Chromosomal Dominant transmission

Transmission is autosomal dominant, and the relevant gene has been mapped to the same locus on chromosome 19q as that associated with susceptibility to malignant hyperthermia (pages 318-319). It is not established that the conditions are allelic. Almost all patients with CCD whose muscle has been tested in vitro for... 

Genetic transmission in nemaline myopathy is the subject of some uncertainty. A Japanese study of 50 pedigrees came to the conclusion that autosomal dominant with reduced penetrance was the most probable mode. However a Finnish study presented evidence for autosomal recessive transmission. There is no evidence that severe and mild forms are genetically distinct and several pedigrees contain members showing widely differing clinical severity. A candidate gene for autosomal dominant nemaline myopathy has been localized to chromosome Iq 21—23. 

X-linked dominant disorders are caused by mutations in genes on the X chromosome. Females are more frequently affected than males, and the chance of passing on an X-linked dominant disorder differs between men and women. Families with an X-linked dominant disorder often have both affected males and affected females in each generation. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons (no male-to-male transmission). 

The frequency of this harmless disorder in the metabolism of bilirubin is quite high it affects 5-12% of the population. The syndrome is 4 times more common in men than in women. Frequency in the affected families lies between 5% and 55%. Genetic transmission occurs in a dominant autosomal way with differing degrees of penetrance, which accounts for the heterogeneous clinical picture. Sporadic occurrences of this syndrome have also been observed. The gene is located on chromosome 2. 

Porphyria variegata is caused by protoporphyrinogen oxidase deficiency. Transmission is autosomal dominant (chromosome 1 q 23). The frequency is 1 100,000. The clinical picture is characterized by skin changes similar to PCT (men > women), abdominal pain... 

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