|
HealthTales.com |
|
| Index of Diseases and Conditions: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
Harlequin ichthyosis is a severe genetic disorder that mainly affects the skin. Infants with this condition are born with very hard, thick skin covering most of their bodies. The skin forms large diamond-shaped plates separated by deep cracks (fissures). These skin abnormalities affect the shape of the eyelids, nose, mouth, and ears, and restrict movement of the arms and legs. Restricted movement of the chest can lead to breathing difficulties and respiratory failure.
The skin normally forms a protective barrier between the body and its surrounding environment. The skin abnormalities associated with harlequin ichthyosis disrupt this barrier, making it more difficult for affected infants to control water loss, regulate their body temperature, and fight infections. Infants with harlequin ichthyosis often experience an excessive loss of fluids from the body (dehydration) and develop life-threatening infections during the newborn period.
Harlequin ichthyosis is very rare; its exact incidence is unknown.
Mutations in the ABCA12 gene cause harlequin ichthyosis.
The ABCA12 gene makes a protein that is essential for the normal development of skin cells. This protein appears to play a major role in the transport of lipids (fats) in the outermost layer of skin (the epidermis). Some mutations in the ABCA12 gene prevent the cell from making any ABCA12 protein. Other mutations lead to the production of an abnormally small version of the protein that cannot transport lipids properly. The loss of functional ABCA12 protein disrupts the normal development of the epidermis, preventing the skin from forming an effective barrier and resulting in the hard, thick scales characteristic of harlequin ichthyosis.
This condition is likely inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.
'''Harlequin type ichthyosis''', the most severe form of congenital ichthyosis, is characterized by a thickening of the keratin layer in fetal skin. The afflicted child is born not with skin, but massive, diamond-shaped scales. As well, the eyes, ears, mouth, and other appendages can be abnormally contracted. The scaly armor limits the child's movement, and because it is cracked where normal skin would fold, it is useless for skin's primary function -- protection. Bacterium and other contaminants easily pass into the cracks and can cause lethal infections. The term comes from both the baby's facial expression and the rhombus-shaped pattern of the scales (resembling the costume of Arlecchino), which are caused by severe hyperkeratosis. 17th century entertainers known as jesters, or harlequins, wore costumes with diamond patterns on them, as well as a particular style of face paint. The features of the harlequin fetus resemble this stylized makeup, and their faces are often pulled tight into grim parodies of a clown's smile. The disease is also known as ''harlequin ichthyosis'', ''ichthyosis congenita'', and ''keratosis diffusa fetalis''. Sufferers are known as ''harlequin fetuses'', ''harlequin babies'', or plain ''harlequins''. The underlying genetics and biochemical abnormalities that result in harlequin ichthyosis are caused by mutation in the gene ''ABCA12'', the protein encoded by this gene is is essential for the normal development of skin cells, but its role in the process is not understood. The disorder is most likely inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. The disease can be diagnosis in the womb by way of fetal skin biopsy. In the past, the disorder was invariably fatal, whether due to dehydration, infection, restricted ... [ Read More ]