Common Skin Conditions and Their Causes

Erythema Nodosum: A subcutaneous inflammation, erythema nodosum is often associated with inflammatory bowel disease, tuberculosis, sarcoidosis, or a recent streptococcal infection. It is characterized by raised nodules on the lower extremities.

Morbilliform Rash: A mild hypersensitivity skin reaction, the morbilliform rash is a maculopapular eruption that blanches with pressure. It is caused by drugs such as penicillin, sulfonylurea, thiazide, allopurinol, and phenytoin.

Erythema Multiforme: A target-like lesion that commonly appears on the palms and soles, erythema multiforme is usually caused by drugs such as penicillins, phenytoin, NSAIDs, or sulfa drugs. It can also be caused by Mycoplasma or herpes simplex.

Tinea Corporis: A fungal infection, tinea corporis is characterized by ring-shaped, scaly patches with central clearing and a distinct border.

Urticaria: A hypersensitivity reaction that results in wheals and hives, urticaria is most often associated with drug-induced mast cell activation. Aspirin, NSAIDs, and phenytoin are common culprits.

Understanding Common Skin Conditions and Their Causes

Differentiating Skin Conditions Based on Location and Distribution

When it comes to diagnosing skin conditions, the location and distribution of the rash or lesion are just as important as its appearance. For example, a rash in the flexural regions of an adult patient, such as the popliteal region, is likely to be atopic dermatitis. This is especially true if the patient has a history of asthma, indicating an atopic tendency. Acute dermatitis typically presents with redness, swelling, vesicles, and papules.

Other skin conditions have different characteristic distributions. Dermatitis herpetiformis, which is associated with coeliac disease and malabsorption, typically appears as grouped vesicles or papules on the elbows, knees, upper back, and buttocks. Seborrhoeic dermatitis is found in areas with sebaceous glands, such as the scalp, eyebrows, and presternal regions. Lichen planus presents as flat-topped, pruritic, polygonal, red-to-violaceous papules or plaques, usually on the wrists, ankles, or genitalia. Psoriasis, on the other hand, produces silvery, scaling, erythematosus plaques, primarily on the extensor surfaces.

In summary, understanding the location and distribution of a skin condition can help clinicians make an accurate diagnosis and provide appropriate treatment.

Cutaneous Larva Migrans and Other Skin Conditions: A Differential Diagnosis

Cutaneous larva migrans is a common skin condition caused by the migration of nematode larvae through the skin. It is typically found in warm sandy soils and can be diagnosed based on the history and appearance of serpiginous lesions. Treatment involves the use of thiobendazole. Other skin conditions, such as impetigo, tinea pedis, and photoallergic dermatitis, have different causes and presentations and are less likely to be the correct diagnosis. Larva currens, caused by Strongyloides stercoralis, is another condition that can cause itching and skin eruptions, but it is typically associated with an intestinal infection and recurrent episodes. A differential diagnosis is important to ensure proper treatment and management of these skin conditions.

Skin Conditions and Pigmentation Changes

Pigmentation changes in the skin can be caused by various factors, including skin conditions and hormonal imbalances. Here are some examples:

Pityriasis versicolor: This common skin complaint is characterized by flaky, discoloured, hypopigmented patches that mainly appear on the chest and back. It is caused by the overgrowth of a yeast called Malassezia furfur.

Whipple’s disease: This rare bacterial infection can cause hyperpigmentation in some cases.

High oestriol: Elevated levels of this hormone, which can occur during pregnancy, are associated with hyperpigmentation.

Neurofibromatosis type I: This genetic disorder causes numerous café-au-lait patches, which are hyperpigmented patches.

Urticaria pigmentosa: This condition, which typically develops in childhood, causes hyperpigmented patches that usually fade by the teenage years.

Understanding Scabies: Symptoms and Characteristics

Scabies is a skin condition caused by the infestation of the mite Sarcoptes scabiei, variety hominis. The female mite burrows into the skin, creating characteristic lesions known as burrows. However, the absence of burrows does not rule out a diagnosis of scabies. Other symptoms include erythema, or redness and scaling of the skin, and excoriations, or skin abrasions caused by scratching. In severe cases, crusting patches may develop, particularly in crusted scabies, a highly contagious variant of the condition. Prurigo nodules, or small bumps on the skin, may also occur in scabies, especially in young children. It is important to seek medical attention if you suspect you have scabies, as prompt treatment can prevent the spread of the condition.

