Lepromin Test Research Articles

Clinical profile of patients with pure neuritic leprosy: 20 years’ experience at a tertiary referral centre from North India

Introduction Pure neuritic leprosy (PNL) is characterized by enlargement of peripheral nerves, sensory loss without any cutaneous lesions, skin slit smear negativity and a variable lepromin test and histopathology. Methods This was a retrospective analysis of the clinical records of all the leprosy patients enrolled in the Leprosy Clinic, during the years 1999–2019. The patient records fulfilling the diagnostic criteria of PNL were considered for analysis. Results A total of 1225 patients registered leprosy cases, out of which 41 (3.3%) patients were diagnosed with PNL. Mean age was 31 years and 80% patients were male. Multiple nerves were affected in 25 (61%) patients and one nerve was found to be affected in only 16 (39%) patients. Grade 2 deformities were seen in 26 (63%) patients. All patients were treated with multi-drug therapy - 25 patients received the multibacillary regimen and 16 received the paucibacillary regimen; 27 (66%) patients completed the treatment as prescribed. Conclusion Leprosy is the most common treatable cause of peripheral neuropathy. Therefore, early detection of leprosy neuropathy is important for preventing deformities and disabilities. It may be advisable to treat all PNL cases with the multibacillary multidrug therapy in view of higher rate of deformities.

DESTRUCTIVE LESION OF THE ANTERIOR MANDIBLE: A UNIQUE PRESENTATION OF LEPROSY

Leprosy is a chronic disease caused by infection with Mycobacterium leprae. The disease has an incubation period spanning 1-20 years with an average duration of 5 years. According to the CDC, 150-200 people in the US and 250,000 people worldwide become infected with leprosy yearly. From 2006-2015, Southeast Asia reported the highest number of new cases per year. Here we report an unusual case of intraosseous leprosy of the mandible from a 31-year-old Indian-American female. The woman presented to her oral surgeon with a destructive lesion of the anterior mandible and had associated loose teeth. She reported both prior and recent trips to India. Clinical impression at the time of surgery was a central giant cell granuloma or ameloblastoma. Histopathologic examination revealed granulomatous inflammation composed of histiocytes admixed with lymphocytes, plasma cells, and neutrophils. Discrete granulomas composed of epithelioid histiocytes and multinucleated giant cells were noted. Due to the histologic findings, GMS, PAS, and AFB Ziehl-Nielsen stains were ordered and all were reported as negative. AFB Fite stains demonstrated rare positivity. The case was diagnosed as chronic granulomatous inflammatory reaction with focal Fite stain positivity, suggestive of leprosy. While the histology is suggestive of tuberculoid leprosy, correlation with systemic evaluation and lepromin skin test were recommended. The utility of the lepromin test is to better classify the type of leprosy the patient has with positive results indicating either tuberculoid or borderline leprosy and a negative reaction supporting a diagnosis of lepromatous leprosy. Few extragnathic bony cases and intraoral cases have been reported in the English literature since 1965. This case report illustrates both an unusual and interesting case of gnathic leprosy, as well as the need to recognize that with the ease of travel, lesions that are historically seen in countries other than the United states, can be seen here.

Increased Langerhans cell accumulation after mycobacterial stimuli

Aims:To evaluate the role of Langerhans cells (LCs) in the local activation of leprosy lesions. LCs, acting as tolerance inducers and immune stimuli, are dendritic cells recently implicated in cutaneous homeostasis. The role of LCs in the defence against mycobacterial infection remains poorly understood.Methods and results:The number and distribution of CD1a+ skin cells and HLA-DR and intercellular adhesion molecule (ICAM)-1 expression were analysed in leprosy skin lesions and in delayed-type hypersensitivity (DTH) tests. The results showed a high number of LCs in tuberculin and lepromin tests, in tuberculoid lesions and in the epidermis and dermis during type I and II reactions. In multibacillary lesions, however, the number of LCs was consistently low in comparison with other groups. Increased numbers of LCs were accompanied by marked HLA-DR and ICAM-1 expression, suggesting a strong relationship between these immunological events.Conclusions:CD1a+ cells are implicated in the local immunological events taking place after mycobacterial stimuli and may account for the local activation of all types of reactional episodes in leprosy.

