Lichen scrofulosorum: A diagnosis overlooked.

Lichen scrofulosorum, also known as "tuberculosis cutis lichenoides," is a rare tuberculid that presents as a lichenoid eruption of minute papules in children and adolescents with tuberculosis. The lesions are usually asymptomatic, closely grouped, skin-colored to reddish-brown papules, often perifollicular, and are mainly found on the abdomen, chest, back, and proximal parts of the limbs. The eruption is usually associated with a strongly positive tuberculin reaction. Diagnosis of these lesions can be difficult, as they resemble many other dermatological conditions that are often primarily considered. We report a case of lichen scrofulosorum in an adult male without any focus of tuberculosis. He responded promptly to antitubercular therapy with complete clearance of lesions in one month.

INTRODUCTION

Lichen scrofulosorum (LS) also known as tuberculosis (TB) cutis lichenoides, is a rare tuberculid that presents as a lichenoid eruption of minute papules in children and adolescents with TB. The lesions are usually asymptomatic, closely grouped, skin-colored to reddish-brown papules, often perifollicular, and are mainly found on the abdomen, chest, back, and proximal parts of the limbs. The eruption is usually associated with a strongly positive tuberculin reaction.[1]

CASE REPORT

We report a case of 23-year-old male who presented to us with multiple small erythematous to skin-colored, mostly perifollicular papules over forearms [Figure 1], dorsum of hands [Figure 2], shoulders, forehead [Figure 3] and scapular region since 15 days. The lesions were mildly itchy. There was no history of fever, cough, anorexia, weight loss, or any other systemic symptoms. He had no past or family history of TB. No lymphadenopathy or organomegaly was present. Systemic examination of the respiratory, cardiovascular, abdominal and central nervous systems did not reveal any abnormalities. Examination of hair, nails and mucosal surfaces was normal.

Figure 1

Papular lesions over forearm

Figure 2

Papular lesions over dorsum of hands

Figure 3

Papular lesions over forehead

Initially, the patient was treated as a case of miliaria and given calamine lotion; however, when there was no improvement after 1 week, other differentials like LS, keratosis pilaris, lichen spinulosis, lichen nitidus, and secondary syphilis were considered. X ray chest was done which was normal; USG abdomen was also insignificant; and Mantoux test was strongly positive [Figure 4] with 18 mm induration, which pointed toward an active tubercular process. Serum venereal disease research laboratory (VDRL) test and human immunodeficiency virus- enzyme linked immunosorbent serologic assay (HIV-ELISA) were nonreactive. A biopsy was done which showed focal lichenoid tuberculoid granulomatous inflammation. Granuloma in the papillary dermis was impinging onto the epidermis, which showed mild spongiotic psoriasiform changes. [Figure 5]. Cutaneous nerves were spared. This confirmed the diagnosis of LS. No tubercular foci could be detected on screening. Patient was started on CAT I antitubercular therapy (ATT) with four drugs (rifampicin, isoniazid, ethambutol and pyrazinamide) for the first two months, followed by rifampicin and isoniazid for six months. His skin lesions cleared completely by one month [Figures 6 and 7].

Figure 4

Positive Mantoux test

Figure 5

Focal lichenoid tuberculoid granulomatous inflammation in the lesional skin biopsy (H and E, ×40)

Figure 6

Post-treatment photo of hands

Figure 7

Post-treatment photo of forehead

DISCUSSION

Tuberculids are a group of skin conditions associated with an underlying or silent focus of TB. Conditions in this group include: papulonecrotic tuberculid, LS, erythema induratum of Bazin, and erythema nodosum.

LS is a rare tuberculid, initially described by Hebra in 1860.[2] It is clinically characterized by tiny, skin-colored, perifollicular papules arranged in groups; normally, they have a smooth surface, but occasionally spiny projections with fine scales may be seen. Histology shows non-caseating, epithelioid cell granulomas in upper dermis and around dermal appendages. Tubercle bacilli are almost never seen in the histology specimen, neither can they be cultured. However, rarely antigen of mycobacterial TB has been demonstrated in papulonecrotic tuberculid, another type of more frequently seen tuberculid.[3]

In a study of 39 cases of LS by Singhal et al., 72% cases had an underlying focus of TB and 28% cases had no identifiable focus.[4] In this case, there was no evidence of tubercular infection presently or in the past.

Diagnosis of these lesions can be difficult, as they resemble many other dermatological conditions that are often primarily considered. The differential diagnosis may include lichen spinulosus, lichen nitidus, keratosis pilaris, pityriasis rubra pilaris, and lichenoid sarcoidosis.

CONCLUSION

Correct diagnosis of LS is frequently delayed because of its rarity and clinical similarity to many other more common skin conditions. However, it should be considered in patients presenting with persistent papular lesions not responding to other therapies. It is imperative that dermatologists have a high index of suspicion in order to quickly diagnose and treat this condition. A proper history and physical examination as well as diligent laboratory and diagnostic testing can determine the presence of occult tubercular focus; substantial morbidity can be prevented by very effective conventional ATT.