TAY SACHS AND SANDHOFF DISEASE ARE GM2 GANGLIOSIDOSIS WHICH ARE AUTOSOMAL RECESSIVE DISORDERS. TAY SACHS DISEASE IS CAUSED DUE TO DEFICIENCY OF ENZYME HEXOSAMINIDASE A WHEREAS SANDHOFF DISEASE IS DUE TO DEFICIENCY OF ENZYME HEXOSAMINIDASE A & B. TAY SACHS DISEASE HAS 3 FORMS - INFANTILE FORM IS A FATAL NEURODEGENERATIVE DISEASE WITH MACROCEPHALY, LOSS OF MOTOR SKILLS, INCREASED STARTLE REACTION & MACULAR CHERRY RED SPOT. JUVENILE-ONSET FORM PRESENTS WITH ATAXIA & DEMENTIA WITH DEATH BY 10-15 YEARS. ADULT-ONSET FORM STARTS WITH CLUMSINESS IN CHILDHOOD; PROGRESSIVE MOTOR WEAKNESS IN ADOLESCENCE & SPINOCEREBELLAR SIGNS & DYSARTHRIA IN ADULTHOOD.

GAUCHER DISEASE IS AN AUTOSOMAL RECESSIVE LYSOSOMAL STORAGE DISEASE THAT LEADS TO ACCUMULATION OF GLUCOCEREBROSIDE IN TISSUES DUE TO DEFECTIVE ACTIVITY OF ENZYME BETA GLUCOSIDASE WITH MUTATIONS IN GBA1 GENE. ALL PATIENTS HAVE NON-UNIFORM INFILTRATION OF BONE MARROW BY GAUCHER CELLS. TYPE 1 GAUCHER DISEASE IS THE COMMONEST & IS NON-NEURONOPATHIC WHEREAS TYPES 2 & 3 ARE NEURONOPATHIC. TYPES 1 & 3 GAUCHER DISEASE CAN BE EASILY TREATED BY ENZYME REPLACEMENT THERAPY. TYPE 2 DISEASE IS RARE, SEVERE LEADING TO DEATH BY 2 YEARS OF AGE.

NIEMANN-PICK DISEASE IS AN AUTOSOMAL RECESSIVE LYSOSOMAL STORAGE DISEASE CAUSED BY DEFICIENCY OF ENZYME SPHINGOMYELINASE. IT IS OF 2 TYPES - TYPE A DISEASE MANIFESTS IN THE FIRST 6 MONTHS OF LIFE WITH RAPID PROGRESSIVE CNS DETERIORATION, HEPATOSPLENOMEGALY & FAILURE TO THRIVE. TYPE B DISEASE MANIFESTS LATER IN LIFE WITH PROGRESSIVE HEPATOSPLENOMEGALY EVENTUALLY LEADING TO CIRRHOSIS. MUTATIONS HAVE BEEN DETECTED IN NPC1 OR NPC2 GENE.