Emergence of an effective adaptive cell mediated immune response toMycobacterium lepraeis not impaired in reactive oxygen intermediate-deficient mice

Cytokine-activated macrophages (MPhi) employ reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) to combat pathogens. The requirement for ROI for an effective host response to experimental leprosy using mice which have a disruption in the 91-kD subunit of the NAPDH oxidase cytochrome b (phox91-/-) was examined. Mycobacterium leprae multiplication in phox91-/- foot pads (FP) was elevated early in infection but subsequently arrested similarly to control mice within a noninvasive granuloma. Using a modified lepromin test model, a similar cellular composition in the M. leprae-induced FP granuloma in both strains with lymphocyte infiltration consisting primarily of CD4+CD44(hi)CD62L(lo) effector cells was found. Of great interest was the disparity in the T cell population between the granuloma and the draining lymph node which contained predominantly naïve CD4+CD44(lo)CD62L(hi) cells and was, therefore, not representative of the infection site. TH1 cytokines, chemokines and inducible nitric oxide synthase were comparably expressed in the FP of both strains. When infected in vitro, normal MPhi from B6 and phox91-/- mice supported bacterial viability, whereas IFNgamma-activated MPhi killed M. leprae in a RNI-dependent manner, emphasizing that ROI was dispensable. These data show that phox91-/- mice generate a strong adaptive immune response and control long-term infection with M. leprae.

Intradermal tests in dermatology-II: Tests for noninfectious diseases

INTRODUCTION Although the tests could be done at any site, the proximal part of the flexor aspect of the forearm is Intradermal tests are widely used to support the conventionally used. This site can be conveniently diagnosis of dermatological and nondermatological exposed and the skin of the proximal area is more diseases. They are mainly indicated for the detection sensitive than the distal. of immediate (Type I hypersensitivity) and delayed type hypersensitivity (DTH, Type IV hypersensitivity) INTERPRETATION OF INTRADERMAL TESTS towards exogenous or endogenous antigens. Intradermal tests for the diagnosis of infectious The optimal time for reading the reaction depends diseases in relevance to dermatovenereology are upon the pharmacological agent used for the test discussed in this section. and the type of immunological reaction to be observed. Intradermal tests for the detection of DTH Intradermal tests for the diagnosis of infectious are read at 48h, although they can be read as early diseases are listed in Table 1. They are indicated to as 12h and as late as four days. (The lepromin test detect DTH to organisms or their antigens. is read at four weeks and depends on the formation of a granuloma, which is a measure of cell-mediated Before undertaking intradermal test, it is advisable to immunity.) The size of the induration is more stop or avoid systemic steroids or immunosuppressive important than erythema while interpreting Type agents at least three days before the procedure as IV hypersensitivity. moderate to large doses of corticosteroids may inhibit a DTH reaction.

Intradermal tests in dermatology-I: Tests for infectious diseases

INTRODUCTION Although the tests could be done at any site, the proximal part of the flexor aspect of the forearm is Intradermal tests are widely used to support the conventionally used. This site can be conveniently diagnosis of dermatological and nondermatological exposed and the skin of the proximal area is more diseases. They are mainly indicated for the detection sensitive than the distal. of immediate (Type I hypersensitivity) and delayed type hypersensitivity (DTH, Type IV hypersensitivity) INTERPRETATION OF INTRADERMAL TESTS towards exogenous or endogenous antigens. Intradermal tests for the diagnosis of infectious The optimal time for reading the reaction depends diseases in relevance to dermatovenereology are upon the pharmacological agent used for the test discussed in this section. and the type of immunological reaction to be observed. Intradermal tests for the detection of DTH Intradermal tests for the diagnosis of infectious are read at 48h, although they can be read as early diseases are listed in Table 1. They are indicated to as 12h and as late as four days. (The lepromin test detect DTH to organisms or their antigens. is read at four weeks and depends on the formation of a granuloma, which is a measure of cell-mediated Before undertaking intradermal test, it is advisable to immunity.) The size of the induration is more stop or avoid systemic steroids or immunosuppressive important than erythema while interpreting Type agents at least three days before the procedure as IV hypersensitivity. moderate to large doses of corticosteroids may inhibit a DTH reaction.

Comparison between anti-PGL-I serology and Mitsuda reaction: clinical reading, microscopic findings and immunohistochemical analysis

The lepromin test, serum IgM antibodies against Mycobacterium leprae and in situ observations of T cell subsets in biopsies of Mitsuda reaction using monoclonal antibodies were performed on 44 untreated leprosy patients belonging to various classifications of the disease. The Mitsuda reaction was accessed clinically and histologically after 28 days. Clinical reading and histological analysis of Mitsuda reaction showed good agreement. The high positivity in clinical reading correlated with compact granulomas in histology. There is a graduation of Mitsuda reaction that follows the immunological spectrum of the disease. The histological study of Mitsuda reaction is valuable to confirm the immunological condition in doubtful clinical reaction. Anti-PGL-I IgM levels correlated with disease classification, increasing from the tuberculoid towards the lepromatous pole of the disease spectrum. There was an inverse correlation between serum IgM antibody levels and clinical and histological reading of Mitsuda reaction. There were no statistical difference in quantities and distribution of CD4+ and CD8+ T cells in all Mitsuda reactions. The pattern of cellular content of Mitsuda reaction could not be related to the T cells.

