Psoriasis and tuberculosis binomial distribution?

Sir,

Psoriasis affects 2-3% of world's population.[1]

Tuberculosis is the 7th cause of death all over the world, one-third of population is affected by the disease.-[2] Romania, in 2010, occupied the 6th position, after Kazakhstan, Moldavia, Georgia, Kirgizstan, and Tajikistan.[3]

In 2011, a large retrospective study was carried out on the incidence of present and past tuberculosis within 1236 psoriasis patients, not previously treated with biologics, over 2004-2011.

Of 12 patients with history of tuberculosis: Five were men (41.67%); eight cases of pulmonary tuberculosis (66.67%), two pleural effusions (16.67%), one genital tuberculosis (8.34%) and one case of keratoconjunctivitis (8.34%). Of these, One had arterial hypertension and chronic nephritis; one obesity; one erythema nodosum and one gastric carcinoma.

The second study was carried out in Pneumology Hospital in Iasi, on 3820 patients hospitalized for tuberculosis between 1 January 1, 2009 and December 31, 2012. Of these, 8 (0.21%) had psoriasis; 87.5% men (sex ratio: 7/1); 87.5% plaque psoriasis, 12.5% palmoplantar psoriasis and one erythrodermic type. Two patients had been treated with Infliximab for psoriatic arthritis and developed tuberculosis. Positive culture for Mycobacterium tuberculosis was found in four of eight; two were negative and in two patients the test was not performed (one deceased and one left the hospital before investigation).

Taking into consideration the results of both studies, we can admit that, in the absence of biological therapy, there is a very low statistical association between psoriasis and tuberculosis, despite the high prevalence of both diseases in the geographical area.