T-cell acute lymphoblastic leukemia may refer to:

T-lymphoblastic leukemia/lymphoma, a form of lymphoid leukemia and lymphoma
Adult T-cell leukemia/lymphoma, a rare cancer of the immune systems own T-cells
Björnstad syndrome is an autosomal recessive congenital condition involving pili torti, sensorineural deafness, and hair abnormalities. It was first characterized in 1965, in Oslo, by prof. Roar Theodor Bjørnstad after he observed an association between pili torti and hearing loss. The condition is extremely rare, with less than 50 cases documented in medical literature worldwide.Björnstad syndrome is caused by mutations of the BCS1L gene. The protein product of this gene is BCS1L, which plays an important role in oxidative phosphorylation. Mutated BCS1L increases production of reactive oxygen species, which may be the molecular cause of pili torti and hearing loss, both of which are associated with Björnstad syndrome. Pili torti is recognized in early childhood and is characterized by twisted hair shafts and brittle hair. The hearing loss usually becomes evident very early in life as well, often in the first year. Signs and symptoms
The two major symptoms of Björnstad syndrome are pili torti and sensorineural hearing impairment. These two symptoms typically appear before the age of 2 and are present in 80-99% of individuals with Björnstad syndrome. Approximately 5-29% of individuals also experience intellectual disabilities and hypogonadism. Cases showing lack of hair pigmentation and anhidrosis have also been documented.Pili torti is a hair abnormality characterized by twisted hair shafts. In Björnstad syndrome patients, the hair usually appears dry, fragile, coarse, and is easily broken. In some patients, hair abnormalities only affect hair on the head, although cases affecting eyebrows, eyelashes, and hair on other parts of the body have been documented.