Résumé :
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Type IV Glycogen storage disease is a rare hereditary metabolic disorder, which is due to the absence of the glycogen branching enzyme amylo-1,4-1,6 transglucosidase, critical in the production of glycogen. This leads to very long unbranched glucose chains being stored in glycogen. The long unbranched molecules (known as amylose) have a low solubility which leads to precipitation. These deposits subsequently build up in body tissue, especially the heart and liver, but also muscle and brain. Depending on the age, the clinical features differ. Regarding the tissue involved by storage: very rare perinatal form (neonatal severe encephalopathy) with diffuse tissue involvement, ( brain, muscle, liver, heart) ; infantile onset form with hepatospenomegaly, progressive cirrhosis and chronic hepatic failure (the most common type also known as Andersen's disease) ; infantile onset form with muscle , heart and motor neurons involvement ; juvenile form with cardiomyopathy ; adult polyglucosan body disease , most commonly seen in patients of Ashkenaszi Jewish lineage with progressive distal sensorimotor neuropathy and mild dementia. (depositions of polyglucosan bodies are present in both the CNS and in the peripheral nerve, but not in muscle).We report two cases of glycogen storage type IV disease, one with fetal onset, the secund with infantile, both with unsual features.Case 1 was a fetus stillborn at 32GW from unrelated parents. Two weeks before birth , fetal movements progressely decrease as an hydramnios appeared. Intra-uterine death occurred. Autopsy findings revealed a fetal hydrops with hepatosplenomegaly and distal joints fixation. At histological level, a broad PAS(+) storage involved liver, muscle, heart and brain cells. At the ultrastructural level , the storage displayed the characteristic aspect of branched filaments. Case 2 was a 30 months old boy that initially presented with a delayed motor development and then with proximal weakness. At 15 months, an isolated increase of liver enzymes was noted, followed 9 months later by the appearance of a discrete but progressive hepatosplenomegaly. Heart explorations were normal as were neurological evaluations. Muscle biopsy revealed a glycogene storage. Maltase acid level were normal whereas glycogen branching enzyme was deficient. Our reports illustrate the wide clinical spectrum of the glycogen storage type IV disease as the differences in tissue involvement.
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