The importance of functionally active TPPI is evident from a debilitating neurodegenerative disorder called the classic late-infantile neuronal ceroid lipofuscinosis (LINCL, OMIM 204500), also known as neuronal ceroid lipofuscinosis 2 or Jansky-Bielschowsky disease [4], [5]. The gene discussed is TPP1; the disease is late infantile neuronal ceroid lipofuscinosis.