What Are Papules
Papules are small, solid, raised skin lesions typically less than 1 cm in diameter that are elevated above the surrounding skin surface without containing visible fluid.
Basic Definition and Characteristics
Papules represent a fundamental morphologic description in dermatology rather than a specific diagnosis. They are:
- Solid elevations of skin that are palpable and raised above the skin surface 1
- Small in size, generally defined as less than 1 cm in diameter 1
- Non-fluid containing, distinguishing them from vesicles or pustules 1
- Variable in appearance, ranging from skin-colored to erythematous (red), white, or pigmented depending on the underlying cause 1
Clinical Context and Evolution
Papules often represent an early or intermediate stage in the evolution of various skin conditions:
- In nonbullous impetigo, lesions begin as papules that rapidly evolve into vesicles surrounded by erythema, then become pustules before breaking down to form characteristic thick crusts over 4-6 days 1
- In immunotherapy-related skin reactions, papules may appear as erythematous lesions that can progress to lichenoid eruptions or other patterns 1
- In HPV-related conditions, papules may present as slightly elevated, minimally keratinized lesions (as in multifocal epithelial hyperplasia) or as papillary projections (in condyloma acuminatum) 1
Common Causes of Papular Eruptions
Infectious Etiologies
- Cryptococcal infections in immunosuppressed patients can manifest as papules resembling molluscum contagiosum lesions 1
- Follicular infections may present as inflammatory papules before progressing to furuncles 1
Inflammatory and Drug-Related
- Anticancer therapy (EGFR inhibitors, MEK inhibitors) commonly causes follicular papules and pustules, particularly in sebaceous-rich areas like the face 1
- Immunotherapy can trigger papulosquamous eruptions, lichenoid papules, or sarcoid-like granulomatous papules 1
Other Presentations
- Keratosis pilaris presents as small folliculocentric papules with perifollicular erythema 2
- Polymorphous light eruption can manifest as small papules ranging to large papules that coalesce into plaques 3
Critical Clinical Pitfall
When evaluating papular eruptions, particularly in specific anatomic locations or patient populations, always consider serious underlying conditions:
- Papules around the breast require imaging evaluation to exclude inflammatory breast cancer before assuming a benign diagnosis 4
- In immunosuppressed patients, papular lesions may represent disseminated fungal or cryptococcal infection requiring aggressive workup 1
- Facial papules in certain contexts may indicate internal malignancy and warrant biopsy for definitive diagnosis 5
Diagnostic Approach
The specific cause of papules cannot be determined by morphology alone and requires:
- Clinical context: location, distribution, associated symptoms, patient immune status, medication history 1
- Evolution pattern: how the lesions developed and changed over time 1
- Skin biopsy: often necessary for definitive diagnosis, particularly when malignancy or systemic disease is suspected 4, 5
- Culture: indicated when infectious etiology is suspected 1