Fine needle aspiration cytology (FNAC) of nerves in leprosy.

Leprosy is primarily a disease of the peripheral nerves and a technique that is simpler than nerve biopsy is required to evaluate nerve involvement, especially in pure neuritic (PN) leprosy. This study was designed to evaluate the role of FNAC of the nerve in the diagnosis and classification of leprosy. A prospective study was carried out on 25 patients with clinically active leprosy and at least one thickened peripheral sensory nerve. Nerve aspirates were evaluated by May-Grunwald-Giemsa and Fite's staining. Lepromin test, slit skin smears (SSS), skin biopsies (except PN cases) and nerve biopsies were performed and compared with FNAC. FNAC of nerve from 23 cases (92%) yielded diagnostic aspirates. Acid fast bacilli were observed in six cases by FNAC. FNAC and nerve pathology were equally comparable with the other parameters evaluated. Based on the results, cytological criteria were developed for interpreting nerve aspirates and the cases were classified as paucibacillary (18), BB (2), BL (2), LL (1) and non-diagnostic (2). All PN cases showed diagnostic paucibacillary type cytology. FNAC of the nerve yields diagnostic aspirates in leprosy comparable with nerve pathology and the proposed cytological criteria may be useful in classification of nerve aspirates.

A high incidence of viableMycobacterium lepraein post-MDT recurrent lesions in tuberculoid leprosy patients

and is used in practice particularly in tuberculoid (paucibacillary) cases presenting with freshactivity in old and/or appearance of new lesions after release from treatment. This is based onthe assumption that a delayed hypersensitivity type reaction to persisting dead bacterialproducts (antigen), causes late reversal reaction. The present study was carried out todetermine whether viable bacteria are present in recurrent lesions of tuberculoid andborderline tuberculoid leprosy cases. The type and activity of the lesions are assessedhistopathologically. The results obtained in a small group of 25 patients are presented in thispaper.Material and methodsTwenty-five skin lesional biopsies obtained from 25 cases of borderline tuberculoid (BT)leprosy referred to the Foundation between 1996 to 1998 and presenting with recurrentlesions 1–13 years after the release from treatment were studied histopathologically andalso tested for the presence of viable bacteria, using the standard mouse foot pad method.Only confirmed cases of tuberculoid leprosy with reliable treatment and follow up detailswere included in this study. For each patient, a detailed history was taken, includingpretreatment presenting symptoms, treatment details, reactions if any, followed by a clinicalcharting to record the old and the new skin lesions as well as nerve lesions. Skin smearsand lepromin testing were also done. A deep incision skin lesional biopsy was obtained froman active lesion, using local anaesthesia.

Skin test development in leprosy: progress with first-generation skin test antigens, and an approach to the second generation.

One of the most urgent needs from leprosy research is a test for infection. The lepromin test is not suitable as a diagnostic test for leprosy, and neither the Rees nor the Convit soluble antigens has appeared sufficiently specific. Because two new antigens, MLSA-LAM and MLCwA, may not fully meet the requirements for specificity, we have embarked upon the preparation of a second generation of skin test antigens. Size-fractionated cryptozoic proteins were prepared from M. leprae by electroelution from preoperative sodium dodecylsulphate-polyacrylamide gel electrophoresis, and individual fractions were probed with polyclonal and monoclonal antibody reagents to identify both known and novel proteins. In addition, immunological responses were assessed in M. leprae-sensitized guinea pigs against both crude subcellular fractions (cytosol, membrane, and soluble cell wall proteins) and the size-fractionated cytosolic proteins. A particularly promising subcellular fraction is the membrane fraction of M. leprae, which contains many proteins unique to the organism. Clinical trials of the M. leprae membrane proteins are now being planned.

Experience and lessons from the use of lepromin and Mycobacterium leprae-specific serology.

