Page 620 - Concise Pathology for Exam Preparation ( PDFDrive )

22 The Skin 605

Q. Write briefly on superficial mycosis.

Ans. The superficial mycosis causing fungi (dermatophytes) make up a group of fungi that
is confined to the outermost layers of the skin or its appendages.
• Tinea capitis is most common in children, in whom it presents with circular or
ring-shaped patches (thus also called ‘ringworm’) of alopecia (hair loss) with ery-
thema and scaling and is usually caused by Trichophyton tonsurans.
• T. rubrum and T. mentagrophytes are responsible for many other types of Tinea infections
(eg, Tinea cruris, pedis and corporis).
• Tinea versicolor is caused by Malassezia furfur (a yeast) and is associated with areas of
hyper- and hypopigmentation. Scrapings reveal the classic ‘spaghetti (hyphae) and
meatball (yeast)’ appearance.
• Candida albicans commonly produces disease involving the skin (common cause of diaper
rash) and nails (onychomycosis).

Q. Enumerate and describe chronic inflammatory dermatoses.

Ans. Chronic inflammatory dermatoses include
1. Psoriasis
• This is a chronic inflammatory dermatosis associated with arthritis, myopathy, enter-
opathy and heart disease
• It affects skin of the elbows, knees, scalp and lumbosacral areas.
• The most typical lesion is a well-demarcated, itchy, pink to salmon plaque covered by
loosely adherent silvery white scales.
• Nail changes are seen in up to 30% cases and include pitting, thickening, yellow-
brown discoloration, crumbling and separation of the nail plate from the underlying
bed (onycholysis).
• Many of these patients present with psoriatic arthritis, which may manifest as classic
distal interphalangeal joint involvement, symmetric polyarthritis, asymmetric oligoarthri-
tis (the most common type of psoriatic arthritis) or as ankylosing spondylitis.
• Pathogenesis of psoriasis is multifactorial in origin with the contribution from the fol-
lowing:
• Immunologic status of the individual
• Genetic susceptibility (strong association with HLA-C especially with HLA-Cw*0602
allele)
• Environmental factors
1
1
• There is accumulation of CD4 T H 1 and CD8 T cells in the epidermis, which se-
crete cytokines and growth factors inducing keratinocyte hyperproliferation resulting
in the characteristic lesions. It can be induced in susceptible individuals by local
trauma (Koebner phenomenon).
Morphology:
• Marked epidermal thickening (acanthosis)
• Regular downward elongation of rete ridges (psoriasiform hyperplasia)
• Rapid epidermal cell turnover results in loss of stratum granulosum with extensive
parakeratotic scaling
• Suprapapillary thinning (thinning of the epidermal cell layer overlying the tips of
dermal papillae)
• Vessels bleed on removal of the scale, giving rise to multiple bleeding points (Auspitz’s sign)
• Neutrophils form small aggregates within the spongiotic superficial epidermis (pus-
tules of Kogoj) and the parakeratotic stratum corneum (Munro microabscesses)
2. Lichen planus
• Lichen planus is characterized by pruritic, purple, polygonal, papules and plaques
in the skin and mucosa.
• It is self-limited and may resolve spontaneously; oral lesions may persist for years.
• The papules are highlighted by white dots or lines called Wickham’s striae.
• Pathogenesis is unknown, however, it is hypothesized that it occurs due to cytotoxic
T cell response to an altered antigen in the basal cells.
Morphology:
• Basal keratinocytes show degeneration and necrosis.

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