Chromosomal Recessive transmission

Hunter s syndrome (type II) Initially, this disease was erroneously classified as type I-H. Its nosological independence and X-chromosomal recessive transmission were recognized in 1964 (A. Nja). The disease is based on a deficiency of L-iduron-sulphate sulphatase and sulphoiduronate sulphatase. The syndrome may appear in a moderate or severe form. 

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. 

Hepatic glycogenosis (type VI) (G.H. Hers, 1959) is due to hepatic phosphorylase deficiency. Subtype Via is caused by a lack of phos-phorylase-B kinase, and it is transmitted by the x-chromosomal recessive route. Subtype Vib shows a deficiency in glycogen phosphorylase, and its transmission is autosomal recessive. In the musculature, the analogous enzyme is, however, intact. Nevertheless, there is pronounced genetic and phenotypical heterogeneity. 

X-linked recessive disorders are also caused by mutations in genes on the X chromosome. Males are more frequently affected than females, and the chance of passing on the disorder differs between men and women. Families with an X-linked recessive disorder often have affected males, but rarely 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). 

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