00:01
Welcome to our lecture on cutaneous
tuberculosis or skin TB.
00:07
Cutaneous tuberculosis is invasion of the
skin by Mycobacterium
tuberculosis complex. It's relatively
uncommon,
but it does occur. Extrapulmonary
TB constitutes 15% of all cases,
and
cutaneous lesions account for less than 2% of
all extrapulmonary
manifestations. So we know that the most
common type of TB is
pulmonary TB. So now let's look at the
etiology of
cutaneous TB. This is caused by gram
positive rod shaped bacilli as listed.
00:52
So how do we classify cutaneous TB.
00:56
There's true cutaneous tuberculosis one.
00:59
Secondly, the tuberculids.
01:02
The tuberculids are a result of
hypersensitivity reaction to
mycobacteria that is not detectable,
whereas in true
cutaneous tuberculosis there's mycobacteria
which can be
identified in the areas of cutaneous TB.
01:18
So one gets contiguous spread or
autoinoculation,
and it can present as scrofulodema or TB
cutis
or orificialis. If there's hematogenous
spread to the
skin, you can get cutaneous TB presenting as
lupus
vulgaris, miliary TB,
or metastatic
tuberculosis abscess. Through inoculation
from
exogenous source, then you get primary
inoculation
which presents as TB verrucosa cutis or TB
chancre.
01:57
Looking at now the tuberculids remember we
mentioned that tuberculids is an
ID reaction. It's a hypersensitivity reaction
to the TB,
but you cannot identify the TB in the lesion.
02:08
So what are the types of tuberculids?
Erythema nodosum which is the most common
presentation.
02:15
Erythema in duratom of basin or just erythema
in duratom.
02:19
And what we call papular necrotic tuberculoid
or PNT.
02:24
Lichen scrofulaceum, which is more common in
children.
02:28
Now let's now focus on the individual types
of cutaneous TB.
02:32
We want to start with scrofulo derma.
02:34
This results from direct extension of an
underlying TB focus
could be a regional lymph node or infected
bone or joint.
02:42
And then you get spread to the surface.
02:46
And this presents with firm,
painless lesions that eventually ulcerate
with a granular base. It may heal even
without treatment,
but it takes years and leaves unsightly
scars.
02:59
So if again focus on scrofuloderma and look
at the differential of
scrofuloderma. Remember we're talking about
the different types of TB.
03:08
We're starting with scrofuloderma and its
differentials.
03:11
So the differential of scrofuloderma is
bacterial abscess
a condition called hidradenitis suppurativa
which has become quite
common in the recent years and common in
patients who are overweight.
03:26
And the other differential is gummatous
syphilis.
03:30
Moving on now to the second type it's lupus
vulgaris.
03:36
Lupus vulgaris, you get sharply defined
grayish brown nodules
with a gelatinous consistency.
03:42
You don't see the erythema.
03:44
Erythema that's classical in white patients.
03:47
It affects primarily the head and neck and
persists for years,
leading to disfigurement and skin cancer in
some cases.
03:58
The differential of lupus vulgaris includes
other forms of cutaneous TB,
for example, tuberculosis verrucosa cutis.
04:08
The second differential is deep fungal
infections,
for example histoplasmosis
and of course lepromatous leprosy can be also
confused
with lupus vulgaris.
04:25
Leishmaniasis is another condition which is
seen commonly in South America,
and it's a big differential in that area
where it is
endemic for lupus vulgaris.
04:38
Other differentials for lupus vulgaris
include sarcoidosis and Wegener's
granulomatosis.
04:48
So moving on to tuberculosis.
04:52
This is a hypersensitivity reaction due to
circulating
Mycobacterium tuberculosis or its antigens.
05:02
The first one that we're going to talk about
is erythema nodosum.
05:06
It is the most common tuberculoid,
and it presents with bilateral tender,
erythematous subcutaneous nodules ranging
from 3 to 20cm.
05:17
It tends to occur on the arms,
knees, lower legs,
sometimes on the face and neck,
but this is very rare,
if it when it affects the face and neck.
05:29
So what are the differentials of erythema
nodosum erythema induratum of
basin which is another type of Id reaction or
hypersensitivity
reaction. Cutaneous polyarteritis nodosa,
which is a connective tissue
disorder, is another differential for
erythema nodosum,
and of course superficial thrombophlebitis is
a differential
for erythema nodosum. The next type of
id reaction is erythema induratum of bazin.
06:03
Here one gets recurrent nodules or lumps,
and they tend to be
bigger than those of erythema nodosum.
06:11
Same year it tends to occur in lower legs,
particularly young women.
06:17
It may ulcerate and scar,
and the differential involves erythema
nodosum and cutaneous polyarteritis nodosa,
and of course,
cutaneous lymphoma. The next step of
tuberculin
is what we call P N T,
papulo necrotic tuberculin.
06:36
In these patients, you see multiple recurrent
hypopigmented crusted papules.
06:43
The papules can become pustular or necrotic,
resulting in small ulcers
and scars after healing.
06:53
Typically heals with varioli form,
chickenpox like scarring after about
six weeks. And it tends to occur on the upper
limbs and on the lower
limbs. The differential diagnosis includes
leukocytoclastic
vasculitis, papular eczema,
and prurigo
simplex. The last one,
lichen scrofulosorum,
is another id reaction.
07:19
It's a lichenoid eruption of minute papules,
hence the name lichen
and papules are usually asymptomatic.
07:27
They are closely grouped and their skin
colored to brown color.
07:33
The differential of lichen scrofulosorum is
lichen
nitidus, which is usually asymptomatic,
and another one is
keratosis pilaris, which is quite common and
sometimes associated with
atopic eczema. So what are some of the
complications of these
conditions? Dissemination is very rare and
one m ay
get scarring. How do we diagnose the skin,
cutaneous
TB? The history and physical examination is
important,
and immunologic tests are done,
for example,
the mantoux or tuberculin skin test,
which is a delayed hypersensitivity
reaction, is positive in patients with skin
TB.
08:17
We also offer the interferon gamma release
assays to
see whether the patient has been exposed to
TB.
08:25
Mycobacterial culture remains the gold
standard for non-tuberculous
lesions, but in the id reaction that you're
not going to find
anything because it's a hypersensitivity
reaction.
08:39
The skin biopsy is also an important
investigation that we have to do
where we suspect cutaneous TB.
08:48
And it's also important to trace the contacts
of family members
of patients with TB.
08:58
What about management?
The treatment of TB is the standard anti-TB
therapy which includes
rifampicin, isoniazid,
pyrazinamide and ethambutol .
09:09
And we use a nice mnemonic RIPE therapy so
you don't forget.
09:14
So there's two phases.
09:16
The first phase is intensive phase where
there's two months of all four
anti-TB treatment. This is then followed by
the maintenance
phase which includes four months of only
rifampicin
and isoniazid. And of course it's important
in black
patients because of the scarring and
post-inflammatory hyperpigmentation to
ensure that you offer treatment for patients
for a holistic approach
to anti TB medication.
The lecture Cutaneous Tuberculosis in Darker Skin by Ncoza Dlova is from the course Bacterial Skin Infections in Patients with Darker Skin.
Which of the following is the key difference between true cutaneous tuberculosis and tuberculids?
Which form of cutaneous tuberculosis results from hematogenous spread to the skin?
A patient presents with recurrent multiple lower extremity dark papular lesions, some of which have become pustular. Pathology showed tuberculoid granulomatous inflammation but smears and culture were negative. What is the diagnosis?
Which test remains the gold standard for diagnosing non-tuberculid cutaneous lesions?
Which characteristic feature is associated with lupus vulgaris?
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