GENETIC-HETEROGENEITY IN SCHWARTZ-JAMPEL-SYNDROME - 2 FAMILIES WITH NEONATAL SCHWARTZ-JAMPEL-SYNDROME DO NOT MAP TO HUMAN-CHROMOSOME-1P34-P36.1

Schwartz-Jampel syndrome (SJS) is a rare autosomal recessive disorder characterised by the presence of myotonia with a mask-like face, skele tal dysplasia, and growth retardation. Two types have been defined by the age of manifestation of the symptoms. Linkage of Schwartz-Jampel S yndrome to human chromosome 1p34-p36.1 has been shown in families wher e probands presented during infancy or early childhood. We have invest igated two well documented families segregating severe neonatal SJS wi th microsatellite markers spanning the critical region of 1p34-36. No demonstrable linkage to chromosome 1 was found in either family sugges ting that a second locus is responsible for the sever form of neonatal Schwartz-Jampel syndrome.