leprosy is a chronic disease caused by mycobacterium leprae affecting the peripheral nervous system , the skin , and other tissues . histoid leprosy ( hl ) is an uncommon variant of lepromatous leprosy ( ll ) , first described by wade in 1960 . it is characterized by skin colored papules and/or subcutaneous nodules and plaques on apparently normal skin with distinct histopathology and characteristic bacterial morphology . it is usually seen in patients relapsing after dapsone monotherapy and also in the presence of dapsone resistance . a 27-year - old male presented with asymptomatic papules on the trunk and extremities of 5 months duration and not associated with epistaxis , ear lobe infiltration , glove and stocking anesthesia , or hoarseness of voice . he gives a history of the hypopigmented and hypoesthetic patch on the left leg 10-years ago , diagnosed as borderline tuberculoid ( bt ) leprosy and was advised for treatment . however , he developed severe drug reaction following intake of single tablet ( most probably dapsone ) which subsequently led to exfoliation of the skin . the episode of drug reaction desisted him from taking further treatment for leprosy . on examination , there was a single , ill - defined , dry , hypopigmented , and hypoesthetic patch on the medial aspect of the right knee [ figure 1 ] . multiple dome shaped skin colored papules and nodules ( total of 129 in number ) ranging from 0.5 to 1.5 cm were distributed on the back , upper , and lower limbs . lesions were nontender , firm in consistency [ figure 2 ] , and with intact sensations . left ulnar and right lateral popliteal nerves were thickened and not tender . with these clinical features , he was offered a clinical diagnosis of bt leprosy with hl . . slit skin smears from representative nodule and both ear lobes were positive for lepra bacilli that were both solid and granular and were long and slender [ figure 3 ] . histopathological examination of biopsy from the patch ( right knee ) showed multiple epithelioid granulomas with few lymphocytes [ figure 4 ] . biopsy from the papule showed spindle cells and foam cells arranged in interlacing bundles around adnexal structures and nerve twigs in the dermis [ figure 5 ] , consistent with the diagnosis of bt leprosy with hl , respectively . he was started on antileprosy multidrug therapy consisting of rifampicin , ofloxacin , and clofazimine . irregular , ill - defined , and hypopigmented patch on the right knee multiple dome - shaped papules and nodules on the side of the trunk and right arm ziehl neelsen 's stain 100 slit skin smear from nodule showing long , slender solid , and granular lepra bacilli dermis showing epitheloid cell granulomas with few lymphocytes ( h and e , 10 ) dermis showing grenz zone and spindle cells and foam cells arranged in interlacing bundles around adnexal structures and nerve twigs ( h and e , 10 ) the term histoid is derived from the microscopic appearance of the nodule showing spindle - shaped cells resembling dermatofibroma . it is considered as a variant of ll by some researchers while others consider it as a distinct entity . the case under study is a young male aged 27 years , is in concert with reported male preponderance and the age group ( 2140 years ) reported in the literature . hl is known to be associated with dapsone resistance and also in relapse following dapsone monotherapy . however , it has also been reported with relapse in the presence of supervised monthly multidrug therapy and also in patients without any treatment . histoid lesions rarely may occur along the course of peripheral nerve trunks and peripheral nerves . morphology and distribution of skin lesions in the index case is in conformity with hl . there was no superciliary madarosis in the index case which is a notable feature in most of histoid patients and so is normal nasal mucosa . the cell - mediated immunity was found to be better in hl than in the active lepromatous patients as substantiated by increased cd36 expression by the keratinocytes , predominance of cd4 lymphocyte over cd8 lymphocytes , and increased number of activated lymphocytes and macrophages in the lesion . the humoral immunity was found to be enhanced as evidenced by increased absolute count of b lymphocytes and raised levels of immunoglobulins igg , igm , and iga . bacteriologically , there is large bacillary load in histoid lesions , which is attributed to focal loss of immunity . furthermore , the acid - fast bacilli in these cases are measurably longer than ordinary lepra bacilli , are arranged in groups or parallel bundles in spindle - shaped histiocytes , described as histoid habitus by wade . one of the significant electron microscopic features of histoid lesion is the absence of electron transparent zone or foam which is characteristically seen in lepromatous lesion . it is known that electron transparent zone ( ets ) interferes with bacterial metabolism leading to cell death . the absence of ets is said to be responsible for the preservation of bacilli within the cells in histoid lesions . the association of bt leprosy with hl in the index case is interesting as bt leprosy and hl belong to diverse immunological spectrum , former being unstable and latter being stable form . in addition , it is intriguing to note how bt leprosy moved to hl ( polar form of leprosy ) if downgrading theory is contemplated . furthermore , if bt leprosy is downgraded , then it should have moved to subpolar ll rather than to hl which is a polar form of leprosy . however , it is not known whether such association occurs due to unexplored underlying immunological mechanisms . on the contrary , the single hypoesthetic patch on right knee in the index case could not be considered as single lesion bl / ll , as the patch was dry and did not show shininess or infiltration and the histopathology also did not substantiate . nonetheless , there have been reports of single lesion bl and ll cases reported in the literature albeit not in association with histoid lesions . review of literature could reveal only two case reports of association with hl ; one with bt leprosy similar to the index case and the other with indeterminate leprosy .
coexistence of two immunologically diverse forms of leprosy in an individual is very rare . 
 herein , we report a case of association of borderline tuberculoid ( bt ) leprosy with histoid leprosy ( hl ) in a young immune competent male . he was diagnosed as a case of bt leprosy 10 years ago and now presented with multiple papules and nodules . 
 histopathological examination of biopsy taken from patch and nodule showed features of bt and hl , respectively .