Background:Papulonecrotic tuberculid (PNT) is said to be a hypersensitivity reaction to M. tuberculosis. Some reports indicate that organisms are demonstrable by polymerase chain reaction (PCR).Methods:We describe 12 patients with PNT over 6 years. We reviewed the histopathologic features, clinical data and follow-up. PCR for M. tuberculosis DNA was done in all cases.Results:There were 7 men and 5 women. The ages ranged from 3–58 years. Upper limbs were commonly involved (8 cases). All patients had multiple papulonodular lesions, 5 showed ulceration and scarring. Mantoux test was strongly positive in all. Seven patients had systemic tuberculosis.On microscopy, necrosis was seen in 11 cases, varying from minimal to extensive. Epithelioid granulomas were common, except for 1 case with palisading and interstitial patterns. The infiltrate showed mostly lymphocytes, while 3 cases showed eosinophils. Vasculitis was seen in 8 cases. Two cases had dermal mucin, one also with interface dermatitis. This patient had concurrent LE. Mycobacterial DNA was detectable by PCR in 3 cases. Seven patients showed improvement/resolution of lesions on treatment.Conclusions:PNT is a rare disease. A positive PCR reiterates the question whether these are “tuberculids”. PNT may be better classified as true cutaneous tuberculosis and patients screened for systemic disease.

Histopathology supplemented by immunohistochemistry is reliable in making a diagnosis of HMF. It is important to be aware of this uncommon, yet significant disease.

Background:Histopathologic diagnosis of borderline tuberculoid leprosy (BTL) is fraught with hurdles. It overlaps with other granulomas and documenting nerve involvement is the key to correct diagnosis. This is difficult on H and E sections alone. S-100 immunostaining may help in this regard.Objectives:To study the patterns of nerve involvement in BTL and other cutaneous granulomas using S-100 immunostain and compare its sensitivity with that of H and E staining, in both adequate and inadequate biopsies.Materials and Methods:A total of 20 cases of BTL were reviewed. And, 19 biopsies from other cutaneous granulomas were taken as controls. S-100 immunostaining was done on paraffin sections. The pattern of nerve involvement was graded as intact, infiltrated and/or fragmented, intact with perineural inflammation.Results:Of the 20 cases of BTL, S-100 demonstrated infiltrated and/or fragmented nerves in 15 and absent nerves in 5 cases. H and E stain identified neuritis in eight cases. The sensitivity of S-100 and H and E is 0.78 and 0.41. In the 19 controls, S-100 identified normal nerves in 16 with 7 showing perineural inflammation only and their absence in 2 cases. H and E identified normal nerves in nine cases. The sensitivity of S-100 and H and E is 0.83 and 0.41. In biopsies where subcutis was absent, the sensitivity of S-100 in identifying nerve involvement is 0.66 compared with H and E 0.33.Conclusion:S-100 staining is an efficient ancillary aid in distinguishing BTL from other granulomas and is superior to H and E in identifying nerve involvement, even where subcutis is absent. Infiltration and/or fragmentation of nerves by S-100 is the only reliable marker of BTL.

No abstract

No abstract