Skin
infections
Staphylococcal
infections
Most skin infections are staphylococcal and relatively minor. They will
settle with no specific treatment; topical antiseptics may be used or systemic
antibiotics if the infection does not settle or spreads. Patients with
unexplained infections should be checked for diabetes mellitus. The sensitivity
of the organisms is determined so that the appropriate antibiotic can be chosen
should the need arise. Incision and drainage are indicated when pus is present.
If severe, lyrnphangitis or cellulitis can develop. Various clinical
presentations exist.
Boil (syn. furuncle) is an infection of a pilosebaceous unit with
perifolliculitis, which usually proceeds to suppuration and central necrosis. A
‘blind boil’ is one that subsides without suppuration. Boils are common on
the face, head and neck. Boils are frequently associated with overwork, worry,
debility or other undermining influences. They may be the presenting symptom of
diabetes mellitus.
Furunculosis
of the external auditory meatus is extremely painful, as the skin is attached to
the underlying cartilage, and swelling is accompanied by considerable tension.
Stye
(syn. hordeolum) is due to infection of an eyelash follicle. Should
softening occur around a hair follicle, particularly an eyelash, removal of the
hair allows the pus to escape.
Carbuncle4
is an infective gangrene of the subcutaneous tissues, which often occurs
in the nape of the neck. The subcutaneous tissues become painful and indurated,
and the overlying skin is red (Fig. 13.9). Unless the condition is aborted by
prompt treatment, extension will occur and, after a few days, areas of softening
appear, the skin sloughs and discharges pus. Usually there is one central large
slough, surrounded by a ‘rosette’ of smaller areas of necrosis. The general
treatment and organism identification are similar to those described for boils.
Many carbuncles are aborted if antibiotics are used adequately in the early
stages.
Impetigo
is an intradermal infection (Fig. 13.10). The primary lesion is bullous, and
soon ruptures to form an erosion and then a crust. The
4’Carbunculus’
in Latin, ‘anthrax’ in Greek, is the word for charcoal. The ancients saw in
these conditions burning sores upon the skin —
hence they likened them to glowing coal.
infection is contagious, and in rugby football one player so infected
can spread the disease among team mates and the opposing side (the condition
being known as scrumpox). Treatment is by careful washing of the face to remove
crusts using chlorhexidine soap and lotion (1 per cent); systemic antibiotics
are used in those cases that are resistant to local treatment.
Necrotising
fasciitis (syn. Meleney’s
streptococcal
gangrene, Fournier’s gangrene)
Necrotising fasciitis is a destructive invasive infection of skin,
subcutaneous tissue and deep fascia, with relative sparing of muscle.
Bacteriology can be polymicrobial involving a synergistic combination of
anaerobes and facultative species such as coliforms or nongroup A streptococci;
or monomicrobial due to group A beta-haemolytic streptococci. Common
sites are the genitalia, groins and lower abdomen (Fig.
13.11a), although
necrotising fasciitis has been reported at almost any site. Patients are unwell,
febrile, with areas of subcutaneous induration and erythema; surgical emphysema
is palpable if gas-forming organisms are involved; necrotic patches of skin
develop. Treatment is by wide surgical excision of all affected soft tissues;
very large defects can be
Hydradenitis
suppurativa
Hydradenitis suppurativa (apocrinitis) is a chronic cicatrising
suppurative process caused by apocrine gland hyperplasia (Fig.
13.12). It is
common in the second and third decades of life and three times more common in
women than men. It occurs most commonly in the axilla, but can also affect the
groins and perineum. Locally, duct obstruction from keratin plugging occurs
leading to rupture of apocrine glands into the dermis and subdermal tissues with
subsequent superimposed infection. Pain can be severe. A course of metronidazole
has been found to be useful owing to the fact that Bacteroides is a
common causative organism; a prolonged course of erythromycin can be curative.
If the condition does not respond, then surgical excision is necessary. If a
wide area of skin needs to be removed, the wound needs to be covered by a
split-skin graft.
Lupus
vulgaris
Lupus vulgaris (tuberculosis of the skin) usually occurs between the
ages of 10 and 25, the face being the site of election. One or more
cutaneous nodules appear, with congestion of the surrounding skin (Fig.
13.13).
When blood is expressed with a glass slide, the brownish (apple-jelly) nodules
of individual tubercles can be seen. Extension occurs very slowly, but
ulceration is likely to follow sooner or later. The resulting ulcer tends to
heal in one situation as it extends to another. The mucous membranes of the
mouth and nose are sometimes attacked, either primarily or by extension from the
face. Oedema occurs if the fibrosis caused by the