History
Hereditary ichthyosis
Although the skin in hereditary ichthyosis vulgaris looks and feels normal at birth, it gradually becomes rough and dry in early childhood. Scaling tends to be most prominent on the extensor surfaces of the extremities and absent on the flexor surfaces.
The diaper area is usually unaffected. The forehead and cheeks may be involved early on, but scaling usually diminishes in these areas with age. A notable amelioration of symptoms occurs during the summer months.
A family history of hereditary ichthyosis vulgaris may be difficult to ascertain because of the varying degrees of penetrance and the general improvement of symptoms over time.
Many hereditary ichthyosis vulgaris patients have associated atopic manifestations (eg, asthma, eczema, hay fever). Atopic conditions can be found in many family members, with or without symptoms of ichthyosis vulgaris. One study noted atopic manifestations in almost half of all subjects enrolled, with 41% having at least one relative who also was affected.
Acquired ichthyosis
Acquired ichthyosis is clinically indistinguishable from hereditary ichthyosis; however, acquired ichthyosis is associated with various systemic diseases.
The appearance of ichthyosis in adulthood can occur before or after the diagnosis of a systemic condition. Disease severity varies depending on the course of the associated systemic condition.
Acquired ichthyosis is associated with many systemic diseases, including cancer (especially lymphoma), primary cutaneous CD30+ lymphoproliferative disorders, [25] and other neoplasms including osseous hemangiopericytoma, [26] sarcoidosis, leprosy, thyroid disease, hyperparathyroidism, [27] nutritional disorders, chronic renal failure, bone marrow transplantation, [28] and HIV infection. [29] Autoimmune diseases, including systemic lupus erythematosus [30] and dermatomyositis, [31] are also linked. It was recently described in a patient with the overlap syndrome consisting of systemic sclerosis and systemic lupus erythematosus. [30]
The types of cancers most often found in association with acquired ichthyosis are Hodgkin disease, non-Hodgkin lymphoma (including mycosis fungoides), myeloma, Kaposi sarcoma, leiomyosarcoma, and carcinomas of the lung, breast, ovary, [32] and cervix. [33]
The use of certain medications has been linked to acquired ichthyosis, namely nicotinic acid, [34, 35] triparanol, butyrophenones, dixyrazine, [36] cimetidine, and clofazimine. [37]
Bathing suit ichthyosis is a striking and unique clinical form of autosomal recessive congenital ichthyosis characterized by marked scaling on the bathing suit areas but sparing of the extremities and the central face. Bathing suit ichthyosis, caused by transglutaminase-1 deficiency, displays evidence that suggests it is a temperature-sensitive phenotype. [38]
Physical Examination
Ichthyosis vulgaris (both hereditary and acquired) is characterized by symmetrical scaling of the skin, which varies from barely visible roughness and dryness to strong horny plates. Note the image below.
Scales are small, fine, irregular, and polygonal in shape, often curling up at the edges to give the skin a rough feel. Scales vary in size from 1 mm to 1 cm in diameter and range from white to dirty gray to brown. Dark-skinned individuals often have darker scales. Different types of scaling may be found in different areas, even in the same patient. Most scaling occurs on the extensor surfaces of the extremities, with a sharp demarcation between normal flexural folds and the surrounding affected areas.
The lower extremities generally are more affected than the upper extremities. Compared to other sites, the scales overlying the shins are thicker, darker, and arranged in a mosaic pattern. Patients often report "lizard skin" in these areas during the winter. If the trunk is involved, scaling tends to be more pronounced on the back than on the abdomen. Relative sparing of the face is seen, most likely because of increased sebaceous secretions, although the cheeks and forehead may be involved during early childhood in the hereditary form.
Dry scaling is often observed uniformly over the scalp. Sparing of the flexural folds (eg, neck, axillae, antecubital and popliteal fossae) is attributed to the relative increase in temperature and humidity in these areas. Overall symptoms of ichthyosis vulgaris generally improve in the summer months or in warm climates.
Hyperkeratosis is often present on the palms and soles, causing them to appear dirty. Skin creases in these areas are more prominent and can lead to painful fissuring, especially during dry weather. Secondary infections at fissure sites are common.
Keratosis pilaris (follicular hyperkeratosis) occurs on the side of the cheek and neck, dorsum of the upper arms, buttocks, and thighs. It consists of spiny parafollicular papules that when palpated resemble a cheese grater. Dried skin in the central portion is often white and mistaken for pus. Inflammation may or may not be present. Keratosis pilaris, which can be present without scaling, may be the only finding in family members with hereditary ichthyosis vulgaris. Keratosis pilaris may be linked to an absence of sebaceous glands, which represents an early step in keratosis pilaris pathogenesis. [39]
Pruritus can be caused by dry skin, even if inflammation is not evident. As a result, itching and scratching may lead to erythema in affected areas.
Eyelash trichomegaly, defined as increased length (≥ 12 mm), curling, pigmentation, or thickness of eyelashes, was evaluated. Eyelashes of those with atopic dermatitis and males with ichthyoses vulgaris were found to be significantly longer than those of controls. [40]
Complications
The extremities may fissure and become secondarily infected. Additional complications in acquired ichthyosis depend on the associated systemic disease.
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Hereditary ichthyosis vulgaris with thick scaling of the anterior shins.
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Hematoxylin and eosin staining of acquired ichthyosis vulgaris in an adult. Shows epidermal atrophy with thinning of the granular layer. No dermal infiltrate is evident.
