Three related patients are described with glycogenosis type IV with an
unusual clinical presentation resulting in perinatal death. Stored ma
terial showed birefringent Maltese crosses and was present in skeletal
muscles, heart, central nervous system, and liver. Muscular dysfuncti
on resulted in a fetal hypokinesia sequence with arthrogryposis and lu
ng hypoplasia. A subdivision of glycogenosis type IV in four subtypes
is proposed, based on age of onset. Measurement of the enzyme activiti
es in different tissues does not permit, at the moment, a distinction
between the subtypes.