Here I present: “Ligneous Conjunctivitis”, Victor McKusick, Mendelian Inheritance in Man’, 1966.
INTRODUCTION.
Ligneous conjunctivitis is a form of chronic conjunctivitis characterized by recurrent, fibrin-rich pseudomembranous lesions of wood-like consistency that develop mainly on the underside of the eyelid (tarsal conjunctiva). It is generally a systemic disease which may involve the periodontal tissue, the upper and lower respiratory tract, kidneys, middle ear, and female genitalia. It can be sight-threatening, and death can occasionally occur from pulmonary involvement.
The PLG gene encodes plasminogen, a circulating zymogen that is converted to the active enzyme plasmin by cleavage of the peptide bond between arg560 and val561, which is mediated by urokinase and tissue plasminogen activator The main function of plasmin is to dissolve fibrin clots. Plasmin, like trypsin, belongs to the family of serine proteinases. Besides its importance in the fibrinolytic system, PLG is implicated in multiple other biologic processes, including cell migration, degradation of the extracellular matrix, and tissue remodeling.
Ligneous conjunctivitis is usually the initial and most common manifestation of type-I congenital plasminogen deficiency. There is evidence that type-I plasminogen deficiency is caused by homozygous or compound heterozygous mutation in the gene encoding plasminogen (PLG) on cytogenetic location 6q26 and genomic coordinates 6:160,702,193-160,754,097. The screenshot of the PLG gene 51,905 bp (base pairs) of DNA sequence length is shown BELOW. Nine (9) other genes besides PLG in the 6q26 cytogenetic location are listed BENEATH.
| Coordinate | Symbol | Genomic Name |
| 6:160,466,555 | LPAL2 | Lipoprotein(a)-like 2 |
| 6:160,531,482 | LPA | Apolipoprotein Lp(a) |
| 6:160,600,001 | DFNB38 | Deafness, autosomal recessive 38 |
| 6:160,600,001 | MRT28 | Intellectual developmental disorder, recessive 28 |
| 6:160,702,193 | PLG | Plasminogen |
| 6:160,991,769 | MAP3K4 | Mitogen-activated protein kinase kinase kinase 4 |
| 6:161,129,967 | AGPAT4 | 1-acylglycerol-3-phosphate O-acyltransferase 4 |
| 6:161,347,417 | PRKN | Parkin RBR E3 ubiquitin protein ligase |
| 6:162,727,132 | PACRG | Parkin coregulated gene |
| 6:163,413,065 | CAHM | Colorectal adenocarcinoma hypermethylated gene |
