Major criteria
Joint manifestations are the unique clinical signs that have different implications for different population-risk categories : Only polyarthritis (a temporary migrating inflammation of the large joints, usually starting in the legs and migrating upwards) is considered as a major criterion in low-risk populations, whereas monoarthritis, polyarthritis and polyarthralgia (joint pain without swelling) are all included as major criteria in high-risk populations. Carditis: Carditis can involve the pericardium (pericarditis which resolves without sequelae), some regions of the myocardium (which might not provoke systolic dysfunction), and more consistently the endocardium in the form of valvulitis. Carditis is diagnosed clinically (palpitations, shortness of breath, heart failure, or a new heart murmur) or by echocardiography/Doppler studies revealing mitral or aortic valvulitis. Both of clinical and subclinical carditis are now considered a major criterion. Subcutaneous nodules: Painless, firm collections of collagen fibers over bones or tendons. They commonly appear on the back of the wrist, the outside elbow, and the front of the knees. Erythema marginatum: A long-lasting reddish rash that begins on the trunk or arms as macules, which spread outward and clear in the middle to form rings, which continue to spread and coalesce with other rings, ultimately taking on a snake-like appearance. This rash typically spares the face and is made worse with heat. Sydenhams chorea (St. Vitus dance): A characteristic series of involuntary rapid movements of the face and arms. This can occur very late in the disease for at least three months from onset of infection.
Schwannomatosis is an extremely rare genetic disorder closely related to the more-common disorder neurofibromatosis (NF). Originally described in Japanese patients, it consists of multiple cutaneous schwannomas, central nervous system tumors, and other neurological complications, excluding hallmark signs of NF. The exact frequency of schwannomatosis cases is unknown, although some populations have noted frequencies as few as 1 case per 1.7 million people.Schwannomas are mostly benign tumors that commonly occur in individuals with NF2 and schwannomatosis (sometimes called neurofibromatosis type III). Schwann cells are glial cells that myelinate the axons of nerve cells. Myelin is a lipid covering that speeds the conduction of action potentials. When Schwann cells proliferate out of control in an encapsulation it is called a schwannoma. Although schwannomas are benign they become detrimental when the growing tumor compresses the nerve. Schwannomas on sensory nerve axons cause chronic severe pain. Treatment options for schwannomas are to surgically remove them, have radiation, cyberknife or Intracapsular Enucleation. Previous designations for schwannomas include neurinoma and neurilemmoma. Cause
The candidate schwannomatosis gene, named SMARCB1, is a tumor suppressor gene that regulates cell cycle, growth and differentiation. An inactivating  germline mutation in exon 1 of the tumor suppressor gene SMARCB1 has been reported in patients with schwannomatosis. It is located on chromosome 22 a short distance from the NF2 gene.