Though rashes vary in appearance, similar rashes are seen in many diseases. Thorough understanding of morphology and perspicacious indicators help in arriving at a primary cause. In this article, Dr. YK Amdekar lists these indicators and other essential practice points that can help doctors approach and manage skin rashes and disease.

To read other originals by Dr. YK Amdekar, click here.

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Skin rash may appear red, swollen, itchy, or irritated and also may present as a change in texture (for e.g., rough – sandpaper rash in scarlet fever). Rashes are not pathognomonic of any disease as similar rashes are seen in many diseases. We need to look at morphology (macular, popular, vesicular, nodular, pustular, purpuric, confluent), progression (spread, peeling – dying skin, pigmentation), areas involved (hands and feet, trunk and back, face - rashes that spare hands and feet are scarlet fever and impetigo), blanching (becoming white or pale after pressure as in inflammatory rash), time of appearance of the rash (they usually appear in the first few days, but if it appears after a week, it is mostly an inflammatory disease), accompanying symptoms and signs, history of allergy and drugs, and family history of similar disease.

Common causes related to morphology

• Centrally distributed maculopapular rash- Viral infections, rickettsia, inflammatory diseases, drugs
• Confluent blanching erythema- Kawasaki, scarlet fever, toxin-induced rash
• Vesicular rash- Varicella, herpes simplex, enteroviral infection, skin-scalded syndrome, Steven-Johnson syndrome
• Urticarial rash- Coxasackie, HBV, HCV, vasculitis, malignancy, drug, allergy
• Purpuric rash- HUS, DIC, ITP, leukaemia, meningococcemia, vasculitis, haemorrhagic viral fever
• Nodular- TB, fungal, rickettsial, erythema nodosum
• Circular scaly rash with a raised border
• Skin in the middle of the lesion appears normal; red, itchy with prominent borders- ringworm
• Scaly, blisters that may ooze and form crusts- Contact dermatitis, allergic eczema
• Red blisters which are itchy- Hand, foot, and mouth disease
• Red, wet, and irritating- Diaper rash
• Silvery scaly with sharply defined borders which may be itchy, often on the scalp, elbows, knees, and back- Psoriasis
• Vesicular- Chickenpox, herpes simplex, Stenven-Johsnon syndrome, skin scalded syndrome
• Butterfly rash on face sparing nasolabial fold- Systemic lupus erythematosus
• Painful swollen red rash with fever- Cellulitis
• Pimples or blisters, extremely itchy, scaly, raised white lines- Scabies
• White or yellow scaly patches that flake off
• Areas are red, greasy, or oily- Seborrhoea
• Red skin all over sparing hands and feet, sandpaper rash- Scarlet fever

Clinical approach to skin rash

Does it represent underlying serious disease?

In every disease, physicians must rule out serious disease even before embarking on finding the cause.

1. Purpuric rash suggests severe and often life-threatening diseases such as meningococcemia, disseminated intravascular coagulation abnormality as in sepsis, or haemolytic uremic syndrome with renal involvement, vasculitis of different aetiologies including malignancy, leukaemia, and bone marrow aplasia.
2. Gangrenous rash is typical of rickettsial infection.
3. Vesiculo-bullous rash in a sick-looking child denotes probable drug reaction as in Steven-Johnson syndrome. These conditions merit hospitalisation and prompt management.

Does it represent a potentially evolving serious disease?

Skin rash with inflammation of mucus membranes, fever and/or multisystem involvement indicate diseases that may worsen over time as in the case of Kawasaki disease (may develop coronary artery dilation leading to myocardial infarction) and toxic reactions to staphylococcal or streptococcal infections (prolonged fever with the risk of a fatality). Such suspected diseases ideally need a referral for expert opinion for investigations and management.

Once seriousness is ruled out, is it primary skin disease or systemic disorder?

Such diseases are usually benign though they need a correct diagnosis to prevent chronicity (scabies, eczema, contact dermatitis- need referral to a dermatologist) and close monitoring to rule out complications if any (infectious disease such as measles, varicella, mumps).

Rash itches or itchy rashes?

It is important to assess what started first – was it the rash or the itch? Unless asked for, such a history does not come forth and even then most patients or parents of children might not have noticed as itch and rash follow in quick succession.

Itch at the onset without a rash may suggest autonomic nervous system abnormality (worsened by anxiety or stress), diabetes, or an increase in bile salts as in obstructive jaundice. Such primary conditions causing itching are often missed. Rarely, Hodgkin's lymphoma or other immune disorders may present with itching before other symptoms and signs manifest.

Management

1. Life-threatening and potentially serious conditions are managed by experts. It is ideal that dermatologists manage primary chronic skin diseases.
2. Infections may be self-limiting or may need antibiotics as in the case of scarlet fever or skin infection such as scabies, cellulitis, or impetigo.
3. Many other conditions are managed with palliative measures more than curative treatment.
4. Oral antihistamines are necessary for severe allergic or itching disorders. Local application of steroids, antibiotics, antiseptics, moisturizers, and soothing agents may be required. Ointments contain 80% oil and 20% water, whereas creams contain 50% of each oil and water. So ointments are preferred for dry skin as they provide moisture and also possess antiseptic properties. Lotions are dilute forms of cream.
5. Home remedies like cold compress help temporarily to offer relief from severe itching. Oatmeal bath is recommended as it works as an anti-inflammatory and antioxidant. Aloe vera has medicinal properties and is present in many skin creams. Coconut oil is a moisturiser and also has antibacterial activity.

In summary, physicians must rule out life-threatening and potentially serious conditions, and then try to be rational in approach to conditions presenting as a skin rash. Timely referral is important for better outcome.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.