MedGen

A rare inflammatory optic neuropathy characterized by isolated episodes (either single or recurrent) of optic neuritis not associated with other neurological or systemic disease. Patients typically present with subacute unilateral loss of vision progressing over several days to two weeks, periocular pain and pain on eye movement (which may precede the onset of visual symptoms), light flashes on eye movement, abnormal color vision, reduced contrast sensitivity, and relative afferent pupillary defect. The optic disc appears swollen in many patients, and uveitis may be associated and can be present for years before the onset of optic neuritis. [from ORDO]

Congenital erythropoietic porphyria (CEP) is characterized in most individuals by severe cutaneous photosensitivity with blistering and increased friability of the skin over light-exposed areas. Onset in most affected individuals occurs at birth or early infancy. The first manifestation is often pink-to-dark red discoloration of the urine. Hemolytic anemia is common and can range from mild to severe, with some affected individuals requiring chronic blood transfusions. Porphyrin deposition may lead to corneal ulcers and scarring, reddish-brown discoloration of the teeth (erythrodontia), and bone loss and/or expansion of the bone marrow. The phenotypic spectrum, however, is broad and ranges from nonimmune hydrops fetalis in utero to late-onset disease with only mild cutaneous manifestations in adulthood. [from GeneReviews]

An accumulation of free radical groups in the body inadequately neutralized by antioxidants, which creates a potentially unstable and damaging cellular environment linked to tissue damage. [from HPO]

A rare stiff person syndrome spectrum disorder characterized by limb and truncal rigidity, stimulus-sensitive spasms, myoclonus, hyperekplexia, autonomic disturbance, and brainstem involvement or other neurological defects. The condition is progressive and potentially life-threatening, especially due to respiratory failure. It may be associated with the presence of glycine receptor or glutamic acid decarboxylase antibodies, as well as thymomas or lymphomas. [from ORDO]