Ichthyosis vulgaris_Follicular Plugging
An 11-year-old girl presented to the dermatology clinic complaining of “dry skin” on her shins. The condition had been present since early childhood, but its appearance had not bothered the girl until recently. Physical examination revealed fine, dry, “pasted-on” scales and follicular plugging (Figure 1) on much of her trunk and extremities. The lesions were especially notable on the dorsal forearms and shins (Figure 2). The antecubital and popliteal flexures, face, axillae, and gluteal cleft were spared. There was no pain or pruritus. The girl’s palms demonstrated accentuated skin markings, which were also seen on her mother’s hands (Figure 3). A family history revealed that the girl’s mother and grandfather had similar lesions, which decreased over time. Submit your answer, and then read the full explanation below. If you like this activity or have a suggestion, tell us about it in the comment box at the bottom of the page.Do you have related images that you would like to share? Click on the “+Image” link under the comment box to upload your photos. By submitting your photo, you agree that the patient in the photo is not identifiable or has signed a waiver in compliance with HIPAA regulations.
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This young girl was diagnosed with ichthyosis vulgaris (which literally translates to “common fish skin”), an autosomal dominant disorder. The most common of the hereditary scaling disorders, ichthyosis vulgaris affects one in every 250 to 300 people.
The condition manifests in the first year of life, usually after three months of age, as very dry skin, with the appearance of fine, “pasted-on” scales. These are particularly coarse on the lower extremities, with extensor surfaces being most severely affected.
Ichthyosis vulgaris is caused by a deficiency of filaggrin, the protein that helps keratin filaments aggregate. In patients without ichthyosis vulgaris, filaggrin is broken down into osmotically active amino acids, which maintain stratum corneum hydration. Normal swelling and shrinking cause these superficial layers of dead skin cells to slough.
Patients with ichthyosis vulgaris lack these amino acids, which prevents the normal swelling and sloughing. As a result, patients retain layers of dead skin, which manifest as fine, adherent scales and follicular plugs.
Many patients with ichthyosis vulgaris also present with atopic dermatitis. Unlike ichthyosis vulgaris lesions, atopic dermatitis lesions are usually inflammatory or pruritic. Other common comorbidities are keratosis pilaris, which affects 80%, and increased or accentuated palmoplantar creases in 74% of patients. Disease manifestations improve as patients reach adulthood.
Half of offspring born to a parent with ichthyosis vulgaris will be affected. However, skin changes are highly variable from person to person. Phenotype varies greatly with ambient humidity. Patients in tropical climates may have few to no noticeable abnormalities, while those in dry climates have more severe disease manifestations.
Differential diagnoses include X-linked ichthyosis, severe xerosis and acquired ichthyosis.
X-linked ichthyosis is the most difficult diagnosis to make clinically. This condition is found only in males, affecting one in every 2,000 to 5,000. Large, dark scales present on the anterior neck, extensor surfaces of the extremities and trunk. The neck’s of patients with X-lined icthyosis have a characteristic dirty or unwashed appearance, whereas only nine percent of ichthyosis vulgaris patients have neck involvement. X-linked ichthyosis is the only form of ichthyosis that spares the palms and soles; flexures are spared in 70% of these patients.
The extent and severity of X-linked icthyosis increases with age. Diagnosis is based on a blood test for cholesterol sulfate or lipoprotein electrophoresis. Effective treatments include ammonium lactate, calcipotriol ointment and cholesterol cream 10%.
Severe xerosis leads to asteatotic eczema (also known as “xerotic eczema”) and eczema craquelé. Unlike ichthyosis, xerosis is caused by environmental factors and worsens with age.
Severe xerosis patients are typically elderly; present during dry, northern winter months; and have a history of frequent, lengthy baths and heavy soap use. Low humidity in overheated rooms contributes to the condition.
Severe xerosis presents as dry, scaly skin, especially on extensor surfaces of the legs. Eczematous patches on the pretibial area may develop fine cracks or fissures. The face, scalp, groin and axillae are spared. Severe cases can be clinically indistinguishable from ichthyosis vulgaris.
Treatment for severe xerosis includes removal of the inciting causes and use of lubricants, such as ammonium lactate (Lac-Hydrin) 12% cream. Bland moisturizers help eliminate redness and itching.
Acquired ichthyosis is rare and develops secondary to a systemic disease. Symptoms resemble ichthyosis vulgaris, but onset is usually rapid and occurs during adulthood. This condition has been associated with Hodgkin’s disease, mycosis fungoides and multiple myeloma. Implicated medications include nicotinic acid, triparanol and butyrophenones.
Moisturizing keratolytics, such as tretinoin topical (Retin-A, Avita) or tazarotene (Tazorac), are the most effective treatment for ichthyosis vulgaris.
Ammonium lactate 12% cream or lotion applied twice daily, especially after bathing, leads to dramatic improvement, as it did with the patient in this case. If atopic dermatitis coexists, applying a topical corticosteroid before ammonium lactate will eliminate burning.
Thomas W. McGovern, MD, is a Mohs surgeon and general dermatologist with Fort Wayne Dermatology in Fort Wayne, Ind.
1. Odom RB, James WD, Berger TG, eds. Andrews’ Diseases of the Skin: Clinical Dermatology. 9th ed. WB Saunders; Philadelphia: 2000:52, 701, 709.
2. Bale SJ, Doyle SZ. The genetics of ichthyosis: a primer for epidemiologists. J Invest Dermatol. 1994;49S:102.