Skin Diseases
In skin diseases, what matters are the location of the lesion, appearance and its evolution. One must be familiar with certain descriptive terms which are given below. It is advised that readers look at appropriate website for appearance of the lesion under particular category.
- Macule – Small lesion (5 mm or smaller) with colour change with flat surface.
- Papule – Similar to macule but with elevated surface (nodule is similar but greater in size).
- Vesicle – Papule filled with fluid. (Bulla is similar but greater in size)
- Pustule – Pus filled raised lesion.
- Wheal – Elevated, itching lesion with erythema and oedema. Remain for few minutes to hours.
- Scale – Dry, plate like desquamating skin in small patches.
- Lichenification – Thickened and rough skin.
- Excoriation – Breaking of epidermis in linear fashion.
Acute inflammatory lesions
- Urticaria – It is IgE antibody mediated hypersensitivity reaction induced by allergens like pollens, food items, drugs etc. It causes itching oedematous lesions called wheals. Urticaria may recur and enter into a chronic phase. Angioedema is similar but more severe and requires immediate treatment.
- Acute Eczematous Dermatitis – It is characterised by papulovesicular oozing lesions with itching. Later on, crust formation and scaling can occur. Depending on causative factor, it can be –
Contact dermatitis – it is due to contact with chemical or any substance to which a person is sensitive.
Atopic dermatitis – IgE mediated hypersensitivity reaction. It may alternate with Asthma.
Drug induced – Certain drugs may be responsible.
Chronic inflammatory Dermatosis
It represents a group of inflammatory skin disorders which remain for months or years.
Psoriasis
The cause of psoriasis is not known. Genetic and environmental factors may be responsible. Essentially, it induces secretion of cytokines and growth factors that induce Keratinocyte proliferation resulting into scales, typically of silver white colour. The lesions appear especially on extensor surfaces of elbow, knee so also scalp, lumbosacral area of the back and glans penis. The disease is sometimes associated with Arthritis.
Seborrheic Dermatitis
The disease affects principally the areas with dominant sebaceous glands such as scalp, forehead, behind the ear, nasolabial fold. It must be noted that it is not a disease of sebaceous glands. Its etiology is not known. Clinically the lesions are maculo– papular or erythematous yellowish base. Extensive scaling and crusting are present. Dandruff is also a common presentation.
Lichen Planus
It is believed to be of immunological origin. The skin lesion consists of itching papules which coalesce to form plaques. One can see whitish line or dots in between due to hyperkeratosis. These are specially noticed on extremities. Sometimes oral lesions are present on mucosa as white net like areas.
Inflammatory blistering disease
Pemphigus
Pemphigus is caused by autoantibodies that induce detachment of epidermis with mucosal epithelium. It occurs in both sexes mostly at later middle age. Although rare, it is a serious condition. It involves mostly inner aspect of thighs, flex or surfaces and occasionally oral lesions are present. Vesicular and bullous lesions are present which rupture producing shallow erosions.
Disorders of epidermal appendages
Acne Vulgaris
A most common disorder occurring at teenage is believed to be due to physiologic hormonal variation leading to alteration in hair follicle and sebaceous gland. It can be inflammatory or noninflammatory generally mixed type. Noninflammatory lesion consists of papules, which may contain a small blur keratin matter at centre. Inflammatory acne produces erythematous papules, nodules and pustules which may lead to scarring.
Infections of the skin
Impetigo
It is the common contagious superficial skin infection caused by streptococcus or staphylococcus aureus. It gives rise to pustules of varying size. Sometimes bullous form is seen.
Folliculitis
It can be superficial, which is very common. Any traumatic or chemical injury may predispose to it. Staphylococcus infection is most common giving rise to pustules.
Deep folliculitis can be a furuncle or carbuncle; generally originating at hair follicle. Carbuncle can be defined as a cluster of furuncles. Carbuncle generally occurs on the background of Diabetes or with low immunity.
Erysipelas and Cellulitis
Erysipelas is raised erythematous lesion caused mostly by streptococcus. Cellulitis affects deeper structures.
Warts (Verruca)
These are caused by papilloma virus. They occur in any part of the body. Appearance wise it may be flat, cauliflowerlike, black etc.
Molluscum Contagiosum
It is caused by poxvirus. The lesions are umbillicated i.e. papules with depression in the centre. Multiple lesions occur especially on trunk and anogenital area.
Herpes simplex
The infection occurs most commonly at mucocutaneous surfaces especially around mouth. The virus infects sensory and autonomic neurons and infections remains dormant. Later in life, symptoms recur on the skin with fever, psychological stress etc. Buccal mucous membrane and sometimes genital areas are affected. On the finger it can produce paronychia (whitlow).
Herpes zoster
Varicella zoster virus i.e. virus causing chickenpox, is the causative organism for this condition. After initial attack of chicken pox, the virus remains dormant in dorsal root ganglion of sensory nerves. Later on, especially in old age it may manifest as vesicles in the skin (dermatome) supplied by the nerve. Thoracic dermatomes are most frequently involved. Trigeminal nerve, especially ophthalmic division, if involved may lead to blindness. Generally, vesicles appear in the affected are, preceded or accompanied with mild to severe pain. Subsequently, the skin lesions are heated. However, pain continues.
Fungal infections
It goes under the head “Tinea” and depending on the part affected it can be tinea capitis (scalp), tinea corporis (body) etc. The fungus causes erythematous superficial annular (ring like) scaly lesions with minimal to severe itching. Tinea versicolor is the most common lesion affecting trunk.
Scabies
It is commonly seen in unhygienic conditions and spread with personal contact and even with clothes worn by the affected individual. It is caused by sarcoptes scabiei. Palms and soles especially the interdigital areas are affected with severe itching. Itching may lead to small vesicles and occasionally pustular lesions with superadded infection.
Head lice
Infestation with pediculus humanus affects scalp causing itching, secondary infection sometimes with cervical lymphadenopathy.
Other common disorders of skin
Alopecia areata / totalis
Alopecia areata is patchy hair loss while totalis represents hair loss of the whole scalp. The cause is not known.
Venous disease and skin
Venous stasis especially in lower extremities due to various veins, may lead to itchy lesions, sometimes ulceration occurs which is difficult to heal.