When diagnosing ichthyosis, a skin biopsy is usually not necessary as the condition is fairly obvious. There is as previously mentioned, a continuum between dry skin and ichthyosis. Ichthyosis vulgaris is distinguished from less common types of ichthyosis on bases of inheritance, type and distribution of scaling. Acquired ichthyosis is different from ichthyosis vulgaris as it has a sudden onset in adulthood, and is often associated with an underlying systemic disease such as hodgkenson's disease, leprosy, lymphoma, renal failure and hypothyroidism. Palms and soles are normal, there is no keratosis pilaris, and associated findings include corneal opacities.
Lamellar ichthyosis is autosomal recessive which appears at birth.
Scales are large, thick, and over most of the body, including the flexures. This form of ichthyosis is commonly associated with a 'collodion baby' which is an infant born completely covered in a cellophane like membrane. This membrane subsequently peels off, sometimes desquamating in large sheets. Currently there is no known treatment for ichthyosis but continuous, lifelong therapy is essential. Therapy aims at increasing the water content or preventing moisture evaporation of the stratum corneum.