January/February 2012 • Volume 10 • Issue 1 - SKINmed Journal

January/February 2012 Volume 10 • Issue 1
Tuberculosis (TB) is a common disease worldwide, 1
and its clinical incidence has been impacted by the
emergence of the human immunodeficiency virus
(HIV), increased transmigration from endemic countries,
and its transmission in health care facilities, prisons, homeless
shelters, and other crowded settings. 2–5 TB is largely an airborne
infection; however, skin manifestations may be caused
by hematogenous spread or the contiguity from latent and/or
active foci of infection. Primary inoculation, although uncommon,
is another known mode of transmission. HIV infection,
intravenous drug abuse, diabetes mellitus, immunosuppressive
therapy, malignancies, end-stage renal disease, and infancy may
predispose to TB. Although cutaneous TB (CTB) is a well-
recognized clinical entity, it often poses a diagnostic dilemma
for physicians 6 ; therefore, it is important to perform a careful
review of clinical presentations in each patient, which may prove
predictive of its diagnosis. 7,8
CLASSIFICATION
The most widely accepted CTB classification is based on the
route of infection. 6,9 Exogenous inoculation occurs after the
direct inoculation of Mycobacterium tuberculosis into the skin of a
person who is susceptible to infection (vide infra). This may cause
TB verrucosa cutis (TBVC), TB chancre, and some cases of lupus
vulgaris (LV), whereas endogenous infection is caused by either
lymphatic or hematogenous spread or a contiguous extension.
Occasionally, lymphatic spread is seen in LV. Hematogenous
spread, on the other hand, is responsible for acute miliary TB,
metastatic tubercular abscess, gummatous TB, papulonecrotic
tuberculid (PNT), and lupus vugaris. Contiguous extension
CORE CURRICULUM
Virendra N. Sehgal, MD, Section Editor
Cutaneous Tuberculosis: A Diagnostic Dilemma
Virendra N. Sehgal, MD; 1 Prashant Verma, MD; 2 Sambit N. Bhattacharya, MD; 2 Sonal Sharma, MD; 3
Navjeevan Singh, MD; 3 Nishant Verma, MD 4
Cutaneous tuberculosis continues to be one of the most difficult conditions to diagnose. It is a challenge particularly in developing
countries due to the lack of resources. The authors define the classification and clinical manifestations considered predictive of its diagnosis.
from the underlying lesion is a characteristic feature of both
scrofuloderma and TB cutis orificialis (TBCO).
In attempt to embellish the preceding classification, it has been
divided into multibacillary and paucibacillary variants based on
the bacterial load. The former is recognized by the characteristic
morphology of the organism in the tissue sections stained
with Ziehl-Neelsen method, complemented by in vitro recovery
of M tuberculosis, while sparse bacilli on histological examination
and rare in vitro culture isolation 2 identify the latter.
Unfortunately, it is difficult to distinguish the organisms in
paucibacillary TB.
CLINICAL FEATURES
Although the prevalence of CTB accounts for 1.5% of all cases
of TB, it is, nevertheless, important to consider the entity when
patients present with a suggestive clinical morphology. CTB has
many forms, including multibacillary and paucibacillary CTB,
which are defined in detail below.
MULTIBACILLARY CTB
TB CHANCRE/INOCULATION TB
Tuberculous chancre (primary inoculation TB) is a variant of
multibacillary CTB that results from direct introduction of
mycobacteria into the skin or mucosa of an individual who neither
had tubercular infection in the past nor was immunized
with Bacille Calmette-Guérin (BCG). Trauma also facilitates the
entry of the organism into the skin. 10,11
Face and other exposed areas are vulnerable sites of introduction.
The organism multiplies in tissue macrophages and migrates to
From the Dermato-Venereology (Skin/VD) Center, Sehgal Nursing Home, Panchwati, Delhi; 1 the Departments of Dermatology and STD2 and
Pathology, 3 University College of Medical Sciences and Associated Guru Teg Bahadur Hospital, Delhi; and the Department of Microbiology,
Maulana Azad Medical College and Associated Chacha Nehru Bal Chikitsalaya, Delhi, 4 India
Address for Correspondence: Virendra N. Sehgal, MD, Dermato-Venerology (Skin/VD) Center, Sehgal Nursing Home, A/6 Panchwati, Delhi
110 033 India • E-mail: drsehgal@ndf.vsnl.net.in
SKINmed. 2012;10:28–33 28
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