Indian Journal of Dermatology
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Table of Contents 
Year : 2021  |  Volume : 66  |  Issue : 4  |  Page : 425-427
Papulonecrotic Tuberculid (PNT) Manifesting as Koebner Phenomenon; Hitherto Unreported Observation

1 Department of Dermatology and STD, University College of Medical Sciences and GTB Hospital (University of Delhi), Delhi, India
2 Department of Pathology, University College of Medical Sciences and GTB Hospital (University of Delhi), Delhi, India

Date of Web Publication17-Sep-2021

Correspondence Address:
Archana Singal
Department of Dermatology and STD, University College of Medical Sciences and GTB Hospital (University of Delhi), Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijd.IJD_302_19

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How to cite this article:
Kharghoria G, Singal A, Pandhi D, Tanveer N. Papulonecrotic Tuberculid (PNT) Manifesting as Koebner Phenomenon; Hitherto Unreported Observation. Indian J Dermatol 2021;66:425-7

How to cite this URL:
Kharghoria G, Singal A, Pandhi D, Tanveer N. Papulonecrotic Tuberculid (PNT) Manifesting as Koebner Phenomenon; Hitherto Unreported Observation. Indian J Dermatol [serial online] 2021 [cited 2023 Feb 1];66:425-7. Available from:


A 32-year-old woman from Bihar presented with mildly pruritic, dusky red to brown-colored pea-sized necrotizing papules along with atrophic varioliform scars present symmetrically with predominant involvement of the extremities and trunk, sparing head, neck, palms, and soles of 6 months duration. The arrangement was characteristically linear at many places on the upper back and thigh suggestive of the Koebner phenomenon [Figure 1]. Multiple discrete, non-tender right axillary and bilateral inguinal lymph nodes were palpable with normal overlying skin. She had a history of easy fatigability, low-grade fever, and decreased appetite with a feeling of abdominal fullness. There was no personal or family history of tuberculosis. A clinical differential diagnosis of acquired reactive perforating collagenosis and papulonecrotic tuberculid were considered. Investigations showed anemia (9.2 gm% and microcytic hypochromic picture on peripheral smear) and an elevated erythrocyte sedimentation rate (ESR) (60 mm in the 1st hour). The rest of the blood biochemistry was normal. X-ray chest postero-anterior (PA) view revealed no abnormality. Mantoux test with 1 TU of purified protein derivative (PPD) was strongly positive (28 mm induration). Ultrasonography of the abdomen revealed multiple mesenteric and para-aortic lymph nodes varying in size with evidence of necrosis and calcification in a few suggestive of abdominal tuberculosis. Histopathology from a necrotic papule revealed a subepidermal pustule with dense neutrophilic infiltrate and leukocytoclastic vasculitis in the upper dermis; however, no granuloma was seen [Figure 2] and [Figure 3]. Lesional polymerase chain reaction (PCR) was negative for Mycobacterium tuberculosis (M.tb). Fine-needle aspiration cytology from inguinal lymph node showed granulomatous tissue reaction consistent with tuberculosis with acid-fast bacilli (AFB) staining negativity. Based on the clinical, cytological, and histopathological examination, a diagnosis of papulonecrotic tuberculid (PNT) with Koebner phenomenon was made and the patient was started on standard first-line anti-tubercular therapy (ATT) for 6 months. The patient continued her treatment from Bihar and telephonically confirmed resolution of all the lesions within 2 months of starting ATT as she did not come back for follow-up.
Figure 1: Papules and plaques with central necrosis of PNT present over the back, buttocks, and thighs showing linear arrangement suggestive of the Koebner phenomenon. Note induced Koebner's phenomenon (Black arrows)

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Figure 2: Photomicrograph showing the histopathology of the case: Large subepidermal pustule with marked edema and dense neutrophilic infiltrate (Hematoxylin and Eosin 100X)

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Figure 3: Photomicrograph showing dense inflammation with leukocytoclastic vasculitis in the upper dermis (Hematoxylin and Eosin, 400X). No granuloma was seen

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PNT is a rare cutaneous hypersensitivity reaction to M.tb, generally from an extracutaneous focus of infection;[1] the lymph nodes and lung being the most common underlying sites. It presents most frequently in children and young adults with multiple cutaneous 2–8 mm necrotizing papules appearing in crops, primarily involving extensors of the extremities and healing with varioliform scarring.[2] Histopathology of PNT shows vascular involvement in the form of leukocytoclastic or lymphocytic vasculitis with fibrinoid necrosis and thrombotic occlusion of individual vessels with subsequent formation of an area of wedge-shaped necrosis. Granuloma formation may be absent and AFB stain is negative.

The diagnosis requires a high index of suspicion as it simulates other dermatological conditions like acquired perforating collagenosis, perforating granuloma annulare, and pityriasis lichenoides et varioliformis acuta. Koebner (isomorphic) phenomenon is a well-known phenomenon classically described in association with lichen planus, psoriasis, and vitiligo. It has also been recently reported in classic tuberculid, lichen scrofulosorum.[3] Its exact pathogenesis is not known; however, a number of pathogenetic factors are implicated: immunologic, vascular, dermal, enzymatic, inhibitory, neural, growth, genetic, and hormonal.[3]

In our case, the strongly positive Mantoux test, characteristic histopathology from the skin as well as associated underlying tubercular lymphadenitis and abdominal Koch's confirmed the diagnosis of PNT. The lesional PCR for mycobacterial deoxyribonucleic acid (DNA) was found negative in our case. Although PCR positivity has been demonstrated in up to 80% of the patients,[4] a recent Indian study has found a positive result only in 25% of the cases.[5] The characteristic linear arrangement of the lesions suggests the existence of Koebner phenomena in PNT. We present this case to bring forward this new observation in PNT for the first time and to reiterate the importance of high clinical suspicion to arrive at the correct diagnosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for his images and other clinical information to be reported in the journal. The patient understood that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Singal A, Bhattacharya SN. Lichen scrofulosorum: A prospective study of 39 patients. Int J Dermatol. 2005;44:489-93.  Back to cited text no. 1
Wong S, Rizvi H, Cerio R, O'Toole EA. An unusual case of vulval papulonecrotic tuberculid. Clin Exp Dermatol 2011;36:277-80.  Back to cited text no. 2
Pandhi D, Singal A, Wadhwa N. Lichen scrofulosorum: Yet another disease manifesting the Koebner phenomenon?. Int J Dermatol 2016;55:809-10.  Back to cited text no. 3
Jordaan HF, Van Niekerk DJ, Louw M. Papulonecrotic tuberculid. A clinical, histopathological and immunohistochemical study of 15 patients. Am J Dermatopathol 1994;16:474-85.  Back to cited text no. 4
Tirumalae R, Inchara YK, Antony M, George G, Kenneth J. Papulonecrotic tuberculid—clinicopathologic and molecular features of 12 Indian patients. Dermatol Pract Concept 2014;4:17-22.  Back to cited text no. 5


  [Figure 1], [Figure 2], [Figure 3]


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