Skin testing with lepromin, which produces a delayed-type hypersensitivity reaction, has been used in the classification of leprosy, and a good correlation has been found between immunological status and the reaction to lepromin. In addition, the prognostic value of the lepromin test has been demonstrated. More recently, skin testing with two soluble antigens of Mycobacterium leprae showed no difference of the mean size of the reaction between household contacts and non-contacts, indicating that these antigens are not useful for the diagnosis of leprosy. This and other evidence points to the need for a better skin test antigen capable of detecting infection of individuals by M. leprae. Whereas serological assays for antibodies against both PGL-1 and the 35 kDa antigen of M. leprae have been found to yield positive results in 90-100% of patients with lepromatous (BL/LL) leprosy, these assays fail to identify 40-60% of patients with tuberculoid (BT/TT) leprosy, because of the presence of only an insignificant level of antibody against components of M. leprae in these patients' serum, although, in many BT patients, antibody signal could be detected in the local lesions. These data indicate that there remains a need for a specific diagnostic test for leprosy.

Study of gene probes in childhood leprosy.

The objective was to detect nucleic acids of M. leprae in skin lesions of leprosy patients and study the effect of treatment on these nucleic acids, using r-RNA gene probes, using a cross sectional study. The study was carried out at Department of Paediatrics, S.N. Medical College, Agra and Department of Microbiology, Central JALMA Institute for leprosy, Agra. The study included 32 cases of leprosy less than 16 years of age, divided into 3 groups viz. without treatment (12 cases), in middle of treatment (11 cases) and at the end of treatment (9 cases). All cases were subjected to a detailed history and thorough clinical examination. All of them had smear examination and lepromin test done and their skin biopsies were subjected to gene detection. Nucleic acids were isolated from skin biopsies of all cases by standard procedure. After dot blotting of these nucleic acids, they were hybridised with radioactive (p32) r-RNA probes. The results were interpreted after getting the X-ray films processed with background signals from controls. Majority of cases were between 13-16 years of age. As age advanced, the disease moved from tuberculoid end of spectrum towards lepromatous end (p < 0.05). Majority of paucibacillary (PB) cases were lepromin positive while majority of multibacillary (MB) cases were lepromin negative (p < 0.05). In specimens of untreated cases, 50% of PB specimens and 87.5% of MB specimens were positive for r-RNA probes. In multibacillary type 100% smear positive specimens and 67% smear negative specimens were positive for r-RNA probes. In patients during the middle of treatment positivity for r-RNA decreased and 20% of PB specimens and 16.6% MB specimens were positive. At the end of treatment (1 year for PB cases and 2 years for MB cases), the results of r-RNA were negative, which indicated that the treatment regimens used in the study were effective. This study supports the usefulness of r-RNA probes as a diagnostic and therapeutic tool in childhood leprosy.

Borderline--tuberculoid leprosy: clinical and immunological heterogeneity.

The authors analysed some immunological criteria in leprosy patients diagnosed as borderline tuberculoid by the presentation of different grades of skin lesions as well as different grades of nerve involvement. Only 50% of the patients presented a single skin lesion and 58% had none or only one affected nerve. Nineteen patients (39.6%) showed a positive lepromin reaction (induration > or = 5 mm). Patients with a positive skin test had a greater number of skin lesions when compared with patients with a negative lepromin test. Fifty-seven percent of the patients were found to be positive using a lymphoproliferation test (LTT) in response to Mycobacterium leprae antigens. Positive LTT results did not correlate with the number of skin lesions, but patients unresponsive to LTT had a lesser extent of nerve involvement. Four out of 18 patients (22%) released high IFN gamma levels in PBMC culture stimulated by M. leprae. (mean U/ml +/- SD = 142 +/- 72). All of these 4 patients presented only one skin lesion, although three of them had more than one affected nerve. Nineteen out of 21 patients (90.5%) showed no anti-PGL-1 antibodies in their serum. The low levels of anti-PGL-1 antibodies among these patients confirmed their tuberculoid background even in those with multiple skin lesions. These findings seem to attribute an important role to IFN gamma in restraining the spreading of the infection in the skin, but IFN gamma may have an opposite effect on the nerves. The potential pathological effects of IFN gamma during the delayed type of hypersensitivity can be related to its ability to synergise with other inflammatory cytokines such as TNF alpha, IL-1 beta, and others.

