In addition, it may occur in other parts of the body in some people treated for inflammatory skin diseases with phototherapy.The rash is usually quite symmetrical and characteristic for each individual, appearing similar with each recurrence, but can look dissimilar in different people.Fever, fatigue and headaches have been previously associated with the eruption, but are rare.The rash may persist for many days to a couple of weeks, resolving spontaneously without scarring as long as further sunlight exposure is avoided.Recurring yearly, the eruption can sometimes last longer than a few days if persistent and repeated sun exposure occurs. However, the "hardening" effect, with respite during the later summer, frequently occurs with gradual exposure of sunlight, eventually leading to significant improvement. Causes
The cause of PLE is not yet understood, but several factors may be involved. It is thought to be due to a type IV delayed-type hypersensitivity to an allergen produced in the body following sunlight exposure, in a genetically susceptible person. It is also thought that skin microbiome or microbial elements could be involved in pathogenesis of the disease

UV exposure
PLE can be provoked by UVA or UVB (chief cause of sunburn) rays, meaning it can be triggered even by sunlight through glass. UV-A is a major constituent of sunlight, can pass through glass, is relatively resistant to sunscreen and can cause light eruption without sunburn.Artificial UV light sources from tanning units and phototherapy treatment units can also trigger PLE.
Mycobacterium avium complex is a group of mycobacteria comprising Mycobacterium intracellulare and Mycobacterium avium that are commonly grouped because they infect humans together; this group, in turn, is part of the group of nontuberculous mycobacteria. These bacteria cause Mycobacterium avium-intracellulare infections or Mycobacterium avium complex infections in humans. These bacteria are common and are found in fresh and salt water, in household dust and in soil. MAC bacteria usually cause infection in those who are immunocompromised or those with severe lung disease. Description
In the Runyon classification, both bacteria are nonchromogens. They can be differentiated from M. tuberculosis and each other by commercially available DNA probes. : 245 They are characterized as Gram-positive, nonmotile, acid-fast, short to long rods. Colony characteristics

Usually, colonies are smooth, rarely rough, and not pigmented colonies. Older colonies may become yellow.Physiology

Growth on Löwenstein-Jensen medium and Middlebrook 7H10 agar occurs at 37°C after seven or more days. The complex can be (but is not often) resistant to isoniazid, ethambutol, rifampin, and streptomycin.Differential characteristics

M. intracellulare and M. avium form the M. avium complex (MAC). Remarkable ITS heterogeneity is seen within different M. intracellulare isolates. Type strains
M. intracellulare type strains include ATCC 13950, CCUG 28005, CIP 104243, DSM 43223, JCM 6384, and NCTC 13025.M. avium type strains include ATCC 25291, DSM 44156, and TMC 724. Human health
MAC bacteria enter most peoples body when inhaled into the lungs or swallowed, but only cause infection in those who are immunocompromised or who have severe lung disease such as those with cystic fibrosis or chronic obstructive lung disease (COPD).