Dermatopathology
INTRODUCTION
Normal Skin Histology
Epidermis
- Keratinocytes make up most of each layer of the epidermis
1) Cornified Layer - stratum corneum
Ø anucleated
2) Granular Layer – stratum granulosum
Ø flattened cells with tiny basophilic keratohyaline granules
Ø 1-2 cell layers thick
3) Spinous Layer – stratum spinosum
Ø usu the largest region
4) Basal Layer – stratum basalis
Ø REGENERATIVE LAYER
Ø May have mitoses
Ø Cells may be more basophilic than the spinous layer cells
- Non-keratinocytic cells
¨ Melanocytes
- in basal layer and hair follicle
- produce the melanin pigment and TRANSFER it to the keratinocytes
- SKIN PIGMENTATION is directly correlated with the amount of melanin contained in the KERATINOCYTES not the melanocytes!!!!
¨ Langerhan’s cells
¨ Merkel cells
Dermis
- composed of CT and elastic fibers
Ø Two components
1) Papillary Dermis – superficial
2) Reticular dermis – deep
- also contains the vessels, nerves, muscle, nerve end organs, skin adnexae
- Pilosebaceous unit – hair follicle and sebaceous gland
- Sweat glands – excretory duct and a coiled secretory portion.
Subcutis
- the fat deep to the dermis
Infectious diseases and infestations:
Molluscum contagiosum
- caused by molluscum contagiosum virus – poxvirus group
- umbilicated papules, usually < 5mm in diameter
- mostly occurs in kids
- AIDS patients may have widespread lesions
- HISTO
Ø intracytoplasmic inclusions called molluscum bodies are present in the keratinocytes
Ø inclusions get larger as the cells mature towards the surface
Verruca = wart
- caused by HPV – papovavirus
- Verruca vulgaris – common wart
- Usually occurs on dorsal fingers and hands
- Circumscribed, flesh colored papule(s) with irregular surface and black dots
- HISTO
Ø acanthotic epidermis with hyperkeratosis
Ø hypergranulosis and papillomatosis
Ø dilated capillaries in the dermal papillae = black dots clinically
Ø koilocytes are virally-infected cells in the epidermis with a dark, wrinkled nucleus surrounded by a clear halo.
- Others
Ø Verruca plana – face, flat
Ø Condyloma acuminatum
Ø Deep palmarplantar wart
AIDS Associated Skin Disorders
- Common Infections
Ø Bacterial: impetigo, folliculitis, bacillary angiomatosis, mycobacteria
Ø Fungal: candida, dermatophytes, cryptococcus, histoplasma
Ø Viral: HSV, HPV, CMV, EBV, molluscum contagiosum
- Dermatitis
- seborrheir dermatitis, xerotic (asteotic) dermatitis, cutaneous drug eruptions
- Hair and nail disorders
- loss of scalp hair
- eyelash elongation
- Kaposi’s sarcoma
Arthropod infestations
1) Scabes
-
caused by the mite (Sarcoptes scabiei) which burrows into the stratum corneum - you get it from close contact
- causes pruitic papules & vesicles at the ends of small streaks
- on hands, wrists, breasts, male genitals
- HISTO
Ø inflammation + spongiosus in the epidermis
Ø eosinophils usu present (remember NAACP)
Ø if biopsy: may see mites or eggs in the stratum corneum
2) Pediculosis
-
caused by the louse; different ones cause it in different circumstances
1) Head louse – Pediculus humanus capitis – kids
2) Pubic Louse – Phthirus pubis – sexual contact
3) Body louse – Pediculus humanus corporis – “vagabond’s disease”
- Causes itching, scalp impetigo (2o to scratching), cervical lymphadenopathy may occur with head lice, nits (eggs) of head lice are attached to the hair.
Common dermatologic conditions in the Hospitalized Patient
Leukocytoclastic vasculitis
- also called small vessel neutrophilic vasculitis, hypersensitivity vasculitis
- Etiology: injury to small vessels in the dermis
Ø Infection: bacteria, viruses, fungi
Ø Immunologic injury
q Immune complex mediated
§ Henoch-Schonlein Purpura – palpable purpura, abdominal pain, and hematuria
§ Cryoglobulinemia
§ Serum Sickness
§ Connective tissue disorders (Lupus, RA)
q Drugs and Chemicals
q Cancer
q Wegener’s granulomatosis – ANCA+
- Clinical – palpable purpura
Ø Purpura can be caused by inflammatory or non-inflammatory conditions
1) Inflammatory
- vasculitis
2) Non-inflammatory
- deficient collagen formation
- idiopathic thrombocytopenic purpura (ITP)
- thrombotic thrombocytopenic purpura (TTP)
- coumadin necrosis
- Histo
Ø 3 essential elements
1) Fibrinoid degeneration
2) Neutrophilic infiltrate
3) Hemorrhage
Cholesterol Embolism
- caused by some stherosclerotic plaque that dislodges from a vessel wall and gets “stuck” in the distal arterioles
- Clinical presentation
Ø older patients with severe atherosclerotic disease
Ø can cause livedo reticularis, blue digits, gangrene of extremity
Ø distal pulses are present- therefore it is arteriolar not arterial
- HISTO
Ø needle-shaped spaces (“cholesterol clefts”) with associated inflammation & fibrosis within the small vessels
- Diagnosis – deep skin biopsy (get the SQ space); remember the emboli are focal, so you may not get
Cutaneous Drug Reactions
- wide spectrum
- Erythema multiforme, leukocytoclastic vasculitis, fixed drug eruption, Exanthemic drug eruption
Acute Cutaneous Graft vs. Host Disease
-
Caused by the donor T-lymphocytes reacting against the histocompatibility antigen on cells of the immunodeficient recipient - Clinical: bone marrow transplant recipients, skin eruption + liver disruption + diarrhea; If severe may resemble erythema multiforme/TEN
-
4 grades – (I to IV)
Tags: bacillary angiomatosis, Bacterial: impetigo, cryptococcus, dermatophytes, epidermis, folliculitis, Fungal: candida, histoplasma, hypergranulosis, Langerhans cells, melanocytes, Merkel cells, mycobacteria, Papillary Dermis, papillomatosis, stratum basalis, stratum corneum, stratum granulosum, stratum spinosum
