|Year : 2001 | Volume
| Issue : 4 | Page : 193-196
Clinical and morphological variants of cutaneous tuberculosis and its relation to mycobacterium species
R Gopinathan, D Pandit, J Joshi, H Jerajani, M Mathur
Department of Microbiology, LTM Medical College and General Hospital, Sion, Mumbai - 400 022, India
Department of Microbiology, LTM Medical College and General Hospital, Sion, Mumbai - 400 022, India
Cutaneous tuberculosis forms a small proportion of extrapulmonary tuberculosis. The incidence of cutaneous tuberculosis has fallen from 2% to 0.15% in India whereas it is rare in developed countries. The present study is an attempt at finding out the Mycobacterium species associated with cutaneous tuberculosis. A total of 51 cases of clinically suspected cutaneous tuberculosis were studied over a period of 18 months from July 1997 to December 1998. Of these, 32 (62.75%) were Scrofuloderma cases, 12 (23.52%) cases of Lupus vulgaris and 7 (13.73%) were Tuberculosis verrucosa cutis (TBVC) cases. Twenty nine mycobacterial isolates from 51 specimens gave an isolation rate of 56.86%. These were subjected to a battery of biochemical tests for identification to species level. Twenty six out of 29 isolates were identified as Mycobacterium tuberculosis, two were identified as Mycobacterium Scrofulaceum and one Mycobacterium avium complex was isolated. Sixteen Mycobacterial isolates were recovered from Scrofuloderma cases, 9 were isolated from Lupus vulgaris and 4 from TBVC cases. The three atypical mycobacterial isolates were recovered from Scrofuloderma cases. Though Mycobacterium tuberculosis was the most common isolate, Mycobacterium scrofulaceum and Mycobacterium avium complex were also isolated in the present study.
|How to cite this article:|
Gopinathan R, Pandit D, Joshi J, Jerajani H, Mathur M. Clinical and morphological variants of cutaneous tuberculosis and its relation to mycobacterium species. Indian J Med Microbiol 2001;19:193-6
|How to cite this URL:|
Gopinathan R, Pandit D, Joshi J, Jerajani H, Mathur M. Clinical and morphological variants of cutaneous tuberculosis and its relation to mycobacterium species. Indian J Med Microbiol [serial online] 2001 [cited 2016 May 31];19:193-6. Available from: http://www.ijmm.org/text.asp?2001/19/4/193/8188
The organism responsible for tuberculosis was identified and diagnostic skin tests were developed more than 100 years ago, a tuberculosis vaccine has been in use for over 60 years and chemotherapy for over 30 years. Despite all these, tuberculosis still remains a major international health problem. The invasion of the skin by Mycobacterium tuberculosis has become a rare event in developed countries. In developing country like India, the incidence has fallen from 2% to 0.15%. This decline in incidence may be attributed to the availability of effective antitubercular drugs, elimination of milk-herds and general improvement in the living standards.
But in the present scenario, the disease is fast reappearing due to the HIV pandemic and due to emerging resistance to the conventional treatment. The aetiology in most forms of cutaneous tuberculosis is reported to be Mycobacterium tuberculosis and Mycobacterium bovis, but in bizarre forms of cutaneous tuberculosis seen in HIV infected individuals, atypical saprophytic strains of Mycobacterium have also been implicated.
The present study attempts at finding out the prevailing strains of Mycobacteria both M. tuberculosis and Atypical Mycobacteria in the Scrofuloderma, Lupus vulgaris and Tuberculosis verrucosa cutis (TBVC) cases of cutaneous tuberculosis encountered in LTMMC and LTMGH, Sion.
| ~ Materials and Methods|| |
Fifty one clinically suspected cases of cutaneous tuberculosis were studied over a period of 18 months from July 1997 to December 1998. Out of these, 35 skin biopsy specimens and 16 tissue exudates were collected and processed. Skin biopsies were sampled by 5mm punch biopsy performed on the active advancing edge of the lesion under aseptic conditions and were transported in sterile petridishes. These were immediately ground using sterile pestle and mortar in 0.2% Bovine albumin., The ground tissue was used for making smears to be stained by Ziehl Neelsen's staining method and for inoculating on Lowenstein Jensen's slants.
Tissue exudates were aspirated using sterile needles and syringes. In cases of discharging sinuses, tissue exudates were sampled by means of sterile cotton swabs. Two swabs were collected for culture and smears. Histopathological studies were conducted for all the specimens.
Lowenstein Jensen slants were incubated at 370C and 250C. The slants were examined for growth every week for 8 weeks. The presence of acid fast bacilli was confirmed by Ziehl Neelsen's staining of the growths.
The pure isolated growth on Lowenstein Jensen medium were identified to species level using rate of growth, pigment production and results of biochemical tests like Niacin, Nitrate reduction, Aryl sulphatase, Urease, Pyrazinamidase, Tween hydrolysis and semiquantitative and heat stable catalase tests.
| ~ Results|| |
As shown in [Table - 1], out of 51 clinically suspected cases of cutaneous tuberculosis studied, 32 were scrofuloderma, 12 were Lupus vulgaris and 7 Tuberculosis verrucosa cutis (TBVC). Tissue exudates were recovered only from Scrofuloderma cases.
Demonstration of acid fast bacilli was possible in tissue exudates in 5 Scrofuloderma cases. It was not possible to demonstrate acid fast bacilli in other morphological variants [Table - 2].
