All are lysosomal storage disorders except -

Ans. is 'c' i.e., Me Ardle's Disease* Lysosomal storage disorders is a group of metabolic disorders caused by a defect of lysosome. Lysosomes are sacs concerned with metabolising unwanted lipids, glycoproteins and mucopolysaccharides.* They are classified as# Lipid storage disorders* E.g., sphingolipidosis like Gml gangliosidosis caused by b galactosidase defect, GM2 gangliosidoses caused by hexosaminidase A defect, Fabry's disease caused by a galactosidase defect, Gaucher's disease caused by b glucosidase defect, Farber's disease caused by ceramidase defect (It is a granulomatous condition and it presents with painful subcutaneous nodules, hepatosplenomegaly and pulmonary involvement)# Mucopolysaccharidoses* E.g., Hurler syndrome caused by a defect of L-iduronidase, Hunter syndrome caused by a defect of L-iduronate sulfatase.# Glycoprotein storage disorders* E.g., Fucosidosis, Mannosidosis# Mucolipidosis* E.g., I cell disease - caused by a defect of GlcNAC phosphotransferase. Because of this defect, the lysosomal enzymes are not labelled with mannose 6 phosphate. Mannose 6 phosphate is required as a label for targeting lysosomal enzymes to lysosomes. In this condition, lysosomal enzymes do not reach lysosomes. They are secreted out. Lysosomes are empty bags. Hence all undigested glycoproteins and lipids accumulate within all cells as Inclusions, that is why the name I cell disease or Inclusion cell disease. This condition resembles hurler syndrome# Apart from this classification, there is also lysosomal transporter defects like cystinosis caused by a defect of efflux of cysteine from lysosomes. It is characterised by fanconi's syndrome, photophobia and characteristic cysteine crystals can be observed in cornea on slit lamp examination# All these disorders are autosomal recessive disorders except Hunter syndrome and Fabry's disease, both of which are X linked recessive disorders.# All lysosomal storage disorders present as hepatosplenomegaly, mental retardation, seizures with or without deafness and blindness.# Me Ardle's disease is not a lysosomal storage disorder. It is Glycogen Storage Disorder Type V (GSDIV). It is caused by Muscle Glycogen phosphorylase defect. It presents as exercise intolerance, intolerance to anaerobic exercises. Glycogen phosphorylase is not a lysosomal enzyme, it is a cytoplasmic enzyme.# The only Glycogen storage disorder which is also a Lysosomal Storage disorder is Type IIGSD or Pompe's disease, caused by alpha glucosidase defect.