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Congenital Muscular Dystrophy
Neonates with congenital muscular dystrophy are hypotonic, weak, and may have distal arthrogryposis. Serum concentration of creatine kinase may be normal or elevated. Electromyographic findings are consistent with a myopathic process (brief, small, and abundant motor unit potentials).
Muscle biopsy shows variation in fiber size, a central nucleus, and replacement of muscle tissue by fibrosis and proliferation of adipose tissue. Merosin deficiency is present in some cases. Every patient with congenital muscular dystrophy should undergo MRI of the brain. The MRI of the brain of patients with Fukuyama type congenital muscular dystrophy shows migrational errors (polymicrogyria, lissencephaly, and heterotopia) and hypomyelination of the centrum semiovale.More about... 144

Myotubular Myopathy
Neonates with myotubular myopathy present with facial weakness, ptosis, ophthalmoplegia, generalized weakness and hypotonia, and, at times, with arthrogryposis. The severe form of myotubular myopathy courses with severe respiratory compromise which may lead to asphyxia. This malignant form occurs in males (X-linked inheritance). Myotubular myopathy is diagnosed based on muscle biopsy. Muscle biopsy with ATP-ase stain shows muscle fibers with one or more central nucleus, surrounded by a clear halo (area devoid of myofibrils). Prenatal diagnosis of the X-linked recessive form is accomplished by chorionic villus biopsy and DNA marker studies of the Xq28 region.More about... 146

Craniocarpotarsal Dysplasia
Craniocarpotarsal dysplasia, Freeman-Sheldon syndrome, and whistling face syndrome are synonyms. Craniocarpotarsal dysplasia is characterized by very peculiar facial features: a flat face with a crying-like expression, long philtrum, and a puckered mouth (as if ready to whistle). They have an H- or V-shaped groove on the chin (Figure 166.1 [A] [B]). Arthrogryposis is more marked in the upper extremities than in the lower extremities. Feeding problems are frequent. Patients with craniocarpotarsal dysplasia usually have normal intelligence. Craniocarpotarsal dysplasia is usually transmitted as an autosomal dominant disorder but autosomal recessive inheritance occurs in some families. The nature of this disease is not known. Muscle biopsy of the buccinator muscle reveals fibrous connective tissue replacing the muscle bundles.

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Figure 166.1. Freeman-Sheldon syndrome. [A] Typical facial characteristics; [B] distal arthrogryposis.

Schwartz-Jampel syndrome type 1 b
Schwartz-Jampel syndrome type 1 b is a recessively inherited condition condition linked to 1p34-p36. There is no genetic test to diagnose Schwartz-Jampel syndrome. Neonates with Schwartz-Jampel syndrome often have arthrogryposis. The diagnosis of Schwartz-Jampel syndrome in the neontal period requires the presence of myotonic discharges and bent-bone dysplasia. Bent-bone abnormality in neonates with Schwartz-Jampel syndrome probably result from bone remodeling because of abnormal muscle traction. The changes due to bone remodeling, as a result continuous muscle contraction are: flat face; hypognathium; pectus excavatum; pectus carinatum; bowing or external rotation of the femora, coxa vara, or valga; dysplasia or subluxation of the hips; retrocurvation of the knees; talipes valgus or planus; arthrogryposis; and osteoporosis. The differential diagnosis of Schwartz-Jampel syndrome includes other conditions that present with neonatal myotonia or bent-bone dysplasia or both, and arthrogryposis. These conditions are: (1) sodium-channel myotonia, which is a dominantly inherited condition and is not associated with bone dysplasia, (2) myotonic dystrophy, and (3) Stuve-Wiedmann syndrome.

Stuve-Wiedemann syndrome
Stuve-Widerman syndrome previously called Schwartz-Jampel syndrome type 2 is characterized by mild facial dysmorphysm, arthrogryposis, bent-bone dysplasia, unexplained episodes of hyperthermia, respiratory distress, and feeding and swallowing difficulties (Figure 166.2 [A] and [B]). The genetic basis for this condition is not clear.

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Figure 166.2. Stuve-Widerman syndrome. [A] Typical facial characteristics: trismus, up turned nose, small eye opening; [B] arthrogryposis of the fingers.

Bent-bone dysplastic changes involve the femur and tibia. Vertebral changes are often present (Figure 166.3).

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Figure 166.3. Stuve-Widerman syndrome. [A] Long bones are thick and short with large metaphyses (radiolucents and abnormal trabeculation); [B] poor vertebral ossification with pronounced anterior notch.

The distintion between Stuve-Widerman syndrome and Schwartz-Jampel syndrome type 1 b is difficult. The presence of radiolucent metaphyses with abnormal traveculation, and neonatal hyperthermia suggests Stuve-Widerman syndrome. Patients develop signs of dysautonomia. They may have normal intelect.

 

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Jones, 1996 Jones, 1997 Volpe, 1995 Volpe, 1995 Jones, 1997 Geidion, 1997 Di Rocco, 2003 Geidion, 1997 myotonic discharges?