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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    MUSCULAR DISORDERS one of the parents. If an individual does not develop the trait himself, it never occurs in any of his descendants. While there is a wide variability in expressivity, the penetrance is complete. There is no significant difference in the frequency of expression in males and females. Inasmuch as there is no record of two affected individuals marrying, no opportunity for observing the expression of the trait in the homozygous condition has been made possible and it is not known, there¬ fore, whether or not dominance is complete. Since all matings involving the trait are between an affected and a normal individual, a 1 : 1 ratio is expected. Table IT shows a comparison of observed and expected ratios TABLE I Pattern of Muscular Involvement in Facio-scapulo-humeral Dystrophy in 58 Patients (Tyler and Stephens, 1950) Degree of involvement of certain muscles in typical cases at different stages Minimal i Slight j Moderate Severe Facial except orbicularis oris and zygomaticus Orbicularis oris ------ Zygomaticus ------- Sternomastoid, sternal head - - - - Pectoralis major, sternal head - - Pectoralis major, clavicular head - - - Deltoid ------- Triceps and biceps - - - _ _ Brachioradialis ------ Trapezius, upper fibres - - - _ Trapezius, middle and lower fibres Rhomboids - - - - - - Latissimi ------- Abdominals and recti abdominus - - Glutei ------- Thigh groups - - - - - Tibials - - Peroneals - - - - - Calf group ------- Hands, fore-arms, feet- - - _ _ 0 = No change. 1 = Atrophy with significant weakness. 2 = Moderate atrophy and weakness. 3 =- Severe disability. 4 = No muscle detectable. TABLE II A Comparison of the Number of Dystrophic with the Number of Normal Offspring in Families where one Parent is Dystrophic (Tyler and Stephens, 1950) 290