The term tuberculid was first described by Darier in 1896.  Subsequently, in 1936, Pautrier established the diagnosis of papulonecrotic tuberculid as a distinct tuberculosis-associated disorder.
Although many types of tuberculids have been described, most are now understood to not be uniquely caused by tuberculosis. However, papulonecrotic tuberculids (PNTs) and lichen scrofulosorum are still widely accepted as true tuberculids.
Papulonecrotic tuberculid is a chronic, recurrent, and symmetric eruption of necrotizing skin papules arising in crops, involving primarily the buttocks and extensor surfaces of the arms and legs.  A hallmark of this condition is that lesions heal with varioliform and pitting scarring. The eruption is believed to represent a hypersensitivity reaction to tuberculosis antigens released from a distant focus of infection. Most patients react markedly to the Mantoux skin test (purified protein derivative [PPD]), may exhibit other evidence of current or past tuberculosis infection, and react quickly to antituberculous therapy. 
The pathophysiology of papulonecrotic tuberculid is controversial. Most authors believe this disease entity is triggered by an initial Arthus reaction to mycobacterial antigens. This is then followed by a hypersensitivity reaction in which antigens undergo opsonization by antibodies, followed by immune complex deposition in small cutaneous blood vessels. The ensuing complement cascade triggers a leukocytoclastic vasculitis, leading to destruction of vessel walls with ensuing tissue necrosis. Over time, this type III hypersensitivity reaction may be replaced by a type IV reaction. Other authors dispute this mechanism, citing the lack of leukocytoclastic vasculitis in some cases. Instead, they propose that the primary lesion is the result of subacute lymphohistiocytic vasculitis that leads to thrombosis and subsequent tissue necrosis.
A consensus has been reached that papulonecrotic tuberculid represents a true hypersensitivity reaction rather than the result of a local cutaneous tuberculosis infection. This is based on the observation that papulonecrotic tuberculid lesions have consistently failed to either stain positive for, or culture out, mycobacterial organisms. Although the organisms are absent, mycobacterial DNA has been detected in approximately half of the biopsy specimens subjected to polymerase chain reaction (PCR). [4, 3] These observations support the idea that lesions of papulonecrotic tuberculid are the result of released mycobacterial antigens in the setting of a concurrent but distant infection.
A decreasing incidence of papulonecrotic tuberculid began in the second half of the 1900s and the decline continues to this day. This phenomenon is attributed to aggressive tuberculosis control now found in wide practice. Currently, almost all cases come from areas outside of North America with high endemic rates of tuberculosis.  Historically, reports indicate that young women and children are especially susceptible to this disorder. 
Papulonecrotic tuberculid–like lesions have also been associated with other mycobacterial infections, including Mycobacterium bovis and Mycobacterium kansasii, and from BCG vaccination. 
Papulonecrotic tuberculid is an uncommon disorder even in populations with a high prevalence of tuberculosis, occurring in less than 5% of active tuberculosis cases. In the literature, 91 cases were reported during a 17-year period in South Africa in 1974. In addition, 12 cases from a period of longer than 30 years in England were reported in 1986. In the latter study, most patients were immigrants and had presumably acquired the infection outside of England. The incidence of tuberculosis is expected to rise as the influx of refugees from endemic areas like Africa and the Middle East continues to grow.  Freiman et al reported a case in a 25-year-old woman from the Philippines who had immigrated to Canada 8 years previously.  In a 9-year period, 4 cases were reported in Hong Kong, which was the least common of the cutaneous tuberculosis presenting during that time.  In a 5-year period, 12 cases were reported in India, a country that has the highest burden of tuberculosis in the world. [4, 10]
Females seem to be at a slightly increased risk for developing this disorder.
Children and young adults are more susceptible to this condition than other people. Papulonecrotic tuberculids represent 4% of pediatric skin tuberculosis.  In a 1974 study from South Africa, two thirds of the patients were younger than 30 years.
Without treatment, patients typically follow a waxing and waning course lasting many years, although spontaneous resolution has been reported.
Papulonecrotic tuberculids respond promptly to appropriate antituberculosis therapy. New lesions cease forming within days to weeks after therapy is initiated, and existing lesions heal rapidly, usually within weeks. Recurrences are rare after appropriate therapy.
Significant varioliform or pitted scarring is a sequela, and progression to lupus vulgaris has been observed. [11, 12] An association with Takayasu arteritis of the aortic arch has also been documented.