Hypotonia

This chapter reviews the incidence, risk factors, genetics, recurrence risk, and epidemiology of the multiple disorders causing congenital hypotonia. The differential diagnosis of various types of hypotonic syndromes includes chromosome anomalies, metabolic myopathies, peroxisomal disorders, brain malformations, congenital lower motor neuron diseases, hypoxic ischemic encephalopathy, congenital disorders of glycosylation, and multiple congenital anomaly single gene syndromes such as Kabuki syndrome and Bohring-Opitz syndrome. Recommendations for evaluation and management include discussion of key neurologic findings in the physical exam, biochemical and other laboratory screening, targeted single gene testing, panels for clinically heterogeneous disorders and exome sequencing. The clinical consult features an infant with congenital myotonic dystrophy.