Recovery of acid fast bacilli in culture was encountered in 29 cases (56.86%). The clinical morphological variant wise distribution of recovery of acid fast bacilli in culture showed that 16 isolates were recovered from 32 (50%) cases of Scrofuloderma, 9 from 12 (75%) cases of Lupus vulgaris and 4 from 7 (51.14%) cases of TBVC [Table - 3].
All the recovered acid fast bacilli when subjected to biochemical tests revealed that out of 29 strains, 26 were M. tuberculosis and 3 were atypical mycobacteria. The atypical mycobacteria were isolated from Scrofuloderma cases. Of the 3 atypical mycobacteria, 2 were Mycobacterium scrofulaceum and one was Mycobacterium avium complex [Table - 4].
In the 29 cases of cutaneous tuberculosis, where recovery of acid fast bacilli was possible, histopathological picture supported the clinical diagnosis. In cases of Lupus vulgaris, granulomatous infiltrate of the tuberculoid type consisting of epitheloid cells, lymphocytes and plasma cells with giant cells especially Langhan's giant cells were seen in dermis. Caseation was absent except in one case. In TBVC, dermal granulomas with Langhan's giant cells were seen in all the cases whereas caseation was seen in only two cases. Scrofuloderma showed granulomatous infiltrate with Langhan's giant cells and caseation in dermis extending all the way to subcutaneous tissue. Even Scrofuloderma like lesions caused by M.avium complex and M.scrofulaceum showed tuberculoid granulomatous lesion histopathologically.
| ~ Discussion|| |
Cutaneous tuberculosis has a worldwide distribution. In the past, it was more prevalent in temperate countries with cold and humid climate with few hours of daily sunlight but now it is being encountered in tropical countries like India.
Malnutrition and low socioeconomic conditions are predisposing factors for cutaneous tuberculosis. Two decades back a decline was observed in the incidence of cutaneous tuberculosis, but recently there is resurgence of cutaneous tuberculosis due to multidrug resistant strains of Mycobacterium tuberculosis.
Though human disease with Mycobacterium tuberculosis and M.bovis is usually spread by droplets and the portal of entry is often the respiratory tract, skin can also be primarily involved. Lupus vulgaris occurs mainly in patients with moderate or high degree of immunity. The lesion arises due to inoculation by exogenous source and by hematogenous spread. Scrofuloderma manifests after the breakdown of the skin overlying a tuberculous focus usually a lymph node but sometimes an infected bone or joint. A patient with moderate or high degree of immunity can develop TBVC if accidental superinfection from extraneous source and autoinocualtion or post-traumatic inoculation with infected sputa occurs.
In the present study, out of 51 clinically suspected cases of cutaneous tuberculosis, Scrofuloderma formed the largest group as also reported by other workers., 23.52% cases belonged to Lupus vulgaris and 13.73% cases were of TBVC. Scrofuloderma accounted for the largest number of cases (62.75%).
Demonstration of acid fast bacilli in tissue smears by Ziehl Neelsen's staining was possible in 5/51 (9.8%) cases. This conforms with study by Sehgal et al  in which 9.52% cases were smear positive. As opined by Montgomery7 and Sehgal et al , it was easy to demonstrate acid fast bacilli in tissue smears in cases of Scrofuloderma. Tissue exudates were found to be better clinical specimens for detection of acid fast bacilli whenever possible as in case of Scrofuloderma cases.
Acid fast bacilli were recovered from 7% to 55% of the cases of cutaneous tuberculosis by various workers.,, 56.86% of recovery rate reported in present study is in accordance with that reported by Quiros et al. The wide difference in the recovery rate may be due to different clinical materials studied in different ways. It was found that tissue exudates from the lesions of Scrofuloderma yielded better isolation of Mycobacteria (75%) whereas skin biopsy even after homogenization with 0.2% bovine albumin without decontamination gave 45.71% isolation.
Recovery of acid fast bacilli was possible in 50% cases of Scrofuloderma, 75% cases of Lupus vulgaris and 57.14% cases of TBVC. Two other studies had 52% and 50% isolation rates from cases of Lupus vulgaris respectively.
In 7.84% cases, it was possible to both demonstrate and recover acid fast bacilli from clinical specimens of cutaneous tuberculosis. In 49.0%, it was possible to only recover the bacilli whereas demonstration in primary smear was not possible. In one case out of 51, where the patient was treated with antituberculosis drugs of Isoniazid, Rifampicin, Pyrazinamide and Ethambutol, acid fast bacilli were seen in the smear but not isolated in culture. This can be explained as the nonviability of the organism due to prior treatment.
Twenty six out of 29 cases, where Mycobacterium spp. were isolated, were Mycobacterium tuberculosis (89.65%). Two out of 3 atypical Mycobacteria were M.scrofulaceum and one was M.avium complex. One M.scrofulaceum and the M.avium complex isolates were recovered from two different immunocompromised patients. This has also been cited by Murray et al, 12 Lombardo et al, and Villas F et al who have isolated M.scrofulaceum and M.avium complex from skin lesions in immunocompromised patients. However one isolate of M.scrofulaceum was isolated from a 10 year old immunocompetent patient having cervical adenitis.
Thus, M.tuberculosis was the most common aetiological agent of cutaneous tuberculosis in the morphological variants of Scrofuloderma, Lupus vulgaris and TBVC in the present study though M.scrofulaceum and M.avium complex were also isolated from Scrofuloderma cases which was the most common clinical morphological variant encountered.
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