Granular corneal dystrophy  is a slowly progressive corneal dystrophy that most often begins in early childhood. Granular corneal dystrophy has two types:

Granular corneal dystrophy type I, also corneal dystrophy Groenouw type I, is a rare form of human corneal dystrophy. It was first described by German ophthalmologist Arthur Groenouw in 1890. Granular corneal dystrophy type II, also called Avellino corneal dystrophy or combined granular-lattice corneal dystrophy is also a rare form of corneal dystrophy. The disorder was first described by Folberg et al. in 1988. The name Avellino corneal dystrophy comes from the first four patients in the original study each tracing their family origin to the Italian province of Avellino. Presentation
Granular corneal dystrophy is diagnosed during an eye examination by an ophthalmologist or optometrist. The lesions consist of central, fine, whitish granular lesions in the cornea. Visual acuity is slightly reduced. Genetics
Granular corneal dystrophy is caused by a mutation in the TGFBI gene, located on chromosome 5q31. The disorder is inherited in an autosomal dominant manner. This indicates that the defective gene responsible for the disorder is located on an autosome (chromosome 5 is an autosome), and only one copy of the gene is sufficient to cause the disorder, when inherited from a parent who has the disorder. The gene TGFBI encodes the protein keratoepithelin. Diagnosis
Treatment
Corneal transplant is not needed except in very severe and late cases. Light sensitivity may be overcome by wearing tinted glasses. See also
Corneal dystrophy


== References ==
The growth rates of benign and malignant tumors also differ; benign tumors generally grow more slowly than malignant tumors. Although benign tumors pose a lower health risk than malignant tumors, they both can be life-threatening in certain situations. There are many general characteristics which apply to either benign or malignant tumors, but sometimes one type may show characteristics of the other. For example, benign tumors are mostly well differentiated and malignant tumors are often undifferentiated. However, undifferentiated benign tumors and differentiated malignant tumors can occur. Although benign tumors generally grow slowly, cases of fast-growing benign tumors have also been documented. Some malignant tumors are mostly non-metastatic such as in the case of basal-cell carcinoma. CT and chest radiography can be a useful diagnostic exam in visualizing a benign tumor and differentiating it from a malignant tumor. The smaller the tumor on a radiograph the more likely it is to be benign as 80% of lung nodules less than 2 cm in diameter are benign. Most benign nodules are smoothed radiopaque densities with clear margins but these are not exclusive signs of benign tumors. Multistage carcinogenesis
Tumors are formed by carcinogenesis, a process in which cellular alterations lead to the formation of cancer. Multistage carcinogenesis involves the sequential genetic or epigenetic changes to a cells DNA, where each step produces a more advanced tumor. It is often broken down into three stages; initiation, promotion and progression, and several mutations may occur at each stage. Initiation is where the first genetic mutation occurs in a cell.