Clinical genetics / edited by Arnold Sorsby.

Date:
1953
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Clinical genetics / edited by Arnold Sorsby. Source: Wellcome Collection.

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    CLINICAL VARIETIES OF GENETIC DISEASE constitution of the patient. A blow which would give little pathological disturb¬ ance in one individual may lead to fracture of the femur in a patient with fragilitas ossium of genetic origin. Exposure to tuberculous infection will precipitate clinical tuberculosis in members of some families as readily as it does in strains of rabbits bred for special susceptibility to tuberculosis, whilst similar exposure will not harm other individuals, or animals from strains bred for special insusceptibility to tuberculosis. Doubtful specificity of clinical appearances Furthermore, the appearances of an affection definitely of genetic or definitely of environmental origin may be clinically indistinguishable. Optic atrophy, whether derived genetically or caused by injury to the optic nerve, will look very much alike and will give the same blindness. Mental deficiency may be genetic in origin or caused by many different environmental factors ; disseminated sclerosis cannot always be readily distinguished as of genetic or of environmental origin. Pedigrees such as shown in Fig. 1, which depicts all the three members of a sibship О ^ ^ <> imi 0 Q Э 4 ED Cerebral syphilis Paralysis: aortitis Tabes Juvenile tabes Died, aged 57 years, from a stroke Fig. 1.—Occurrence of syphilis of central nervous system in a family. Pedigree. (After F. Curtius and H. Schlatter (1934). Dtsch. Z. Nervenheilk., 134, 44.) This pedigree illustrates the difficulty in incriminating an environmental or a genetic factor in a particular situation. as suffering from juvenile tabes, and both their parents also affected with syphilis of the central nervous system, suggest a genetically determined susceptibility of the central nervous system to the pathogen of syphilis, or alternatively that these individuals harboured a spirochaete with a special affinity for the central nervous system. Both suppositions are speculative, but they emphasize the difficulty in ascribing a fully developed clinical condition to a definitely environmental or definitely genetic origin. The same difficulty may be met in the course of an affection that has not yet run to its end stage. Plate I shows successive stages of a generalized fundus dystrophy that is dominant in character and sets in at about the age of 40 years. The earliest stage is indistinguishable from the fundus reactions seen in vascular or metabolic disturbances; it could be taken for an illustration of neuro- retinitis . At later stages appearances generally interpreted as the result of 2
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