Page 787 - Textbook of Pathology, 6th Edition

Erythema nodosum, acute or chronic, is the most 771
common form. The lesions consist of tender red nodules, 1-5
cm in diameter, seen more often on the anterior surface of
the lower legs. Erythema nodosum is often found in
association with bacterial or fungal infections, drug intake,
inflammatory bowel disease and certain malignancies.
Erythema induratum is a less common variety. The
lesions are chronic, painless, slightly tender, recurrent and
found on the calves of lower legs.
Histologically, the early lesions show necrotising vascu-
litis involving the blood vessels in the deep dermis and
subcutis. In chronic stage, there is inflammatory infiltrate
consisting of lymphocytes, histiocytes and multinucleate
giant cells. The infiltrate is located in the septa separating
the lobules of fat.

5. ACNE VULGARIS. Acne vulgaris is a very common
chronic inflammatory dermatosis found predominantly in
adolescents in both sexes. The lesions are seen more
commonly on the face, upper chest and upper back. The
appearance of lesions around puberty is related to
Figure 26.3 Chronic dermatitis (eczema). The epidermis shows physiologic hormonal variations. The condition affects the
hyperkeratosis, acathosis and broadened papillae and spongiosis of the hair follicle, the opening of which is blocked by keratin
epidermal layers. The dermis shows mild perivascular chronic material resulting in formation of comedones. Comedones may
inflammatory cell infiltrate.
be open having central black appearance due to oxidation of
melanin called black heads, or they may be in closed follicles CHAPTER 26
Histologically, there is dermal oedema and a perivascular referred to as white heads. A closed comedone may get infected
mononuclear infiltrate. There is localised mast cell and result in pustular acne.
degranulation by sensitisation with specific IgE antibodies
but no increase in dermal mast cells (c.f. mastocytosis in Histologically, a comedone consists of keratinised cells,
which there is increase in dermal mast cells). sebum and bacteria. The hair follicle containing a
comedone is surrounded by lymphocytic infiltrate in
3. MILIARIA. Miliaria is a condition in which there is papular acne, and neutrophilic infiltrate in pustular acne. The Skin
cutaneous retention of sweat due to obstruction of sweat Sometimes, the wall of the distended follicle is disrupted
ducts. There are 2 types of miliaria: miliaria crystallina and so that the contents escape into the dermis where they
miliaria rubra. may incite granulomatous reaction.
Miliaria crystallina occurs when there is obstruction of
sweat duct within the stratum corneum. It occurs in areas of III. INFECTIOUS DERMATOSES
the skin exposed to sun or may occur during a febrile illness. Microorganisms such as bacteria, viruses and fungi are
Histologically, there are intracorneal or subcorneal responsible for a large number of dermatoses. Some common
vesicles which are in continuity with underlying sweat examples of each category are described below.
ducts. 1. IMPETIGO. Impetigo is a common superficial bacterial
infection caused by staphylococci and streptococci. The
Miliaria rubra occurs when there is obstruction of sweat condition may occur in children or in adults and more
ducts within the deeper layers of the epidermis. It is seen commonly involves hands and face. The lesions appear as
more often in areas of skin covered by clothes following vesico-pustules which may rupture and are followed by
profuse sweating and the lesions are itchy. characteristic yellowish crusts.

Histologically, there are spongiotic vesicles in the stratum Histologically, the characteristic feature is the subcorneal
malpighii similar to those seen in dermatitis. These pustule which is a collection of neutrophils under the
vesicles are in continuity with a sweat duct. Adjacent stratum corneum. Often, a few acantholytic cells and
dermis usually shows chronic inflammatory infiltrate. gram-positive bacteria are found within the pustule. The
upper dermis contains severe inflammatory reaction
4. PANNICULITIS (ERYTHEMA NODOSUM AND composed of neutrophils and lymphoid cells.
ERYTHEMA INDURATUM). Panniculitis is inflammation
of the subcutaneous fat. Panniculitis may be acute or chronic. 2. VERRUCAE (WARTS). Verrucae or warts are common
Generally, panniculitis appears as nodular lesions, viral lesions of the skin. They are caused by human
predominantly on the lower legs. The following types of papillomaviruses (HPV) that belong to papovavirus group,
panniculitis are described: a type of DNA oncogenic virus (page 224). More than