Ichthyosis

Ichthyosis represents a diverse group of hereditary skin disorders characterized by excessively dry skin and accumulation of scale. These diseases are usually diagnosed during the first year of life. Ichthyosis vulgaris, an autosomal dominant trait, is the most common hereditary scaling disorder, affecting 1 in 250–300 people. Ocular involvement varies with the form of ichthyosis. Eyelid scaling, cicatricial ectropion, and conjunctival thickening are common. Primary corneal opacities are seen in 50% of patients with X-linked ichthyosis but are rarely seen in patients with ichthyosis vulgaris. Dots or filament-shaped opacities appear diffusely in pre–Descemet membrane or in deep stroma and become more apparent with age without affecting vision. Nodular corneal degeneration and band keratopathy have been described. Secondary corneal changes such as vascularization and scarring from severe ectropion-related exposure can develop.

Treatment for the ichthyosis spectrum is aimed at hydrating the skin and eyelids, removing scale, and slowing the turnover of epidermis, when appropriate. These disorders are not responsive to corticosteroids.

Ectodermal Dysplasia

Ectodermal dysplasia is a heterogeneous group of conditions characterized by the following:

presence of abnormalities at birth nonprogressive course

diffuse involvement of the epidermis plus at least 1 of its appendages (hair, nails, teeth, sweat glands)

various inheritance patterns

Ectodermal dysplasia is a rare hereditary condition that displays variable defects in the morphogenesis of ectodermal structures, including hair, skin, nails, and teeth. It has been observed to be a component in at least 150 distinct hereditary syndromes.

Many ocular abnormalities have been described in the ectodermal dysplasias, including sparse lashes and brows, blepharitis, ankyloblepharon, hypoplastic lacrimal ducts, diminished tear production, abnormal meibomian glands, dry conjunctivae, pterygia, corneal scarring and neovascularization, cataract, and glaucoma. The ocular surface changes may be due to limbal stem

cell deficiency.

Anhidrotic ectodermal dysplasia is characterized by hypotrichosis, anodontia, and anhidrosis. Sweating is almost completely lacking, and hyperpyrexia is a common problem in childhood. Atopic disease is often an associated finding. Ectrodactyly–ectodermal dysplasia–clefting syndrome is an association of ectodermal dysplasia, cleft lip and/or palate, and a clefting deformity of the hands and/or feet (also called lobster claw deformity).

Xeroderma Pigmentosum

Xeroderma pigmentosum is a rare, recessively transmitted disease characterized by impaired ability to repair sunlight-induced damage to DNA. During the first or second decade of life, the patient’s exposed skin develops areas of focal hyperpigmentation, atrophy, actinic keratosis, and telangiectasia —as though the patient has received a heavy dose of radiation. Later, many cutaneous neoplasms appear, including squamous cell carcinoma, basal cell carcinoma, and melanoma.

Ophthalmic manifestations include photophobia, tearing, blepharospasm, and signs and symptoms of KCS. The conjunctiva is dry and inflamed with telangiectasia and hyperpigmentation. Pingueculae and pterygia often occur. Corneal complications include exposure keratitis, ulceration, neovascularization, scarring, and even perforation. Keratoconus, band-shaped nodular corneal dystrophy, and gelatinous dystrophy have also been reported. Ocular neoplasms occur in 11% of patients, most frequently at the limbus. Squamous cell carcinoma is the most frequent histologic type, followed by basal cell carcinoma and melanoma. The eyelids can be involved, with progressive atrophy, madarosis, trichiasis, scarring, symblepharon, entropion, ectropion, and sometimes even loss of the entire lower eyelid.

Mannis MJ, Macsai MS, Huntley AC, eds. Eye and Skin Disease. Philadelphia: Lippincott-Raven; 1996:3–12, 39–44, 131–145. Sadowsky AE. Dermatologic disorders and the cornea. In: Krachmer JH, Mannis MJ, Holland EJ, eds. Cornea. 3rd ed. Vol 1.

Philadelphia: Elsevier/Mosby; 2011:749–761.

Vitamin A Deficiency

Xerosis (dryness of the conjunctiva and cornea) due to vitamin A deficiency is associated with loss of mucus production by the goblet cells. Similar changes can occur in epithelial cells of the gastrointestinal, genitourinary, and respiratory tracts. The ocular consequence is the Bitôt spot, a superficial foamy, gray triangular area on the bulbar conjunctiva that appears in the palpebral aperture (Fig 3-27). This spot consists of keratinized epithelium, inflammatory cells, debris, and Corynebacterium xerosis. These bacilli metabolize the debris, producing the foamy appearance. Prolonged vitamin A deficiency may lead to corneal ulcers and scars, and eventually diffuse corneal necrosis (keratomalacia). The World Health Organization classifies the ocular surface changes into 3 stages:

1.conjunctival xerosis, without (X1A) or with (X1B) Bitôt spots

2.corneal xerosis (X2)

3.corneal ulceration, with keratomalacia involving less than one-third (X3A) or more than onethird (X3B) of the corneal surface

Figure 3-27 Conjunctival xerosis with focal keratinization (Bitôt spot) as a result of vitamin A deficiency. (Courtesy of Vincent P.

deLuise, MD.)

Vitamin A deficiency is responsible for at least 20,000–100,000 new cases of blindness worldwide each year. At greatest risk are malnourished infants and babies born to vitamin A–deficient mothers, especially infants who have another biological stressor, such as measles or diarrhea. Superficial concurrent infections with herpes simplex, measles, or bacterial agents probably further predispose the child to keratomalacia and blindness. Although xerophthalmia usually results from low dietary intake of vitamin A, decreased absorption of vitamin A may also be responsible. When vitamin A deficiency and xerophthalmia occur in countries with a low rate of malnutrition, the condition is usually caused by unusual self-imposed dietary practices, chronic alcoholism, or lipid malabsorption (seen in cystic fibrosis, biliary cirrhosis, and bowel resection). The increase in gastric bypass surgery may lead to an increased incidence of vitamin A deficiency.

Systemic vitamin A deficiency, best characterized by keratomalacia, is a medical emergency with an untreated mortality rate of 50%. Although the administration of oral or parenteral vitamin A will address the acute manifestations of keratomalacia, these patients are usually affected by a much broader protein-energy malnutrition and should be treated with both vitamin and protein-calorie supplements. Malabsorption may prevent oral administration from being effective in patients with acute vitamin A deficiency. Maintenance of adequate corneal lubrication and prevention of secondary infection and corneal melting are essential steps in treating keratomalacia, but identification and proper treatment of the underlying causes are vital to successful clinical management of the ocular complications.

Paranjpe DR, Newton CJ, Pyott AAE, Kirkness CM. Nutritional disorders. In: Krachmer JH, Mannis MJ, Holland EJ, eds. Cornea. 3rd ed. Vol 1. Philadelphia: Elsevier/Mosby; 2011:721–732.