Lebers hereditary optic neuropathy (LHON) is a mitochondrially inherited (transmitted from mother to offspring) degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; it predominantly affects young adult males. LHON is  transmitted only through the mother, as it is primarily due to mutations in the mitochondrial (not nuclear) genome, and only the egg contributes mitochondria to the embryo. LHON is usually due to one of three pathogenic mitochondrial DNA (mtDNA) point mutations. These mutations are at nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit genes of complex I of the oxidative phosphorylation chain in mitochondria. Men cannot pass on the disease to their offspring. Signs and symptoms
Clinically, there is an acute onset of visual loss, first in one eye, and then a few weeks to months later in the other. Onset is usually young adulthood, but age range at onset from 7-75 is reported. The age of onset is slightly higher in females (range 19–55 years: mean 31.3 years) than males (range 15–53 years: mean 24.3). The male-to-female ratio varies between mutations: 3:1 for 3460 G>A, 6:1 for 11778 G>A and 8:1 for 14484 T>C.This typically evolves to very severe optic atrophy and a permanent decrease of visual acuity. Both eyes become affected either simultaneously (25% of cases) or sequentially (75% of cases) with a median inter-eye delay of 8 weeks. Rarely, only one eye is affected.
Deformability of the erythrocytes that cause the microcirculatory distress can be demonstrated through various other hemorheological characteristics. In order to determine the deformability of erythrocytes multiple factors including blood and plasma viscosity and hematocrit (a calculation of the percent of red blood cells present in the blood) are measured. Alpha-thalassemia
Alpha-thalassemia, like sickle cell trait, is typically inherited in areas with increased exposure to malaria. It manifests itself as a decreased expression of alpha-globin chains, causing an imbalance and excess of beta-globin chains, and can occasionally result in anemic symptoms. The abnormal hemoglobin can cause the body to destroy red blood cells, essentially causing anemia.In endurance-trained individuals with sickle cell trait the presence of alpha-thalassemia has been shown to act protectively against microvasculatory distress before, during, and after exercise. Signs, symptoms, and prevention
Because of the microcirculatory distress, a telltale sign or symptom of a potential sickling collapse is cramping. Specifically to sickle cell trait, cramping occurs in the lower extremities and back in athletes undergoing intense physical activity or exertion. In comparison to heat cramps, sickling cramps are less intense in terms of pain and have a weakness and fatigue associated with them, as opposed to tightly contracted muscles that lock up during heat cramps.A sickling collapse comes on slowly, following cramps, weakness, general body aches and fatigue.