Skin complaints arrive constantly in primary care, and most of the skill is pattern recognition plus knowing which rash is not benign. These questions cover eczema, psoriasis and acne management, recognising cellulitis and its red flags, topical steroid potency, and the presentations that warrant urgent referral rather than a prescription.
Question 1
A 17-year-old female, 5 years post-menarche, reports cycles every 60 to 90 days. Physical examination reveals a BMI of 32 but no evidence of hirsutism or severe acne. Which finding is required to establish the diagnosis?
- A) Documenting an elevated serum free testosterone laboratory level.✓
- B) Identifying polycystic morphology on a transvaginal pelvic ultrasound.
- C) Demonstrating an elevated luteinizing hormone to gonadotropin ratio.
- D) Confirming severe insulin resistance via fasting glucose testing.
💡 Key Takeaway
Adolescent PCOS diagnosis requires both ovulatory dysfunction and evidence of hyperandrogenism, which can be clinical or biochemical.
Show rationale
In adolescents, diagnosing PCOS requires both ovulatory dysfunction (which this patient has, given her oligomenorrhea 5 years post-menarche) and hyperandrogenism. Because she lacks clinical signs like hirsutism or severe acne, you must demonstrate biochemical hyperandrogenism via elevated serum free or total testosterone, making Option A correct. Option B is incorrect; ultrasound is not recommended for diagnosis within eight years of menarche due to normal physiologic variations in ovarian morphology. Option C is incorrect; an elevated LH-to-FSH ratio is frequently seen in PCOS but is not a recognized diagnostic criterion. Option D is incorrect; while patients with PCOS and obesity often have insulin resistance, metabolic testing is used for risk stratification and management, not to establish the primary diagnosis.
Question 2
An unvaccinated 4-year-old child presents with a three-day history of high fever, cough, and coryza. Today, the mother noted a dark red maculopapular rash starting at the hairline and spreading to the neck. Small white lesions are visible on the buccal mucosa. Which etiology is most likely responsible?
- A) Rubella virus infection
- B) Rubeola virus infection✓
- C) Parvovirus B19 infection
- D) Human herpesvirus six
💡 Key Takeaway
Measles (rubeola) is characterized by cough, coryza, conjunctivitis, Koplik spots, and a cephalocaudal rash.
Show rationale
The child is exhibiting the classic prodrome of rubeola virus (measles), which includes cough, coryza, conjunctivitis, and high fever. The small white lesions on the buccal mucosa are Koplik spots, which are pathognomonic for measles. The rash typically begins at the hairline and spreads downward. Rubella virus infection generally presents with milder systemic symptoms, prominent suboccipital adenopathy, and lacks Koplik spots. Parvovirus B19 infection causes erythema infectiosum, characterized by a slapped-cheek appearance and a lacy reticular rash on the body, without the severe respiratory prodrome. Human herpesvirus six causes roseola, where the rash typically begins on the trunk only after the fever has completely resolved, unlike this child who is still febrile with a descending rash.
Question 3
An 18-year-old female is in her third month of isotretinoin therapy. Her routine laboratory monitoring today reveals an AST of 145 U/L and ALT of 160 U/L. Her baseline hepatic panel was completely normal. What is the most appropriate intervention?
- A) Decrease the isotretinoin and recheck hepatic panel in two weeks.
- B) Discontinue the isotretinoin and recheck hepatic panel in two weeks.✓
- C) Decrease the isotretinoin and prescribe oral doxycycline for acne control.
- D) Discontinue the isotretinoin and prescribe oral doxycycline for acne control.
💡 Key Takeaway
Isotretinoin must be discontinued if liver transaminases exceed three times the upper limit of normal.
