Mechanism of action
Interferon beta balances the expression of pro- and anti-inflammatory agents in the brain, and reduces the number of inflammatory cells that cross the blood brain barrier. Overall, therapy with interferon beta leads to a reduction of neuron inflammation. Moreover, it is also thought to increase the production of nerve growth factor and consequently improve neuronal survival. In vitro, interferon beta reduces production of Th17 cells which are a subset of T lymphocytes believed to have a role in the pathophysiology of MS.

Society and culture
Brand names
Avonex
Avonex was approved in the US in 1996, and in the European Union in 1997, and is registered in more than 80 countries worldwide. It is the leading MS therapy in the US, with around 40% of the overall market, and in the European Union, with around 30% of the overall market. It is produced by the Biogen biotechnology company, originally under competition protection in the US under the Orphan Drug Act. Avonex is sold in three formulations, a lyophilized powder requiring reconstitution, a pre-mixed liquid syringe kit, and a pen; it is administered via intramuscular injection. Rebif
Rebif is a disease-modifying drug (DMD) used to treat multiple sclerosis in cases of clinically isolated syndromes as well as relapsing forms of multiple sclerosis and is similar to the interferon beta protein produced by the human body. It is co-marketed by Merck Serono and Pfizer in the US under an exception to the Orphan Drug Act.
Rhabdomyoma is a benign mesenchymal tumor of skeletal muscle, separated into two major categories based on site: Cardiac and extracardiac. They are further separated by histology: fetal (myxoid and cellular), juvenile (intermediate), and adult types. Genital types are recognized, but are often part of either the fetal or juvenile types. The fetal type is thought to recapitulate immature skeletal muscle at about week six to ten of gestational development. Signs and symptoms
Most fetal rhabdomyomas are tumors that develop in the head and neck or in the genital region. There are a number of cases which have been seen in association with Gorlin syndrome. However, cardiac myxomas are known to be associated with tuberous sclerosis. Pathophysiology
Gross pathology
The tumor may be seen within the subcutaneous tissues (below the skin), mucosal surfaces or in soft tissue. Within the head and neck, the posterior ear region, skin of the face, and the tongue are the most commonly affected sites (about a 2:1 ratio of soft tissue to mucosa). The tumors are well defined, non-specific usually solitary masses, but when seen in the head and neck (or genital region), they may be polypoid. Tumors range in dimension from a few millimeters up to 12.5 cm, with a mean of about 3.0 cm. Although there are isolated case reports, multifocality is very rare. Microscopic pathology
Fetal rhabdomyoma are separated into two histologic types: Myxoid and cellular. However, irrespective of histologic type, these tumors almost never show necrosis or increased mitoses. However, a cambium layer, abnormal mitoses and nuclear pleomorphism is not seen.