Tuesday, July 3, 2012

Laboratory Studies

Genetic testing for mutations in the ABCA12 gene is available. Complete sequence analysis of the coding region of this gene is performed to identify specific mutations. Peripheral blood cells or cells from buccal smear from affected individuals are required. Carrier testing is available for a relative after the proband’s mutation is identified. Prenatal diagnosis is available for fetuses with suspected harlequin ichthyosis, which may or may not have a family history of the disorder.

The following laboratory investigations may be helpful for newborn to identify complications of harlequin ichthyosis.
ü  Check the WBC count and blood cultures for signs of infection.
ü  Closely monitor serum electrolyte levels, which may be abnormal secondary to dehydration.
ü  Check BUN and creatinine levels for signs of renal failure.
ü  Monitor hemoglobin levels because anemia is reported.
Prenatal 3-Dimensional (3D) ultrasonography may show features suggestive of harlequin ichthyosis.
Chest Radiography may be indicated if respiratory distress is present postnatally.
Renal Ultrasonography may be indicated if renal failure or poor urine output is evident or if findings from the physical examination are abnormal. Renal dysplasia is indicative to harlequin ichthyosis.
Skin Biopsy at any cutaneous site (including the palms and the soles, excluding mucous membranes) may be done to acess the histopathologic characteristics and ultrastructural features.

Histologic Findings

The stratum corneum is thick and compact. Hyperkeratosis may be more marked around hair follicles compared with the interfollicular epidermis. Parakeratosis and orthokeratosis may be present, particularly on the fingers and the toes. Cells within the stratum corneum are abnormally keratinized. Granular, spinous basal cell layers appear unremarkable. Inflammatory cells may infiltrate the papillary dermis.

Electron Microscopy reveals absent or abnormal lamellar granules within the granular layer keratinocytes. Lamellae are absent in the intercellular spaces between the granular cell layer and the cornified cell layer. Densely packed lipid droplets and vacuoles are seen within the cytoplasm of the aberrantly cornified cells of the stratum corneum. These lipid inclusions involve the entire skin surface but are more evident on the palms and the soles. Keratohyalin granules may be absent, normal, or abnormally small and globular. Keratin intermediate filaments within granular cells may have reduced density.
ü  Amniotic fluid can be tested for over production of ‘Keratin’ in 17th weeks of pregnancy to disgnosize this disease in early stage.
ü  Foetal skin biopsy can be done at 20th week of pregnancy for early detection of harlequin ichthyosis. 

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