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Disorders of Keratinization

»	What are the ichthyosiform dermatoses?
»	What does “ichthyosis” mean?
»	How common are the congenital ichthyoses? How are they inherited?
»	What features help differentiate the most common inherited ichthyoses?
»	What genetic defect is responsible for X-linked ichthyosis (XLI)?
»	What additional phenotypes may patients with XLI contiguous gene syndromes exhibit?
»	What important birth history may be obtained in patients with XLI?
»	Name the hereditary syndromes presenting with ichthyosis as a component.What is a collodion baby?
»	What is a harlequin fetus?
»	Name several conditions associated with acquired ichthyosis.
»	Are laboratory tests helpful in the diagnosis of ichthyoses?
»	Is prenatal diagnosis of congenital ichthyosis possible?
»	How is ichthyosis treated?
»	What is Hailey-Hailey disease?
»	How does Hailey-Hailey disease present?
»	Do any factors exacerbate the skin changes of Hailey-Hailey?
»	Which diseases may be confused with Hailey-Hailey disease?
»	How is Hailey-Hailey disease treated?
»	What is Darier’s disease?
»	How is Darier’s disease diagnosed?
»	Are there any nail or hair changes in Darier’s disease?
»	Is Darier’s disease difficult to treat?
»	What is a collodion baby?

Name several conditions associated with acquired ichthyosis.

See Table 4-3.

Table 4-3. Conditions Associated with Acquired Ichthyosis
	MEDICATIONS	MALIGNANCIES	NUTRITIONAL DISORDERS	METABOLIC DISORDERS	MISCELLANEOUS DISORDERS
	Butyrophenone Cimetidine Clofazimine Dixyrazine Isoniazid Nafoxidine Niacin Triparanol Allopurinol Retinoids	Non–Hodgkin’s lymphoma Hodgkin’s lymphoma Carcinoma of solid organs Mycosis fungoides Leukemia Lymphosarcoma Rhabdomyosarcoma Kaposi’s sarcoma Leiomyosarcoma Multiple myeloma	Essential fatty acid deficiencies Hypervitaminosis A Hypovitaminosis A Kwashiorkor Pellagra	Chronic renal failure Hypothyroidism Panhypopituitarism	Systemic lupus erythematosus Sarcoidosis Leprosy Dermatomyositis HIV infection Polycythemia Haber’s syndrome

Fig. 4.3 Acquired ichthyosis due to clofazimine. (Courtesy of the Fitzsimons Army Medical Center teaching files.)

Malignancy: The pathogenesis of the skin changes associated with malignancies is unknown, although reduced dermal lipid synthesis, malabsorption, and immunologic abnormalities have been identified.

Nutritional and metabolic disorders: Many of nutritional problems involve abnormal vitamin A metabolism. Chronic renal failure may result in hypervitaminosis A, which produces rough, scaly skin. Hypovitaminosis A produces follicular hyperkeratosis and dry skin.

Drugs and other therapies: Medications produce ichthyosis by various mechanisms. Niacin, triparanol, butyrophenones, dixyrazine, and nafoxidine alter cholesterol synthesis. Cimetidine and retinoids are antiandrogenic and reduce sebum secretion (Fig. 4-3).
Homayoun A: Acquired ichthyosis and related conditions, Int J Dermatol 23:458–461, 1984.