Show rationale
Isotretinoin can cause significant hepatotoxicity, and clinical guidelines mandate stopping the drug if transaminases exceed three times the upper limit of normal. Rechecking the labs ensures resolution of the acute liver injury. Options A and C are incorrect because simply decreasing the dose is unsafe with this degree of transaminase elevation; the offending agent must be stopped entirely. Option D is incorrect because combining or immediately following isotretinoin with tetracyclines like doxycycline significantly increases the risk of pseudotumor cerebri, making it a dangerous and contraindicated choice for alternative acne control in this immediate timeframe.
Question 4
A 2-year-old child who recently started daycare develops a fever, poor appetite, and a rash. The APRN notes painful shallow ulcers on the hard palate and tender papulovesicles on the lateral fingers.
- A) Atypical erythema multiforme allergic skin reaction
- B) Primary herpes simplex virus oral gingivostomatitis
- C) Classic hand, foot, and mouth disease✓
- D) Staphylococcal scalded skin syndrome clinical presentation
💡 Key Takeaway
Hard palate ulcers accompanied by tender finger papulovesicles confirm hand, foot, and mouth disease.
Show rationale
The combination of hard palate ulcers and tender papulovesicles on the lateral fingers is the classic presentation of classic hand, foot, and mouth disease, which is highly contagious in daycare settings. Atypical erythema multiforme allergic skin reaction is characterized by target lesions with a dusky center, rather than discrete papulovesicles on the fingers. Primary herpes simplex virus oral gingivostomatitis involves the anterior oral mucosa and causes friable, bleeding gums, but it lacks finger lesions unless complicated by a herpetic whitlow, which is usually a single, localized lesion. Staphylococcal scalded skin syndrome clinical presentation involves diffuse erythema, skin tenderness, and superficial blistering that sloughs off with gentle pressure, differing entirely from discrete oral and acral vesicles. Recognizing these specific lesion locations is crucial for accurate diagnosis.
Question 5
A 68-year-old reports severe allodynia over the right flank that disrupts sleep. The patient had a healed vesicular eruption four months ago in the exact same location. Which diagnosis is most appropriate?
- A) Acute herpes zoster flare
- B) Postherpetic neuralgia pain syndrome✓
- C) Secondary bacterial skin cellulitis
- D) Zoster sine herpete condition
💡 Key Takeaway
Postherpetic neuralgia is diagnosed when dermatomal neuropathic pain persists for more than ninety days after rash onset.
Show rationale
Diagnosis of postherpetic neuralgia is established when neuropathic pain persists for more than ninety days after the onset of an acute zoster rash. Since the patient's rash resolved several months ago, this is not an acute herpes zoster flare. Secondary bacterial skin cellulitis would present with new physical signs like expanding erythema, warmth, and swelling, which are entirely absent here. Zoster sine herpete condition involves dermatomal neuropathic pain without any preceding vesicular rash, making it incorrect since this patient clearly had a documented eruption four months prior.
Question 6
A 19-year-old with a known nickel allergy presents with an umbilical rash after wearing a new belt. Examination reveals an erythematous weeping base with honey-colored crusts and mild surrounding induration. Which exam finding most strongly indicates a secondary complication requiring a change in management?
- A) Erythematous weeping base on the lower abdomen
- B) Honey-colored crusting over the primary lesions✓
- C) Well-demarcated borders around the active rash
- D) Lichenified skin plaques near the central umbilicus
💡 Key Takeaway
Honey-colored crusting on an existing dermatitis indicates secondary impetiginization requiring targeted antibacterial therapy.
Show rationale
Honey-colored crusting is the hallmark sign of impetiginization, a secondary bacterial infection usually caused by Staphylococcus aureus or Streptococcus pyogenes. An erythematous weeping base and well-demarcated borders are expected primary findings in acute allergic contact dermatitis. Lichenification indicates chronic scratching but does not signify an acute secondary infection. Identifying the crusting changes the management plan to include antimicrobial therapy alongside dermatitis treatment.
Question 7
A 15-year-old male presents for a sports physical. The focused physical exam reveals numerous open and closed comedones on the forehead and nose, with less than five small erythematous papules on the cheeks. No nodules or scarring are present.
