[Status of lysosomal diseases amongst metabolic diseases]

Lysosomal diseases belong to the group of diseases which disturb the synthesis, catabolism or processing of complex molecules. These are the most common metabolic diseases, as they account for about one-third of all known metabolic diseases. They can be expressed as early as the intra-uterine stage of life, or appear after birth at any age, including during adulthood. They develop gradually, evolve independently of any intercurrent catabolic event and are independent of diet. Although they have long been associated with an inevitably fatal outcome, several can now be treated effectively, either by enzyme replacement therapy which increases catabolism of the overloaded substance thanks to an input of the deficient enzyme, or by drugs which reduce the synthesis of the overloaded substance.