أمراض الجلد

Skin Diseases

• Skin diseases are a broad category encompassing various conditions affecting the skin.

Natural Resistance of the Skin

• Dryness of the Skin: Limits bacterial growth due to the relative dryness of the skin's surface.
• Constant Cell Shedding: The skin's horny layer constantly sheds cells, assisting in removing potential pathogens.
• Sebaceous Secretions: Sebum, produced by sebaceous glands, contains natural antibacterial substances that prevent bacterial colonization.
• Low pH Environment: The skin's acidic environment (pH 5.5) discourages bacterial growth.
• Normal Skin Flora: The natural microbial community on the skin competes with potential pathogens through bacterial interference.

Common Bacterial Skin Infections and Causes

• Primary Bacterial Infections: Affect healthy skin, including impetigo, cellulitis, and erysipelas.

• Secondary Bacterial Infections: Occur in previously damaged skin (e.g., diabetic foot ulcers, pressure sores) and often involve multiple bacterial species. Common pathogens include Gram-positive bacteria (Staphylococcus aureus, Streptococcus pyogenes) and Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli).

• Staphylococcus aureus Infections: Include impetigo, cellulitis (occasionally), folliculitis, furunculosis, and carbuncles.

• Streptococcus pyogenes Infections: Include cellulitis, erysipelas, impetigo, bacterial intertrigo, and angular stomatitis.

Predisposing Factors for Infection

• High bacterial concentration
• Excess skin moisture
• Inadequate blood supply
• Nutrient availability for bacteria
• Damage to the corneal layer, facilitating bacterial entry

Primary Skin Infections

• Impetigo: A highly contagious bacterial skin infection primarily affecting children and frequently spreading through close contact. Causative agents include Staphylococcus aureus (including MRSA) and Streptococcus pyogenes.
• Erysipelas: An acute bacterial infection affecting the dermis layer of the skin. Primarily caused by Streptococcus pyogenes. Common sites of infection include the face and lower extremities, and typically affects one side of the body (unilateral).
• Cellulitis: An acute bacterial skin infection, affecting the epidermis and dermis. Often caused by Streptococcus pyogenes or Staphylococcus aureus (occasionally). Risk factors include injection drug use, minor trauma, abrasions, ulcers, recent surgery, poor nutrition, and compromised immunity.

Secondary Skin Infections

• Diabetic Foot Infections: Causative agents include Staphylococcus aureus, streptococci, Enterobacteriaceae, and Pseudomonas aeruginosa.
• Pressure Sores (Decubitus Ulcers): Causative agents include Staphylococcus aureus (including MRSA), streptococci, Enterobacteriaceae, and Pseudomonas aeruginosa.

Impetigo

• Definition: A common, contagious bacterial skin infection affecting the epidermis, predominantly in children, often spreading through close contact.
• Etiology: Causative organisms include Streptococcus pyogenes and Staphylococcus aureus (including MRSA).
• Common Sites: Most frequently seen on the face, but can occur anywhere on the body.
• Pathophysiology: Minor skin trauma allows bacteria to penetrate superficial skin layers, leading to infection. Warm, humid environments facilitate colonization and spread.
• Epidemiology: Most common in children and those in warm, humid climates. Spread is facilitated by close contact, poor hygiene, and crowded living conditions.
• Clinical Presentation: Non-bullous impetigo begins as small, fluid-filled vesicles that quickly become pus-filled, rupturing and releasing a purulent discharge that dries, creating yellowish or honey-colored crusts. Commonly itchy (pruritus). Bullous impetigo starts with larger, fluid-filled blisters (bullae) that eventually rupture, leaving behind thin brown crusts.
• Diagnosis: Primarily clinical, based on characteristic appearance. Laboratory tests typically unnecessary unless infection is recurrent or resistant.
• Treatment Goals: Eradicate infection promptly, relieve itching/discomfort, prevent spread, reduce complication risk (e.g., cellulitis or post-streptococcal glomerulonephritis), prevent recurrence.
• Treatment Options: Non-pharmacological therapy includes washing/soaking lesions with warm soapy water. Pharmacological therapy includes topical antibiotics (e.g., mupirocin) for mild cases and systemic antibiotics (e.g., dicloxacillin) for more severe or extensive cases, or CA-MRSA cases.

