What is unusual about the genetically-inherited mitochondrial disease LHON as compared to the genetically-inherited disease sickle cell anemia?

LHON (Leber Hereditary Optic Neuropathy) : Is a disease that is characterized by loss of vision in young adults.

Sickle cell anemia: Is a disease characterized by production of abnormally shaped red blood cells, that is, not round in shape as normal but are 'sickle' shaped or elongated/crescent shaped.

Both diseases are heritable But LHON is caused by mutations existing in the mitochondrion thus only inherited maternally.

Sickle cell anemia is caused by mutations in the HBB gene which produces the beta subunit of hemoglobin. It is inherited from recessive genes of both parents.