Dry, Scaly Skin in a Young Boy

Ichthyoses are a group of genetic skin disorders that share the common feature of the appearance of scaly skin, which has frequently been likened to fish scales (ichthys meaning "fish" in Greek). Although many variants exist, most appear early in...

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Ichthyoses are a group of genetic skin disorders that share the common feature of the appearance of scaly skin, which has frequently been likened to fish scales (ichthys meaning “fish” in Greek). Although many variants exist, most appear early in infancy or childhood with only rare cases presenting for the first time in adulthood. Ichthyoses vary widely in appearance, from mild hyperkeratosis to severe hyperkeratosis with bullae. Some forms of ichthyoses, such as harlequin-type ichthyosis, are often fatal in early infancy due to severe dehydration and respiratory failure as the chest fails to expand. Most of the more common ichthyoses variants, however, can be managed with only minor lifestyle modifications and a set skin care regimen. The most common form of ichthyosis is known as ichthyosis vulgaris (IV).^1,2

Similar to the majority of the other forms of ichthyoses, IV generally presents in infants, with the most common age of initial presentation at 3 to 5 months. IV occurs in about 1 in 250 to 1 in 1000 cases with varying degrees of severity.² IV is characterized by extremely xerotic skin, scaling, and occasional eczema and pruritus. Often patients will bleed as a result of cracks in the skin secondary to disease. These cracks allow for excess loss of moisture from the skin surface, which further exacerbates the lesions.¹ 

The etiology of the lesions seen in IV is primarily genetic. Specifically, IV results from a mutation in the FLG gene, which encodes for the protein profilaggrin. Profilaggrin is the precursor to filaggrin, a cross-linking protein in the stratum corneum that helps to form an insoluble barrier against epidermal water loss and environmental insults. The genetic mutation present in IV leads to the loss of the epidermal integrity resulting in the appearance of scaly, cracked skin.^2,3 Although IV is generally considered to be inherited in an autosomal dominant fashion, mutations in a single copy of FLG seem to result in much milder forms of IV compared to when both copies are mutated.³ Thus, it is possible that IV resulting from FLG mutations displays incomplete expression in humans.⁴ Apart from the underlying genetic factors that lead to the development of IV, multiple environmental factors contribute to the disease course as well. Factors that have been shown to worsen the severity of IV include exposure to cold temperatures, dry climate, and poor skin moisturization.^1,4 In addition to exacerbating existing IV, these factors can also trigger the recurrence of this condition in adults who may have experienced it as infants.

In a majority of cases, the diagnosis of IV can often be made based on the gross appearance of the skin and historical information, particularly a family history of disease, obtained from the patient. If the diagnosis is uncertain, a biopsy of the skin may be performed, which would show hyperkeratosis of the stratum corneum and hypoplasia of the stratum granulosum with a normal dermis.⁴

When considering a diagnosis of IV, the differential should include the multiple different types of ichthyoses, which may have a similar presentation to that of IV. X-linked ichthyosis is the closest in presentation to IV, as it also appears as scaling of the skin in similar body regions and also primarily occurs during infancy. X-linked ichthyosis is due to a mutation in the gene encoding steroid sulfatase (STS) found on the X chromosome. The identification of this mutation can be used to differentiate X-linked ichthyosis from IV. These two diagnoses can be further differentiated via biopsy examination, which will show a normal stratum granulosum in X-linked ichthyosis as opposed to the diminished stratum granulosum seen in IV.⁵ Other disorders to consider on the differential include lamellar ichthyosis, epidermolytic hyperkeratosis, and xerotic dermatitis. Typically, lamellar ichthyosis presents with a thicker, darkened stratum corneum and an increased stratum granulosum, secondary to transglutaminase ¹ mutations.⁶ Epidermolytic hyperkeratosis is another disease that can present with the same hyperkeratosis as seen IV; however, epidermolytic hyperkeratosis is usually accompanied by the formation of bullae as a result of destruction of the cells in the stratum granulosum that arises due to collagen VII mutations.⁷ Furthermore, xerotic dermatitis can be differentiated from IV based on the age at initial presentation, as xerotic dermatitis often has onsets later in life.⁸

Currently, there is no definitive treatment for IV that serves to cure the disease. Instead, treatment focuses on preserving epidermal integrity and minimizing the evaporation of water from the surface of the skin. Thick moisturizers and topical medications with 10% lactic acid (eg, AmLactin) or 10% urea (eg, Ureacin-10) have proven to be helpful in the management of disease.³ Additionally, maintaining a warm, moist environment has also proven to be beneficial in controlling this condition.¹

In this case, the patient’s parents were educated regarding the typical course of IV and the steps that could be taken to manage their son’s disease. They were instructed to moisturize the affected areas and apply a 10% lactic acid lotion daily to the affected areas. The parents were also advised to avoid dry, cold weather, and to be hyper-vigilant about applying moisturizers in situations in which these conditions could not be avoided.

Daniel Colchado, BA, is a medical student, Joan Fernandez, BS, is a medical student, and Christopher Rizk, MD, is a dermatology resident at the Baylor College of Medicine in Houston. 

References

1. Takeichi T, Akiyama M. Inherited ichthyosis: non‐syndromic forms. J Dermatol. 2016;43:242-251.
2. Traupe H, Fischer J, Oji V. Nonsyndromic types of ichthyoses—an update. 
3. J Dtsch Dermatol Ges. 2014;12:109-121.
4. Smith FJ, Irvine AD, Terron-Kwiatkowski A, et al. Loss-of-function mutations in the gene encoding filaggrin cause ichthyosis vulgaris. Nat Genet. 2006;38:337-342.
5. Monahan TP, Cohen BA, Siegfried EC. Congenital and hereditary disorders of the skin. In: Avery’s Diseases of the Newborn. 8th ed. Philadelphia: Elsevier; 2004:1483-1502.
6. Hand JL, Runke CK, Hodge JC. The phenotype spectrum of X-linked ichthyosis identified by chromosomal microarray. J Am Acad Dermatol. 2015;72:617-627.
7. Elias PM, Schmuth M, Uchida Y, et al. Basis for the permeability barrier abnormality in lamellar ichthyosis. Exp Dermatol. 2002;11:248-256.
8. Hernández-Martín A, Cuadrado-Corrales N, Ciria-Abad S, et al. X-linked ichthyosis along with recessive dystrophic epidermolysis bullosa Palmer CN, Irvine AD, Terron-Kwiatkowski A, et al. Common loss-of-function variants of the epidermal barrier protein filaggrin are a major predisposing factor for atopic dermatitis. Nat Genet. 2006;38:441-446.