Erysipelas

• Definition: An acute bacterial infection affecting the dermis layer of the skin.
• Most Common Cause: Streptococcus pyogenes.
• Common Sites of Infection: Face, lower extremities.
• Typically Unilateral: (affects one side of the body).

Cellulitis

• Definition: An acute bacterial infection affecting the epidermis and dermis layers of the skin which can spread within the superficial fascia. Characterized by inflammation, with minimal or no necrosis of the tissue.
• Common Causes: Streptococcus pyogenes and Staphylococcus aureus (occasionally).
• Risk Factors: Injection drug use, minor trauma, abrasions, ulcers, recent surgery, poor nutrition, and compromised immunity.
• Pathogenesis: Bacteria often enter through breaks in the skin due to minor trauma, abrasions, ulcers, or surgery. The infection can spread through lymphatic tissue and potentially enter the bloodstream, making it a serious condition.
• Classification: Purulent cellulitis (involves purulent drainage without a simple abscess) and Non-Purulent cellulitis (lacks purulent drainage and no abscess).
• Clinical Presentation: Local symptoms include erythema (redness), edema (swelling), warmth over the affected area. Lesions are not elevated, and have poorly defined margins. Systemic symptoms include fever, chills, and malaise and potentially tender lymphadenopathy (swollen lymph nodes).
• Diagnosis: Primarily clinical (based on symptoms and physical examination). Laboratory tests such as CBC (complete blood count) may show leukocytosis (elevated white blood cell count) and CRP (C-reactive protein) elevated, indicating inflammation.
• Treatment: Non-pharmacological therapy includes elevating the affected area, sterile saline dressings (initially cool, followed by moist heat) to potentially concentrate the infection. Pharmacological therapy depends on the severity: Mild cases may use oral antimicrobials, severe cases often require intravenous (IV) antibiotics directed against likely pathogens or MRSA.

Folliculitis

• Definition: An infection of the hair follicles characterized by clustered, pruritic, and erythematous papules localized to the hair follicles.
• Clinical Presentation: Papules develop in areas subject to friction and perspiration. They may evolve into pustules that can spontaneously rupture within several days. Systemic signs are uncommon.
• Treatment: Non-pharmacological therapy may include warm moist compresses. Topical therapy (applied 2-4 times daily for 7 days) may include clindamycin topical, erythromycin topical, or mupirocin topical.

Furuncles

• Definition: Inflammatory nodules (boils/pustules) involving a hair follicle, occurring singularly or as multiple lesions.
• Clinical Presentation: Lesions begin firm, tender, and red. This develops into pustules, and often drain spontaneously. Systemic signs are rare.
• Treatment: For small furuncles, moist heat may aid in localization and drainage of pus. Larger furuncles/multiple furuncles may require incision (opening) and drainage. Moderate-to-severe infections (especially with systemic signs), will require antibiotics like Bactrim or doxycycline for 5-10 days if there is concern for CA-MRSA.

Carbuncles

• Definition: A collection of adjacent furuncles (boils) creating a larger, inflamed area.
• Clinical Presentation: Usually tender, swollen, and deep follicular masses, usually at the back of the neck, which is more common in those with diabetes mellitus.
• Treatment: Similar to furuncles, may require moist heat, incision & drainage, and antibiotics (like Bactrim or doxycycline) for 5-10 days, especially when there is a concern for CA-MRSA.

Diabetic Foot Infections

• Definition: Infections of the foot with several presentation types based on location: deep abscesses, cellulitis on the dorsum, and mal perforans ulcers (chronic, pressure-induced ulcers on the sole, common in patients with neuropathy).
• Etiology: Mild infections are typically caused by a single pathogen (monomicrobial). Severe infections involve multiple pathogens like Staphylococcus aureus, various streptococcal species, Enterococcus, Escherichia coli, Klebsiella, Pseudomonas aeruginosa, and Bacteroides fragilis.
• Classification: Mild: local infection, erythema ≤2 cm, no SIRS. Moderate: erythema >2 cm, deeper structures, no systemic symptoms. Severe: with 2+ features of Systemic Inflammatory Response Syndrome (SIRS) (requires hospitalization).
• Pathophysiology: Three main factors: neuropathy (sensory loss increases risk of injury), ischemia (poor lower limb blood flow impairs healing), and immunologic defects (reduced immune response in diabetes leads to higher infection risk).
• Clinical Presentation: Symptoms are variable, may include swelling or erythema of the foot, presence of pus, mild/normalised temperature. Lesions of varying sizes. Tenderness and foul-smelling odor (suggests anaerobic infection).
• Diagnosis: Primarily clinical. May include lab tests such as CBC to look for leukocytosis and culture and sensitivity tests to determine bacterial organisms causing infection.

