Other variants are less functional and are termed A-L and N-Z, dependent on whether they run proximal or distal to the M band. The presence of deviant bands on IEF can signify the presence of alpha-1 antitrypsin deficiency. Since the number of identified mutations has exceeded the number of letters in the alphabet, subscripts have been added to most recent discoveries in this area, as in the Pittsburgh mutation described above. As every person has two copies of the A1AT gene, a heterozygote with two different copies of the gene may have two different bands showing on electrofocusing, although heterozygote with one null mutant that abolishes expression of the gene will only show one band. In blood test results, the IEF results are notated as in PiMM, where Pi stands for protease inhibitor and "MM" is the banding pattern of that patient. Alpha-1 antitrypsin levels in the blood depend on the genotype. Some mutant forms fail to fold properly and are, thus, targeted for destruction in the proteasome, whereas others have a tendency to polymerise, being retained in the endoplasmic reticulum.
Relation to true melanoses
The condition is unrelated to true melanoses, such as Peutz–Jeghers syndrome and smokers melanosis.Peutz–Jeghers syndrome causes pigmentation of the skin and mucous surfaces with melanin, and polyps in the digestive tract. Non-colonic pseudomelanoses
Pseudomelanoses of other parts of the gastrointestinal tract have also been reported, and are of unclear relevance.Patients with colostomies can have melanosis involving the stoma, which is also of no significance. References


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