Arthrogryposis may result from various neuromuscular or connective tissue disorders leading to in utero hypokinesia or akinesia and the prenatal development of joint contractures. We report the case of a preterm neonate born with arthrogryposis and flaccid quadriplegia that led to the diagnosis of myopathy with muscle spindle excess. The rare and unusual histopathologic abnormality associated with the myopathy illustrated in this case has been described in only three other cases in the medical literature. The concurrence of hypertrophic cardiomyopathy, arthrogryposis, and myopathy with muscle spindle excess suggests the presence of a newly described syndrome. This case clearly demonstrates that specific prenatal ultrasonographic findings combined with the presenting clinical manifestations should promptly raise the suspicion of a neuromuscular disorder.