All are true about rheumatic fever, except –
(A) Common in poor socioeconomic group (B) Develops after streptococcal pharyngitis (C) Communicable disease (D) Seen in 5–15 years of children
(C) Rheumatic fever

Rheumatic fever is an acute immunologically mediated multisystem inflammatory disease that occurs few weeks after an episode of group A streptococcal pharyngitis.
The disease is immune mediated, not a communicable disease.
	Epidemiology ofAcute Rheumatic fever.
The epidemiology of acute Rheumatic fever is identical to that of group A streptococcal upper respiratory tract infection.
As is the case of streptococcal sore throat, acute rheumatic fever most often occurs in children, the peak age related incidence is between 5-15 years.
Epidemiological risk factor for rheumatic fever, include lower standards of living especially crowding, the disease has been more common among socially and economically disadvantaged populations.

Pathogenesis of Rheumatic fever

It is strongly suspected that acute Rheumatic fever is a hypersensitivity reaction induced by group A streptococci but the exact pathogenesis remains uncertain despite many years of investigation.
Although the precise factor or factors that confer this property are unknown, highly rheumatogenic strains, share certain biological characteristic.
It is believed that antibodies directed against the M proteins of certain strains cross reacts with glycoprotein antigens in the heart, joints and other tissues. These strains are (1, 3, 5, 6, 18).
The M proteins molecules has a particular surface exposed antigenic domain against which Rheumatic fever patients mount a strong antibody response. These antibodies against the M proteins cross reacts with glycoproteins antigens in the heart, joints and other tissues because these glycoproteins share similar features with M antigenic domain.