Pathophysiology
Neuropathology
The defining feature of ALS is the death of both upper motor neurons (located in the motor cortex of the brain) and lower motor neurons (located in the brainstem and spinal cord). In ALS with frontotemporal dementia, neurons throughout the frontal and temporal lobes of the brain die as well. The pathological hallmark of ALS is the presence of inclusion bodies (abnormal aggregations of protein) known as Bunina bodies in the cytoplasm of motor neurons. In about 97% of people with ALS, the main component of the inclusion bodies is TDP-43 protein; however, in those with SOD1 or FUS mutations, the main component of the inclusion bodies is SOD1 protein or FUS protein, respectively. The gross pathology of ALS, which are features of the disease that can be seen with the naked eye, include skeletal muscle atrophy, motor cortex atrophy, sclerosis of the corticospinal and corticobulbar tracts, thinning of the hypoglossal nerves (which control the tongue), and thinning of the anterior roots of the spinal cord. Aside from the death of motor neurons, two other characteristics common to most ALS variants are focal initial pathology, meaning that symptoms start in a single spinal cord region, and progressive continuous spread, meaning that symptoms spread to additional regions over time. Prion-like propagation of misfolded proteins from cell to cell may explain why ALS starts in one area and spreads to others. The glymphatic system may also be involved in the pathogenesis of ALS.
Subcutaneous granuloma annulare is a skin condition of unknown cause, most commonly affecting children, with girls affected twice as commonly as boys, characterized by skin lesions most often on the lower legs. : 704

See also
Granuloma annulare
Skin lesion
List of cutaneous conditions

References


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