Ligneous conjunctivitis and use of human plasminogen eyedrops: The Italian experience

Type I congenital plasminogen (PLG) deficiency (PLGD-I), also called hypoplasminogenemia, is an ultrarare autosomal-recessive systemic disorder1–4 with an estimated prevalence of ∼1.6/million. It is characterized by uncontrolled growth of fibrin-rich, woody (ligneous) pseudomembranous lesions on mucous membranes in different body sites that may be life threatening. The disorder is caused by homozygous or compound-heterozygous mutations in the PLG gene resulting in a quantitative PLGD-I (low plasminogen antigen and activity levels).5 The degree of reduction of the PLGplasma level is variable,with a PLGactivity ranged from 4%to 51% (normal range 75%–120%).6 Interestingly, patients that are more clinically severe affected do not necessarily present the lowest PLGactivity levels and often their family memberswith activity levels less than 50% do not show clinical signs of the disease. The reasons for the lack of correlation between laboratory and clinical phenotype and contributing factors for differential expressivity of specific alleles, which also occurs within the same family, have not been clearly elucidated.5,6 They may be due to unidentified modifier genes or epigenetic factors and should be further investigated.