PSEUDOHYPERTROPHIC TYPE

PSEUDOHYPERTROPHIC TYPE

(Duchenne type)

PSEUDOHYPERTROPHIC TYPE this occurs only in males. It is transmitted by a sex-linked recessive gene. Females carry the disease through gene but males are the victims of it. One-third of the cases, however, develops by spontaneous mutation. Recently a locus has been found in Xp 21 region of X chromosome. The disease may start in foetal life but in about 50% of cases it is manifested in second or third year of life, at times it may start later between 4-7 years. First of all, the pelvic girdle muscles are affected and ultimately there is involvement of shoulder girdle muscles. In a considerable number of cases to start with Pseudohypertrophy is seen. This is seen in glutei, calf muscles, quadriceps, deltoid and in infraspinati. These muscles look bulkier from outside but motor power and tone are less, jerks are dull. On voluntary contraction the affected muscles do not become hard and globular. The firm fleshy feel is lost. Concomitant to this pseudohypertrophy, some muscles also show atrophy. Pectoralis major is one such muscle which becomes so thin that it may be aptly compared to a parchment paper. In course of time all muscles showing pseudohypertrophy will have this fate and they all will be atrophic. Gradually contracture develops.

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As a result of weakness of the affected muscle groups, patient cannot walk in a normal manner. There is frequent falls during walk. Climbing up or rising up from the floor becomes difficult. Gait is peculiar. Patient stands on a broad base with a lordosis of the lumber spine, the whole chest is thrown in a forward plane and during stepping the patient swings this way and that, like that of a duck. This type of gait is called waddling or Duck gait. In the early stages instead of this gait patient may show just a limping gait and in the terminal stages when in an attempt to do so the patient crawls on the ground. This called Frog-like gait.

From lying down position when the patient tries to get up he rolls over his body to one side, then supports on the ground by his one or both hands, then on his feet, knees and waist and then stands up as if he is climbing up his own body. This is called Rising Test or Gower’s sign and is very characteristic (See Fig. 10.27).

Due to weakness of the shoulder girdle muscles hanging by the support of his axillae becomes difficult and the patient falls down. Death occurs usually in the second decade from inanition or respiratory infection. Heart is sometimes affected.

INVESTIGATIONS OF PSEUDOHYPERTROPHIC TYPE

(a) Muscle biopsy shows islands of necrosed myofibrils in a vast ocean of fibrofatty tissue.

(b) EMG shows a myopathic pattern.

(c) Enzyme study: Serum Aldolase is raised. CPK is elevated (100 to 200 times the normal level).

Carrier detection: In carrier females 70% will have raised CPK. The remaining 30% will have abnormality of EMG or muscle biopsy.

(d) Dystrophin level is very much reduced or absent in the muscles, By genetic studies the disease can be recognised in early pregnancy in about 95% of cases, and in late pregnancy by DNA probe from foetal tissue obtained by amniocentesis.