Prevention and Early Detection of Leprosy in Children

India with its 4 million cases of leprosy, accounts for one-third of the world's population of leprosy patients. One-fourth of them are below 15 years of age. We report a 5-year follow-up study of healthy children who were close contacts of leprosy patients, in order to: 1. detect subclinical infection and observe the development of overt disease by using the Fluorescent Leprosy Antibody Absorption Technique (FLA-ABS) and the lepromin test which assess the humoral and cell-mediated immunity (CMI), respectively; 2. evaluate the efficacy of dapsone as a chemoprophylactic agent in the 'at risk' contacts. Four-hundred-and-fifty-five healthy contacts were studied. Majority of the contacts of multibacillary patients (303) were FLA-ABS positive (75 percent) and lepromin negative (55 percent) showing that although most of them had been infected, the lepromin status was negative (P < 0.01). On the other hand, the majority of the contacts of paucibacillary patients (152) were lepromin positive (57 percent) (P < 0.05). Furthermore, only 61 percent of contacts of paucibacillary patients were FLA-ABS positive as compared to 75 percent of contacts of multibacillary patients demonstrating that the former had been exposed to a lesser quantum of infection (P < 0.05). On the basis of results of FLA-ABS and lepromin tests, these 455 contacts were classified into four groups, viz. Group I comprising children who were FLA-ABS positive and lepromin positive; Group II, who were FLA-ABS positive and lepromin negative; Group III, who were FLA-ABS negative and lepromin positive; and Group IV who were FLA-ABS negative and lepromin negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Indeterminate leprosy: a seroimmunological and histochemical evaluation.

An effort was made to differentiate indeterminate (IND) leprosy from other types of the paucibacillary (PB) group of leprosy and to identify among indeterminate leprosy cases those which may evolve to multibacillary (MB) leprosy, using serological, immunological and histochemical parameters. A total of 92 untreated, histologically classified (TT-19, BT-30, IND-32) patients, including 11 cases diagnosed as nonspecific dermatitis (NSD), which were clinically strongly suspected to be leprotic, were screened for antibodies against PGL-I, 35-kDa and LAM antigens. Lepromin tests and antigen demonstration in tissue by indirect immunoperoxidase staining were also carried out. Though a qualitative analysis did not differentiate, a quantitative analysis in terms of a cumulative index (CI) showed a higher antibody level amongst the indeterminate group of patients than the other groups included in PB leprosy. Also, the lepromin negative indeterminate group patients showed a higher CI than the lepromin positive cases, indicating that perhaps these may be the cases which may develop into MB leprosy. Thus, the semiquantification of antibody levels in the form of a CI may be a useful parameter to predict the possible evolution of a given case of indeterminate leprosy. Interestingly 64% of NSD cases had either antigen or antibody which indicated that they were probably cases of leprosy.

LOCALIZED LEPROMATOUS LEPROSY AND ITS RESPONSE TO CHEMO‐IMMUNOTHERAPY

This is an unusual presentation of lepromatous leprosy (LL) in a young boy, 12 years of age. The study forms part of a large scale immunotherapeutic trial with Mycobacterium w (M.w) antileprosy vaccine. The trial is being conducted in two major hospitals in New Delhi, India. This patient presented with three lesions: one on each forearm and the third on the left leg. He was classified initially as borderline tuberculoid leprosy. Slit-skin smears and histopathology from the lesions proved the diagnosis to be lepromatous leprosy with a bacterial index (BI) 6+. The initial lepromin test was negative. The patient was treated with chemo-immunotherapy (standard multidrug therapy and immunotherapy with Mycobacterium w vaccine). Investigations after 1 year (15 months) of multi-drug therapy and three doses of vaccine, showed a remarkable fall in the BI from 6 to 0 in the lesions, a lepromin positivity of 5 mm, and a histological upgrading from lepromatous leprosy to borderline tuberculoid. Immunologic studies at 15 months revealed a good LTT response and high levels of cytokines, specifically IL-2 and IFN-gamma. This report presents an LL patient with disease limited to a few sites. It stresses the importance of slit-smear and biopsy in all patients of leprosy, and it highlights the upgrading observed on administration of chemo-immunotherapy.

