Different genetic causes and types of<unk>  have different prognoses, though all are poor. The most severe forms of the disease, caused by a full deficiency in one of the affected proteins, cause death at a few years of age. If the deficiency is not complete, the prognosis is somewhat better and an affected child is expected to survive 6–7 years, and in rare cases, to their teenage years.
Leigh syndrome
Tay–Sachs disease
Maroteaux–Lamy syndrome
Coffin–Siris syndrome
Ohtahara syndrome
Nathalie syndrome
Laurence–Moon syndrome
Kosaki overgrowth syndrome