucaine number, fluoride number. (05 Mar 2000) |
| atypical trigeminal neuralgia | Periodic pain in any region of the face, teeth, tongue, and occasionally in the occipital or shoulder area, which lasts several minutes to several days but has no trigger point and lacks the paroxysmal character of tic douloureux. Synonym: atypical facial neuralgia. (05 Mar 2000) |