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September 2007

Difficulties in Mutation Screening of the Plasminogen (PLG) Gene in Patients With Ligneous Conjunctivitis and Severe Hypoplasminogenemia

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Copyright 2007 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2007

Arch Ophthalmol. 2007;125(9):1303. doi:10.1001/archopht.125.9.1303-a

Leyva-Castillo et al1 described a Mexican patient with ligneous conjunctivitis. Hemostaseologic studies revealed severe hypoplasminogenemia (type I plasminogen deficiency). Mutation screening of the plasminogen (PLG) gene (chromosome 6q26) suggested a 14–base pair deletion in exon 5 of the PLG gene (deleted sequence, GAACTACTGCAGGA). However, this deletion has already been described before as the result of a methodical error: accidental coamplification of sequences of the plasminogen-related gene B (NCBI accession number AC093616.5) located on chromosome 2.2,3 Furthermore, polymerase chain reaction amplification of PLG gene exons 1, 3, 4, 5, 13, 16, and 17 may lead to “false” distinct nucleotide exchanges owing to coamplified PLG homologous genes.3 Optimizing polymerase chain reaction conditions by, for example, increasing the annealing temperature or changing the primers will probably lead to the disappearance of the alleged deletion and false nucleotide exchanges.3,4 Another method to avoid coamplification of PLG homologous genes is a long polymerase chain reaction amplification strategy as described recently.5 In conclusion, the described amplified sequences are not the PLG gene and are possibly derived from PLG-like genes (PLGL) on chromosome 2, or the PLG gene of the patient has undergone a gene conversion with apolipoprotein(a) (LPA) on chromosome 6 or PLGL on chromosome 2.

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