T - cell immunodeficiency, congenital alopecia and nail dystrophy (T-cell immunodeficiency, congenital alopecia and nail dystrophy) - Gen FOXN1.
T cell immunodeficiency, congenital alopecia and nail dystrophy is a type of severe combined immunodeficiency (SCID). People with this form of SCID have a deficiency or absence of functional T cells, which normally recognize and attack foreign invaders to prevent infection. No functional T cells, affected individuals develop persistent recurrent infections since the beginning of life. These infections cause slow growth and can be fatal. Without effective treatment, those most affected live only in infancy or early childhood.
This disease also affects the growth of hair and nails. Congenital alopecia is evident from birth. Because of this, the people affected have no hair on the scalp, eyebrows or eyelashes. For its part, the nail dystrophy manifests with fluted or abnormally curved nails. Furthermore, they described abnormalities of central nervous system in at least two cases of T - cell immunodeficiency, congenital alopecia and nail dystrophy. However, it is still unclear whether abnormalities of the central nervous system are a common feature of this disease.
This process is due to mutations in the gene FOXN1, located on the long arm of chromosome 17 (17q11.2). This gene encodes a protein transcription factor which is important for the development of skin, hair, nails and immune system. Studies suggest that this protein helps guide the formation of hair follicles and growth of fingernails and toenails. The FOXN1 protein also plays a critical role in the formation of thymus where T immune cells mature and become functional. T cells recognize and attack invaders such as viruses and bacteria, to help prevent infection. In addition, it is believed that FOXN1 protein is also involved in the development of the central nervous system, although its role is unclear.
It described at least one mutation in the gene for FOXN1 T - cell immunodeficiency, congenital alopecia and nail dystrophy. The Arg255Ter or R255X mutation replaces the amino acid arginine with a stop signal in encoding proteins, so no protein is not synthesized. Deficiency or absence of proteins FOXN1 prevents the formation of the thymus. When this gland is not present, the immune system can not produce mature functional T cells to fight infections. As a result, affected individuals develop recurrent severe infections. Furthermore, loss of FOXN1 protein inhibits the formation of hair follicles, leading to alopecia. Similarly, the absence or deficiency of this protein causes nail dystrophy. However, it is unclear how FOXN1 protein deficiency may contribute to these anomalies.
This disease is inherited in an autosomal recessive pattern, which means that both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with T - cell immunodeficiency, congenital alopecia and nail dystrophy, by complete PCR amplification of exons FOXN1 gene, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).