Congenital hereditary corneal dystrophy (CHED) is a form of corneal endothelial dystrophy that presents at birth. CHED was previously subclassified into two subtypes: CHED1 and CHED2. However in 2015, the International Classification of Corneal Dystrophies (IC3D) renamed the condition "CHED1" to become

posterior polymorphous corneal dystrophy Posterior polymorphous corneal dystrophy (PPCD; sometimes also ''Schlichting dystrophy'') is a type of corneal dystrophy, characterised by changes in Descemet's membrane and endothelial layer. Symptoms mainly consist of decreased vision due to ...

, and renamed the condition "CHED2" to become, simply, CHED. Consequently, the scope of this article is restricted to the condition currently referred to as ''CHED''

Signs and symptoms

CHED presents congenitally, but has a stationary course. The cornea exhibits a variable degree of clouding: from a diffuse haze, to a "ground glass" appearance, with occasional focal gray spots. The cornea thickens to between two and three times is normal thickness. Rarely, sub-epithelial

band keratopathy Band keratopathy is a corneal disease derived from the appearance of calcium on the central cornea. This is an example of metastatic calcification, which by definition, occurs in the presence of hypercalcemia. Signs and symptoms Signs and sympto ...

and elevated

intraocular pressure Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated t ...

occur. Patients have blurred vision and nystagmus, however it is rare for the condition to be associated with either epiphora or

photophobia Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of ...

with this.

Genetics

CHED exhibits autosomal recessive inheritance, with 80% of cases linked to mutations in

SLC4A11 Sodium bicarbonate transporter-like protein 11 is a protein that in humans is encoded by the ''SLC4A11'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." m ...

gene. The SLC4A11 gene encodes solute carrier family 4, sodium borate transporter, member 11.

Pathology

Histologically, the

Descemet's membrane Descemet's membrane ( or the Descemet membrane) is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen (Type IV and VIII) ...

in CHED becomes diffusely thickened and laminated. Multiple layers of basement membrane-like material appear to form on the posterior part of

. The endothelial cells are sparse - they become atrophic and degenerated, with many vacuoles. The corneal stroma becomes severely disorganised; the lamellar arrangement of the fibrils becomes disrupted.

Diagnosis

Management

Management of CHED primarily involves corneal transplantation. The age that corneal transplantation is required is variable, however, it is usually necessary fairly early in life.

References