Page 786 - Textbook of Pathology, 6th Edition

770 Sex-linked ichthyosis is a sex-(X) linked recessive prone to develop infections, especially of lungs, and
disorder. It begins shortly after birth and affects extensor as lymphoma-leukaemia.
well as flexor surfaces but palms and hands are spared.
Histologically, the papillary dermis shows numerous
Histologically, there is hyperkeratosis with normal or dilated blood vessels.
thickened granular cell layer and acanthosis.
II. NON-INFECTIOUS INFLAMMATORY DERMATOSES
2. KERATOSIS PALMARIS ET PLANTARIS. The
condition occurs as both autosomal dominant and autosomal A very large number of skin diseases have acute or chronic
recessive forms. It mainly affects the palms and soles as inflammation as a prominent feature. A few selected
localised or diffuse lesions. examples of non-infectious acute and chronic inflammatory
dermatoses which have not been covered in other groups of
Histologically, there is marked hyperkeratosis, hyper- dermatoses are given below.
granulosis, acanthosis and mild inflammatory infiltrate 1. DERMATITIS (ECZEMA). The pathologic term derma-
in the upper dermis. titis is synonymous with the clinical term eczema. Both refer
to inflammatory response to a variety of agents acting on
3. XERODERMA PIGMENTOSUM. This is an autosomal the skin from outside or from within the body such as
recessive disorder in which sun-exposed skin is more chemicals and drugs, hypersensitivity to various antigens
vulnerable to damage. The condition results from decreased and haptens etc. Accordingly, clinical types such as contact
ability to repair the sunlight-induced damage to DNA. dermatitis, atopic dermatitis, drug-induced dermatitis,
Patients of xeroderma pigmentosum are more prone to photo-eczematous dermatitis and primary irritant dermatitis
develop various skin cancers like squamous cell carcinoma, are described. Many idiopathic varieties of skin disorders
basal cell carcinoma and melanocarcinoma. such as pompholyx, seborrheic dermatitis, exfoliative
dermatitis (erythroderma) and neurodermatitis (lichen
Histologically, the changes include hyperkeratosis, simplex chronica) are also included under this heading. In
thinning and atrophy of stratum malpighii, chronic general, these conditions are clinically characterised by
inflammatory cell infiltrate in the dermis and irregular itching, erythema with oedema, oozing and scaling.
accumulation of melanin in the basal cell layer. Changes However, irrespective of the clinical type of dermatitis, the
of skin cancers mentioned above may be present in histopathologic picture is similar.
advanced stage.
SECTION III
Histologically, dermatitis reaction may be acute, subacute
4. DARIER’S DISEASE (KERATOSIS FOLLICULARIS). or chronic:
The condition is either transmitted as autosomal dominant Acute dermatitis is characterised by considerable
disorder or as a mutation. In typical cases, there is extensive spongiosis (intercellular oedema) that may lead to forma-
papular eruption. tion of intraepidermal vesicles or bullae. The vesicles and
bullae as well as the oedematous epidermis are permeated
Histologically, the characteristic changes are hyper- by acute inflammatory cells. The upper dermis shows
keratosis, papillomatosis and dyskeratosis. Dyskeratosis congested blood vessels and mononuclear inflammatory
results in the formation of ‘corps ronds’ (present in the cell infiltrate, especially around the small blood vessels.
granular layer as a central homogeneous basophilic Subacute dermatitis may follow acute dermatitis.
dyskeratotic mass surrounded by a clear halo) and ‘grains’ Spongiosis and vesicles are smaller than in acute
Systemic Pathology
(having grain-shaped elongated nuclei surrounded by dermatitis. The epidermis shows moderate acanthosis and
homogeneous dyskeratotic material) and there is varying degree of parakeratosis in the horny layer with
appearance of suprabasal clefts containing acantholytic formation of surface crusts containing degenerated
cells. The dermis often shows chronic inflammatory cell leucocytes, bacteria and fibrin. The dermis contains
infiltrate. perivascular mononuclear infiltrate. The classical example
of subacute dermatitis is nummular dermatitis.
5. URTICARIA PIGMENTOSA. Urticaria pigmentosa may Chronic dermatitis shows hyperkeratosis, parakera-
occur as congenital form or may appear without any family tosis and acanthosis with elongation of the rete ridges and
history in the adolescents. Clinically, the condition presents broadened dermal papillae. Vesicles are absent but slight
as extensive pigmented macules. spongiosis may be present. The upper dermis shows
perivascular chronic inflammatory infiltrate and fibrosis
Histologically, the epidermis is normal except for an (Fig. 26.3). The most characteristic example of chronic
increase in melanin pigmentation in the basal cell layer. dermatitis is lichen simplex chronicus.
The characteristic feature is the presence of numerous
mast cells in the dermis. 2. URTICARIA. Urticaria or hives is the presence of
transient, recurrent, pruritic wheals (i.e. raised erythematous
6. ATAXIA TELANGIECTASIA. An autosomal recessive areas of oedema). Hereditary angioneurotic oedema is an
disorder, ataxia appears in infancy, while telangiectasia uncommon variant of urticaria in which there is recurrent
appears in childhood. The lesions are located on the oedema not only on the skin but also on the oral, laryngeal
conjunctivae, cheeks, ears and neck. These children are more and gastrointestinal mucosa (page 97).