Myopathy with muscle spindle excess: A new congenital neuromuscular syndrome?

An infant presented with congenital weakness, hypotonia, arthrogryposis, at rial tachycardia, and a left intra-abdominal neuroblastoma. Muscle biopsy r evealed marked excess of muscle spindles with atrophy of extrafusal fibers. The patient expired at age 14 months from progressive cardiorespiratory fa ilure. Postmortem examination demonstrated muscle-spindle excess in other m uscles, along with hypertrophic obstructive cardiomyopathy and organomegaly . Muscle spindle excess has previously been reported in two patients with N oonan syndrome and progressive hypertrophic cardiomyopathy. Muscle spindle excess with hypertrophic cardiomyopathy, organomegaly, and, possibly, conge nital neuroblastoma suggests a syndromic association and may represent an u nusual form of congenital myopathy. (C) 2001 John Wiley & Sons, Inc.