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
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
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
Figure 166.1.— Freeman-Sheldon syndrome. [A] Typical
facial characteristics; [B] distal arthrogryposis.
syndrome type 1 b
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.
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.
Figure 166.2.— Stuve-Widerman syndrome. [A] Typical
facial characteristics: trismus, up turned nose, small eye opening; [B]
arthrogryposis of the fingers.
dysplastic changes involve the femur and tibia. Vertebral changes are
often present (Figure 166.3).
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
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.