Pilot study to determine acceptability and ability of heat-killedMycobacterium lepraeplus BCG (HKML + BCG) vaccine to induce skin test conversion

Although local reactions, including erythema, induration and ulcers, appeared in every patient after the injection of the combined HKML+BCG vaccine, they were accepted by the patients. There was no tendency for the local reaction to become aggravated after repeated vaccination. However, systemic reactions, mainly iridocyclitis and complaint of numbness of the fingers and toes, became quite common after the 5th vaccination and therefore significantly reduced the acceptability of vaccine by injection. It seems that repeated vaccination might activate the iridocyclitis, but the relationship between the complaint of numbness and vaccination has not been well established. Neither typical ENL nor reversal reaction had been observed throughout the trial. A significant proportion of patients converted to SMLA positivity after repeated vaccination. However, it seems the positive status was not stable as many of them reverted to negative after the following vaccination. After the 7th vaccination, the positive conversion rate to SMLA-I was 45% and to SMLA-II was 35%. After the 8th vaccination, 66.7% of patients converted to Mitsuda reaction positive, which has been confirmed by histopathological examination. Nevertheless, further follow-up is required in order to determine whether or not such conversion will be of a long duration. The reactions to SMLA-I and SMLA-II were associated but only correlated at a moderate level. Overall, the positive conversion rate to SMLA-I was significantly higher than that to SMLA-II after repeated vaccination. Neither the early reaction nor the late (Mitsuda) reaction of the lepromin test were correlated to either SMLA reaction. The repeated vaccination of HKML+BCG vaccine did not affect the weakly-positive anti-PGL-1 Mycobacterium leprae antibody level seen in the skin-smear negative lepromatous patients participating in this study.

Neuritic leprosy: epidemiology and therapeutic responsiveness.

We studied epidemiology, progression and therapeutic responsiveness in 62 cases of neuritic leprosy. Numbness was the main presenting symptom. Mononeuritis involving the ulnar nerve, followed by the common peroneal nerve was the commonest presentation. The lepromin test was positive in 34 cases while a slit-skin smear was negative in all cases. We treated 20 of these cases with dapsone monotherapy and 5 cases (25%) developed a skin lesion after an average duration of 3 months' treatment. We treated 42 cases with a combination of dapsone and rifampicin, and 3 cases (7%) developed a skin lesion after an average duration of 2-6 months. The subsequent diagnosis in cases developing skin lesions was borderline--lepromatous in 1 case, borderline-tuberculoid in 4 cases, tuberculoid in 2 cases and indeterminate in 1 case.

Early Detection of Leprosy in Children

Healthy children contacts of leprosy patients had their humoral and cell-mediated immunological status assessed using the Fluorescent Leprosy Antibody Absorption Technique (FLA-ABS) and the Lepromin test, respectively. Subsequently, they were followed up for 2 1/2 years to study the development of overt disease. Two-hundred children were studied and classified into four groups, viz. Group I comprised of children who were FLA-ABS positive and Lepromin positive; Group II = FLA-ABS positive and Lepromin negative; Group III = FLA-ABS negative and Lepromin positive; Group IV = FLA-ABS negative and Lepromin negative. The good cell-mediated immune (CMI) response in the 107 children in Group I prevented them from developing the disease though they had been infected. Out of the 37 children in Group II, 15 developed the disease. There were no children in Group III. None of the 56 children in Group IV developed the disease, possibly because they had not been significantly infected. All these findings were statistically significant (P less than 0.01). This study highlights the protective role of cell-mediated immunity in leprosy. It also suggests the need to carry out surveillance surveys in the endemic population to identify and follow up those at risk.

Risk factors for type-1 reactions in borderline leprosy patients

Type-1 or reversal reactions are the major cause of nerve damage and disability in leprosy. We wished to determine whether there were any clinical or laboratory markers that identified patients with an increased risk of type-1 reaction. 42 (31%) of 136 Nepalese borderline leprosy patients (97 male, 39 female; age range 7-73 years) had a type-1 reaction during the first 2 years of multi-drug therapy. Before therapy, 41 (98%) of the 42 patients were seropositive for antibodies to one of three mycobacterial antigens. Seropositivity for IgM anti-phenolic-glycolipid-1 (PGL-1) antibodies, but not IgG anti-lipoarabinomannan or anti-Mycobacterium leprae 35 kDa protein antibodies, was significantly associated with subsequent manifestation of a type-1 reaction (p<0·001). The concentration of IgM anti-PGL-1 antibodies in serum was significantly higher in patients in whom a type-1 reaction developed. The risk attributable to anti-PGL-1 seropositivity was independent of leprosy class, skin smear positivity, and the presence of other anti-M leprae antibodies (adjusted odds ratio=8·7, p<0·001). In the 87 patients who had a lepromin test, anti-PGL-1 seropositivity and lepromin reactivity were significant independent risk factors for subsequent reaction. 78% of patients with positive lepromin reactivity and IgM anti-PGL-1 antibodies had type-1 reactions. Patients with these risk factors should be carefully monitored during antimicrobial therapy to permit early initiation of anti-inflammatory treatment thus minimising permanent nerve damage and resultant disability.