Tests
1st tests to order
skin biopsy
Test
If clinical suspicion is high for epidermolytic ichthyosis, this is an initial test.
Unfortunately, the histologic features of the other primary ichthyoses are less specific. Consequently, if any of the other ichthyoses are suspected, skin biopsy would not likely be performed on the first visit as the biopsy findings are not specific enough for diagnosis and other studies (e.g., biochemical or genetic studies) may be necessary.
Result
hyperkeratosis, hypergranulosis, and epidermolysis in bullous ichthyosiform erythroderma; findings in other primary ichthyoses are nonspecific
serum cholesterol sulfate
Test
Elevated serum cholesterol sulfate is diagnostic for X-linked ichthyosis.
Test is not widely available.
Result
elevated (2000 to 9000 micrograms/dL) in X-linked ichthyosis
lipoprotein electrophoresis
Test
Can be used as an alternative test for X-linked ichthyosis if serum cholesterol sulfate test is not available, although it is not as sensitive.
Result
increased mobility of beta-lipoproteins in X-linked ichthyosis
steroid sulfatase activity
Test
Diminished steroid sulfatase activity is diagnostic for X-linked ichthyosis.
Test is not widely available.
Result
decreased activity in X-linked ichthyosis
Tests to consider
serum phytanic acid
Test
Refsum disease is a very rare form of ichthyosis with systemic findings including cerebellar ataxia, peripheral neuropathy, cranial nerve dysfunction, and ECG abnormalities.[17]
Test is not widely available and would not be commonly ordered in most patients who present with ichthyosis.
Result
elevated in Refsum disease
genetic testing
Test
Limited by availability and the presence of genetic heterogeneity in certain forms of ichthyosis.[5] If clinical suspicion is high, these tests may be considered first-line testing.
Result
shows genetic defects characteristic of various ichthyoses, including some very rare subtypes
CT scan
Test
Acquired ichthyosis related to an underlying disease may necessitate a variety of investigations to pinpoint the exact diagnosis.
Result
may reveal lymphoma in cases of acquired ichthyosis
serum glucose
Test
Acquired ichthyosis related to an underlying disease may necessitate a variety of investigations to pinpoint the exact diagnosis.
Result
may be elevated in cases of diabetes mellitus-associated acquired ichthyosis
antinuclear antibody
Test
Acquired ichthyosis related to an underlying disease may necessitate a variety of investigations to pinpoint the exact diagnosis.
Result
evidence of autoimmune disease in cases of systemic lupus erythematosus associated acquired ichthyosis
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