The patient is presenting with erythema nodosum, which may have an unknown cause or could be related to their extensive travel history. While a skin biopsy may provide a definitive diagnosis, the best initial investigation is a chest X-ray to rule out tuberculosis and sarcoidosis. A blood film is not necessary as there is no indication of malaria. An ultrasound of the abdomen is not useful in this case, as the skin lesions are the primary concern. Stool microbiology is not necessary as there is no mention of diarrhea. While a skin biopsy may provide information on the lesions themselves, it does not aid in identifying the underlying cause.

Management of Hirsutism in Polycystic Ovary Syndrome: First-Line Options

Polycystic ovary syndrome (PCOS) is a condition characterized by irregular menstrual cycles, excess hair growth, and raised hormone levels. In patients with PCOS experiencing hirsutism and irregular periods, the first-line management option is the oral combined contraceptive pill. This medication reduces hyperandrogenism by suppressing ovarian androgen secretion and increasing binding of androgens, thereby reducing excess hair growth. Metformin can also be used to improve insulin resistance and aid weight management, but it would not be the first-line choice for managing hirsutism. Eflornithine can be used for hirsutism, but in this patient, starting the contraceptive pill will not only treat her hirsutism but also allow for regular withdrawal bleeds and regulate her menstrual cycle. The progesterone-only pill and topical minoxidil are not recommended as first-line options for managing hirsutism in PCOS patients.

Common Skin Conditions: Asteatotic Eczema, Contact Dermatitis, Lichen Planus, Scabies, and Venous Ulceration

Asteatotic eczema is a skin condition that commonly affects elderly individuals due to over-washing and dry winter climate. It can also be associated with diuretic use and hypothyroidism. The condition causes dry, itchy skin with a unique crazy paving pattern on the limbs. Treatment involves using emollients and mild topical steroids.

Contact dermatitis, on the other hand, is caused by friction and environmental factors such as cold or exposure to chemicals like detergents and solvents. It typically affects the hands and does not display the crazy paving pattern seen in asteatotic eczema.

Lichen planus is characterized by a pruritic, papular eruption with a violaceous color and polygonal shape. It presents with a lace-like pattern, unlike the crazy paving pattern seen in asteatotic eczema.

Scabies is an itchy rash caused by mites that burrow under the skin’s surface. It often affects the very young and elderly, particularly those who live in crowded areas or institutional care. It presents with burrows, particularly on the web spaces between fingers, followed by a hypersensitivity rash. Treatment involves using topical insecticides like 5% permethrin.

Finally, venous ulceration is present on the lower limbs and can be itchy if associated with venous eczema. However, the legs often display a brown pigmentation of haemosiderin, and a venous ulcer would not present as described in this question.

In summary, understanding the characteristics of these common skin conditions can help with accurate diagnosis and appropriate treatment.

Treatment Options for Chronic Plaque Psoriasis

Chronic plaque psoriasis can be a challenging condition to manage, especially when topical therapies are not effective. In such cases, systemic therapies may be considered. Methotrexate and ciclosporin are two such options that can be effective in inducing remission. However, it is important to weigh the potential side-effects of these medications before starting treatment. Vitamin D analogues and coal tar products may not be effective in severe cases of psoriasis. Oral steroids are also not recommended as a long-term solution. Biological therapy, such as etanercept, should only be considered when standard systemic therapies have failed. It is important to follow NICE guidelines and trial other treatments before considering biological agents.

Next Steps in Psoriasis Treatment: Narrow-Band UVB Phototherapy

When topical treatments fail to improve psoriasis symptoms, the next step in treatment is often narrow-band ultraviolet B (UVB) phototherapy. While it has a reasonable success rate, it also comes with potential complications such as an increased risk of skin cancer. Patients with a history of skin cancer may not be recommended for this treatment.

Changing topical steroids would not be an appropriate step in the management plan. Instead, it is necessary to move onto the next step of the psoriasis treatment ladder. Biologics are not indicated at this stage and should only be considered as an end-stage treatment due to their high cost and significant side effects.

Psoralen with local ultraviolet A (UVA) irradiation may be appropriate for patients with palmoplantar pustulosis. However, for most patients, stopping steroids is not recommended. Instead, narrow-band UVB phototherapy should be commenced without stopping steroids to optimize treatment and increase the chances of success.