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Features Departments Information |
 Robert Sidbury, MD
Amy S. Paller, MD
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Dermatology quiz ROBERT SIDBURY, MD aFall 1999 A SIX-YEAR-OLD BOY presented to the dermatology clinic with a complaint of dry, scaling, nonpruritic skin on his legs and arms since two years of age. He had a history of asthma, but was otherwise healthy and took no medications. The scaling was worse in the winter and most noticeable on the legs. The family history was significant for a father and sister with similar, lifelong skin problems. Treatment with hydrocortisone 1% cream and Vaseline Intensive Care lotion had not been helpful. On physical examination, the child appeared well. Cutaneous examination revealed diffuse, fine, white scaling, with larger scale on the extensor aspects of the distal lower extremities bilaterally (Figure 1). There was relative sparing of the face and moderate thickening of the palms and soles. The palms were hyperlinear (Figure 2). The remainder of the exam was normal. Biopsy of lesional skin showed thickening of the stratum corneum with a decreased granular layer.   The most likely diagnosis is:
Associated findings can include:
The most appropriate initial therapy includes:
Answers: C, D, and C respectively. The ichthyoses are hereditary disorders characterized by excessive scaling of the skin. Ichthyosis vulgaris, an autosomal dominant condition, is the most commonly encountered type, occurring in up to 1% of the population.1 While the skin typically appears normal at birth, fine, branny, semi-adherent scales begin to develop during the first months to years of life, imparting a rough texture to the skin. The extremities tend to be most severely affected, often manifesting a characteristic, fine white scale. The flexural surfaces as well as the diaper region tend to be largely spared, presumably due to relatively increased local humidity.2 The face is often not involved. Palms and soles frequently show accentuation of skin lines, ie. hyperlinearity, and patients have an increased incidence of keratosis pilaris, and atopic dermatitis.3 Isolated ichthyosis vulgaris is generally asymptomatic, however, pruritus can be seen in patients with co-existing eczema. Seasonal variation is noted by many patients, with symptoms abating in the relatively humid summer months, while gradual improvement occurs in some after puberty.4 The underlying pathomechanism of ichthyosis vulgaris is unknown, however, reduced concentrations of the epidermal granular layer structural protein filaggrin likely contribute to the retention of scale.5 Diagnosis is made clinically, based on distribution, morphology, and inheritance patterns. Skin biopsies of affected areas show a thickened outer layer (stratum corneum), with variable reduction or loss of the granular layer. The differential diagnosis includes other primary ichthyotic disorders such as recessive X-linked ichthyosis, lamellar ichthyosis, epidermolytic hyperkeratosis, and congenital ichthyosiform erythroderma.6 Clinical features favoring ichthyosis vulgaris include an autosomal dominant inheritance, lack of skin findings at birth, lack of extracutaneous involvment, accentuation on the lower extremities, palmoplantar thickening, and associated atopy. X-linked recessive ichthyosis in an affected boy can be further distinguished by demonstration of increased blood levels of cholesterol sulfate, due to a sulfatase deficiency. Distinguishing xerosis, or dryness of the skin, from ichthyosis vulgaris is based on the larger size of scale and relative prominence on the lower extremitities in the latter disorder. Treatment is not curative, so the chronic nature of this disorder must be emphasized to the patient. Keratolytics and alpha-hydroxy acid-containing emollients are the mainstays of therapy. Topical corticosteroids provide no benefit in this non-inflammatory condition. Unless atopic dermatitis occurs concurrently, products such as 12% ammonium lactate lotion (Lac-Hydrin), 6% salicylic acid in a gel base (Keralyt), or 10–20% urea (Carmol 10, Carmol 20) can be used to help remove excess scale. Propylene glycol is also helpful as a hygroscopic agent, by promoting water retention in the compromised outer layer of skin. Standard emollients such as Vaseline petroleum jelly and Cetaphil cream are useful, but not as effective. Although oral retinoids such as isotretinoin or acitretin can reduce scaling, their use is not appropriate for this benign condition because of toxicity. REFERENCES 1. Paller, AS: Laboratory tests for the ichthyoses. Derm Clinics 1994;12(1):99–107. 2. Shwayder T, Ott, F: All about ichthyosis. Pediatr Clin N Amer 1991;38(4):835–857. 3. Rabinowitz LG, Esterly NB: Atopic dermatitis and ichthyosis vulgaris. Pediatr Rev 1994;15(6):220–226. 4. Wells, RS, Kerr, CB: Clinical features of autosomal dominant and sex-linked ichthyosis in an English population. Br Med J 1966;1:947–950. 5. Williams, ML: Ichthyosis: Mechanism of disease. Pediatr Dermatol 1992;9(4):365–368. 6. Esterly, NB: The ichthyosiform dermatoses. Pediatrics 1968;42:990–1004. |