Skeletal muscle involvement in Escobar syndrome.

In addition to the clinical characteristics of Escobar syndrome, including an anomalous facial expression, multiple joint contractures, multiple pterygia and a short stature, two female siblings developed proximal dominant muscle weakness from birth and slowly progressive scoliosis. Biopsied specimens obtained from the paravertebral and gluteus maximums muscles at the time of spinal surgery showed variation in fiber size, increased numbers of fibers with central nuclei, interstitial fibrosis and disorganized intermyofibrillar networks with occasional core/targetoid formations. The most outstanding histochemical abnormality in both cases was an abnormal fiber type distribution (type 2 fiber deficiency) which might be the result of an abnormal or deficient neural supply to the developing muscles. The defective neural influence on the muscle is assumed to produce the above-mentioned muscle changes, inducing multiple joint contractures and scoliosis.