- A) Document the findings as mild acne vulgaris.✓
- B) Document the findings as moderate acne vulgaris.
- C) Document the findings as severe acne vulgaris.
- D) Document the findings as nodulocystic acne vulgaris.
💡 Key Takeaway
Mild acne vulgaris is characterized primarily by comedones with very few inflammatory lesions and no scarring.
Show rationale
The presentation of numerous comedones with fewer than five inflammatory papules and no scarring perfectly aligns with mild acne vulgaris. Moderate acne is characterized by a higher number of inflammatory papules and pustules, while severe or nodulocystic acne involves deep nodules, cysts, and significant scarring. Accurately grading the acne is essential for selecting the appropriate step-wise topical therapy.
Question 8
An 80-year-old male with baseline heart failure edema presents with unilateral right leg erythema that is exquisitely tender, warm, and weeping fluid. He denies recent travel or surgery.
- A) Acute deep vein thrombosis
- B) Acute bacterial skin cellulitis✓
- C) Chronic venous insufficiency flare
- D) Superficial venous thrombophlebitis
💡 Key Takeaway
Unilateral intense warmth and tenderness in a patient with baseline edema strongly suggest superimposed bacterial cellulitis.
Show rationale
Older adults with baseline edema from heart failure are at a significantly increased risk for acute bacterial skin cellulitis. When a patient develops unilateral intense warmth, exquisite tenderness, and weeping fluid, it strongly suggests an acute infection superimposed on chronic edema. An acute deep vein thrombosis certainly causes unilateral swelling, but it rarely produces the intense warmth or weeping fluid seen in this scenario. A chronic venous insufficiency flare can cause weeping, but it is typically a bilateral process and lacks the acute, exquisite tenderness described. Superficial venous thrombophlebitis presents as a firm, tender cord along a superficial vein rather than generalized weeping erythema. The unilateral inflammatory signs point directly to cellulitis.
Question 9
An 18-month-old presents with a faint pink descending rash. Examination reveals tender postauricular and suboccipital lymphadenopathy alongside a low-grade fever of 100.2°F. Which diagnosis is most likely?
- A) Rubeola virus infection
- B) Rubella virus infection✓
- C) Human herpesvirus 6
- D) Parvovirus B19 disease
💡 Key Takeaway
Rubella is characterized by a mild descending rash, low-grade fever, and prominent postauricular lymphadenopathy.
Show rationale
A mild descending rash paired with postauricular lymphadenopathy and low-grade fever is the hallmark of rubella. Rubeola also causes a descending rash but involves a high fever and severe respiratory prodrome. Human herpesvirus 6 causes roseola, which starts on the trunk after a high fever breaks. Parvovirus B19 typically begins with bright red cheeks before spreading to the extremities in a lacy pattern.
Question 10
24-year-old hiker in Connecticut presents with a 7-cm expanding annular rash with central clearing on his thigh, fatigue, and mild fever for 4 days.
- A) Order a two-tiered Lyme serology panel.
- B) Diagnose early localized Lyme disease clinically.✓
- C) Perform a skin biopsy of the lesion.
- D) Reassure the patient of a spider bite.
💡 Key Takeaway
An erythema migrans rash in an endemic area is sufficient for a clinical diagnosis without serologic testing.
Show rationale
A patient presenting with a classic erythema migrans rash in an endemic area like Connecticut requires a clinical diagnosis of early localized Lyme disease. Serologic testing is not recommended at this stage because antibodies take several weeks to develop, leading to false-negative results. Option A is incorrect because ordering a two-tiered serology panel delays treatment and is unnecessary when the pathognomonic rash is present. Option C is incorrect as a skin biopsy is invasive and not the standard of care for diagnosing this condition. Option D is incorrect because an expanding annular rash larger than 5 cm with systemic symptoms strongly points to a tick-borne spirochete infection, not a localized spider bite reaction. Recognizing the clinical presentation allows for prompt antibiotic initiation.
