Page 198 - Textbook of Pathology, 6th Edition

182 MYCETOMA
Mycetoma is a chronic suppurative infection involving a
limb, shoulder or other tissues and is characterised by
draining sinuses. The material discharged from the sinuses
is in the form of grains consisting of colonies of fungi or
bacteria. Mycetomas are of 2 main types:
Mycetomas caused by actinomyces (higher bacteria)
comprising about 60% of cases (page 163).
SECTION I
Eumycetomas caused by true fungi comprising the
remaining 40% of the cases.
Most common fungi causative for eumycetoma are
Madurella mycetomatis or Madurella grisea, both causing black
granules from discharging sinuses. Eumycetomas are
particularly common in Northern and tropical Africa,
Southern Asia and tropical America. The organisms are
inoculated directly from soil into barefeet, from carrying of
contaminated sacks on the shoulders, and into the hands from
infected vegetation.
Figure 7.8 Candidiasis of the ulcer in the skin.
MORPHOLOGIC FEATURES. After several months of
infection, the affected site, most commonly foot, is swollen Various predisposing factors are: impaired immunity,
and hence the name ‘madura foot’. The lesions extend prolonged use of oral contraceptives, long-term antibiotic
deeply into the subcutaneous tissues, along the fascia and therapy, corticosteroid therapy, diabetes mellitus, obesity,
eventually invade the bones. They drain through sinus pregnancy etc.
tracts which discharge purulent material and grains. The
surrounding tissue shows granulomatous reaction MORPHOLOGIC FEATURES. Candida produces super-
(Fig. 7.7). ficial infections of the skin and mucous membranes, or
may invade deeper tissues as described under:
CANDIDIASIS 1. Oral thrush. This is the commonest form of muco-
General Pathology and Basic Techniques
Candidiasis is an opportunistic fungal infection caused most cutaneous candidiasis seen especially in early life. Full-
commonly by Candida albicans and occasionally by Candida fledged lesions consist of creamy white pseudomembrane
tropicalis. In human beings, Candida species are present as composed of fungi covering the tongue, soft palate, and
normal flora of the skin and mucocutaneous areas, intestines buccal mucosa. In severe cases, ulceration may be seen.
and vagina. The organism becomes pathogenic when the 2. Candidal vaginitis. Vaginal candidiasis or monilial
balance between the host and the organism is disturbed. vaginitis is characterised clinically by thick, yellow, curdy
discharge. The lesions form pseudomembrane of fungi on
the vaginal mucosa. They are quite pruritic and may
extend to involve the vulva (vulvovaginitis) and the
perineum.
3. Cutaneous candidiasis. Candidal involvement of nail
folds producing change in the shape of nail plate
(paronychia) and colonisation in the intertriginous areas
of the skin, axilla, groin, infra- and inter-mammary,
intergluteal folds and interdigital spaces are some of the
common forms of cutaneous lesions caused by Candida
albicans (Fig. 7.8).
4. Systemic candidiasis. Invasive candidiasis is rare and
is usually a terminal event of an underlying disorder
associated with impaired immune system. The organisms
gain entry into the body through an ulcerative lesion on
the skin and mucosa or may be introduced by iatrogenic
means such as via intravenous infusion, peritoneal dialysis
or urinary catheterisation. The lesions of systemic
candidiasis are most commonly encountered in kidneys
as ascending pyelonephritis and in heart as candidal
Figure 7.7 Madura foot. Brown granule lying in necrotic tissue in endocarditis.
the discharging sinus.