Acne Vulgaris

• Definition: A chronic, long-lasting skin disorder involving hair follicles and sebaceous (oil) glands, primarily on the face, chest, and back.
• Causes: Hormonal changes, excessive sebum production, bacterial growth (Cutibacterium acnes), inflammation, genetic factors, diet/lifestyle, and cosmetic products.
• Types of Acne: Non-inflammatory acne includes open comedones (blackheads), closed comedones (whiteheads). Inflammatory acne includes papules, pustules, nodules, and cysts, leading to scarring.
• Classification Based on Severity: Mild acne (mainly comedones, and a few inflammations), moderate acne (widespread inflammations including papules/pustules), severe acne (large number of nodules/cysts and scarring).
• Epidemiology: High prevalence among adolescents, and up to 20% of adults. Slightly more common in males during adolescence, but prevalence is higher in females due to hormonal fluctuations. Psychosocial impacts are prominent, especially in adolescents, as acne may affect self-esteem.
• Treatment Goals: Reducing lesion count, preventing scarring, reducing inflammation and bacterial growth, and improving quality of life.
• Non-Pharmacological Therapy: Skin cleansing (gentle, non-comedogenic cleansers in mild cases) and dietary modifications may include avoiding high GI foods and dairy, sun protection (using non-comedogenic sunscreens), stress management to reduce triggers.
• Pharmacological Therapy: Retinoids (e.g., adapalene, tretinoin, tazarotene), topical benzoyl peroxide, topical antibiotics (e.g., clindamycin, erythromycin). More severe cases may need oral antibiotics (such as doxycycline or minocycline) plus topical therapies, hormonal therapy (e.g., spironolactone), and isotretinoin in the most resistant cases.

Intra-Abdominal Infections

• Definition: Infections contained within the peritoneum or retroperitoneal space, leading to hospital admission and serious outcomes such as death.
• Etiology: Intra-abdominal infections are usually polymicrobial, involving various aerobic bacteria (gram-positive cocci, gram-negative bacilli) and anaerobic bacteria.
• Types: Peritonitis (spontaneous bacterial peritonitis), biliary tract infections, appendicitis, diverticulitis, and infections following loss of bowel integrity due to trauma or surgery.
• Clinical Manifestations: Symptoms are variable and include abdominal pain and tenderness, rebound tenderness, fever, chills, nausea, and vomiting.

Cholecystitis

• Definition: Inflammation of the gallbladder often due to an obstructing stone.
• Management: Usually treated with surgical removal of the gallbladder (cholecystectomy).
• Infection: Some cases contain infections (50%), with microbes similar to those observed in primary peritonitis.

Cholangitis

• Definition: Infection of the common bile duct.
• Management: Typically treated with bile decompression, followed by antimicrobial therapy (covering common causative microbes such as PEK, anaerobes, Streptococci & Enterococci).

Peptic Ulcer Disease (PUD)

• Definition: A condition involving ulcers in the stomach (gastric ulcers) or duodenum (duodenal ulcers). Caused by the disruption of the mucosal barrier (which protects from gastric acid and pepsin).
• Etiology: Contributing factors include infection (H. pylori), NSAID use, stress, and excess gastric acid secretion (e.g., Zollinger-Ellison syndrome).
• Prevalence: Approximately 4.5 million cases annually in the US; about 10% lifetime prevalence in general population.
• Pathophysiology: Imbalance between the aggressive (acid and pepsin) factors and the defensive factors (mucus, bicarbonate, & prostaglandins).
• Diagnosis: Clinical evaluation (detailed history of symptoms and risk factors), endoscopic examination (gold standard), and testing for H. pylori. Lab tests (e.g., hemoglobin/hematocrit, serum gastrin) can assist in diagnosis and rule out other causes.
• Management: Lifestyle modifications (avoiding NSAIDs, alcohol, smoking, caffeine, and spicy foods), smaller, frequent meals, and stress reduction techniques are vital. Pharmacologic therapy includes PPI therapy, usually for 8 weeks, or eradication therapies if H. pylori infection is present. If NSAIDs cannot be avoided, a PPI might be needed.