Papulonecrotic tuberculid in a patient with pulmonary tuberculosis.

A 55-year-old male presented with recurrent crops of crusted papular lesions and boils over buttocks for 1month along with a short history of productive cough. The diagnosis of papulonecrotictuberculid (PNT) with pulmonary tuberculosis was made based on history, clinical features, laboratory investigations, and response to antitubercular treatment.

INTRODUCTION

Papulonecrotic tuberculid (PNT) is an asymptomatic, chronic disorder, occurring in crops associated with an underlying or silent focus of tuberculosis. The lesions are symmetrically distributed over the extensors of extremities, dorsum of hands and feet, face, and ear.[1] Our patient presented with recurrent crops of crusted papular lesions on extensor surface of upper limbs and back for 1month and boils over buttocks for 20 days. He gave history of productive cough for 15 days. On examination and investigations, a diagnosis of PNT with pulmonary tuberculosis was made.

CASE REPORT

A 55-year-old male presented with recurrent crops of crusted papular lesions on extensor surface of upper limbs and back for 1month and boils over buttocks for 20 days. He also gave history of productive cough for 15 days and occasionally he coughed out blood-tinged sputum. On examination, multiple papules with crusting and central necrosis were seen on bilateral extensor surface of upper limbs with clustering of lesions around elbows and the back [Figures 1 and 2]. Few nodules with central necrosis were seen on buttocks and scalp. One ulcer of size 4×4cm with necrotic base and surrounding erythema were seen on left buttock [Figure 3].

Figure 1

Clinical photograph showing crusted papules on the back

Figure 2

Clinical photograph showing crusted papules around the elbows

Figure 3

Clinical photograph showing ulcer on buttock and nodules with crusting

Investigations revealed raised ESR 55 mm/h (Westergren), with evidence of tuberculosis on chest X-ray in bilateral lung fields. His Mantoux was strongly positive with induration of 20 mm. Sputum for AFB was positive. Biopsy from the lesion on the right elbow revealed a single focus of leucocytoclastic vasculitis affecting a small- to medium-sized vessel in mid-dermis. Surrounding this focus was dense neutrophilic inflammation. Upper dermis showed large subepidermal pustule with marked edema. There was no granuloma. These features were consistent with PNT [Figures 4 and 5]. Rest of the investigations like complete blood count, liver function tests and renal function tests were within normal limits.

Figure 4

Histopathology showing subepidermal pustule, neutrophilic inflammation with vasculitis (H and E, ×100)

Figure 5

Histopathology showing subepidermal pustule, neutrophilic inflammation with vasculitis (H and E, ×400)

Patient was started on multidrug therapy (MDT) consisting of rifampicin 600 mg, isoniazid 300 mg, pyrazinamide 1500 mg, and ethambutol 800 mg. On starting therapy, many lesions on back disappeared within 2weeks. His general condition has improved and at 4weeks of therapy, he has no cough. He is still on MDT and his skin lesions are healing with scarring.

DISCUSSION

In 1896, Darier introduced the concept of “tuberculids,” the clinical manifestations of which include PNTs, lichen scrofulosorum, and erythema induratum of Bazin. The entity is still being questioned today because the clinical and histological appearances are not very specific.[2] It is thought to represent an Arthus phenomena in a person with a moderate or high degree of immunity to the tubercle bacilli. The underlying focus may not be evident at that time.[3] The pathophysiology of this condition is controversial. The most commonly held view is that PNT represents a hypersensitivity reaction to TB antigens released from a distant focus of infection.[4] Evidence of TB elsewhere is reported in up to 40% of patients.[5] Prompt response to antituberculosis treatment is its hallmark.[6]

The basic diagnostic criteria for PNTs are: A strongly positive Mantoux test, typical clinical features, a tuberculoid histology with endarteritis and thrombosis of the dermal vessels, and response to antituberculous therapy (ATT).[7] The histological findings may be sometimes inconclusive, showing a nonspecific or tuberculoid picture.[8]

PNT is a rare manifestation even in areas endemic for tuberculosis. There are few case reports of PNT associated with an underlying pulmonary tuberculosis as in our case.[9]