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Lobomycosis is a cutaneous mycosis
characterized by a slowly developing variably sized cutaneous nodules
after a traumatic event.
Lacazia loboi
( Syn: Loboa loboi ) the etiologic agent, cannot be grown in culture.
The lesions are
composed of granulomatous inflammatory tissue containing
numerous globose or subglobose to lemon-shaped, yeast-like
fungal cells singly or in simple and branched
chains.
Natural infection occurs only in human
and dolphins and produces locally enlarging cutaneous nodules that
become verrucous.
Cases of
lobomycosis involving two species of dolphins, namely,
marine dolphins (Tursiops truncatus) and marine freshwater
dolphins (Sotalia fluviatilis) , have been reported.
Clinical history:
The onset of the disease is generally insidious. The increase
in size or number of lesions is a slow process, progressing over
a period of 40 to 50 years . The history often
reveals the cause being a trauma, for example, an arthropod
sting, a snake bite, a cut from an instrument, or a wound acquired
while cutting vegetation. The causal agent of lobomycosis
appears to be in aquatic environments, which probably plays
an extremely significant part in its life cycle
Geographic distribution:
The
human disease is endemic in the tropical zone of the New World and has
been reported in central and western Brazil, Bolivia,
Colombia, Costa Rica, Ecuador, Guyana, French Guiana, Mexico,
Panama, Peru, Suriname, and Venezuela.
Pathological
features:
The dermal
nodules manifest as either smooth, verrucose, or ulcerated
surfaces which can attain the size of a small
cauliflower-like keloid.
Image Link.
The yeast-like cells of L. loboi are
abundant in the dermis of the cutaneous nodules.
These thick-walled cells, 6
to 12 micrometer in diameter, are remarkably uniform in size and
shape.
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They reproduce by progressive budding
in chains, three to eight cells in length, each of which resembles a
“string of pearls”.
Adjacent cells are connected to one
another by tube-like isthmuses, and secondary budding may be observed.
Nonbudding and single-budding cells are
also present.
The surrounding dermis contains a
dispersed epitheloid and giant cell granulomatous inflammatory
reaction.
Diagnosis:
Diagnosis
is based on demonstrating the presence of globose,
thick-walled yeast-like cells in lesion exudate or tissue
sections. The organism multiplies by budding, and thus
mother cells with single buds are often observed.
These thick-walled, hyaline, spherical cells with chains of
cells interconnected by tubular connections are the basis
on which a diagnosis of lobomycosis rests. The thick-walled,
budding hyaline cells with chains of conidia can be readily
observed in tissue smears or exudates mounted in 10% KOH or in
Calcofluor mounts.
Treatment:
The lesions are best treated by surgical excision.
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