Clinical skin photograph showing numerous small erythematous papules and pustules distributed across trunk/back. The lesions are centered on hair follicles, 2–5 mm in diameter, with surrounding perifollicular erythema and occasional crusting. The overall pattern is diffuse and crops of lesions are evident, consistent with folliculitis. This presentation is classically associated with Pseudomonas aeruginosa infection, often termed hot tub folliculitis, though other gram-negative organisms can cause a similar eruption. Incubation after warm water exposure is typically 24–48 hours. The image demonstrates superficial involvement of the follicular unit without deeper necrosis; no comedones are evident; there is mild edema of the surrounding skin. The phototype appears light to moderate; however, color fidelity is preserved, aiding assessment of vascular dilation and inflammation. Clinically, a history of recent hot tub, pool, or whirlpool exposure should be elicited; pustule cultures or Gram stain can confirm Pseudomonas. Management is usually supportive, with spontaneous resolution in days to weeks; antibiotics with anti-pseudomonal activity are reserved for persistent or extensive disease or immunocompromised patients. These images are suitable for medical education, case repositories, and digital dermatology teaching materials.

Clinical photography of the upper back and left shoulder/scapular region illustrating a mild inflammatory dermatosis. Modality: clinical photography; perspective: posterior dorsal view. The skin shows multiple small erythematous papules, several with central pustules, clustered along the upper thoracic/scapular zone. Lesions measure approximately 2–4 mm in diameter and are discrete but in close proximity, consistent with a follicular pattern. No significant crusting or scarring is evident; surrounding skin is otherwise uninvolved. The appearance is suggestive of an acneiform eruption or folliculitis, with inflammatory insult centered on hair follicles. Differential diagnoses include acne vulgaris of the back (bacne), folliculitis (bacterial or fungal), keratosis pilaris-like follicular papules, insect bites, or contact dermatitis. The lesions' symmetry and distribution favor follicular inflammation in regions with higher sebaceous gland density and tolerated occlusion. Clinically, this presentation may respond to topical anti-inflammatory agents, benzoyl peroxide, or topical retinoids if cosmetic concerns persist; antibiotic therapy may be considered for secondary infection. Correlation with patient history (pubertal status, hormonal fluctuations, sweating, clothing friction, recent hygiene products) and possible Gram stain or culture if lesions enlarge or fail to improve can guide management. This image highlights common back acne patterns and serves educational purposes for recognition and differential diagnosis. education.

Imaging modality and technique: Clinical photography in color, dorsal posterior trunk view, standard ambient lighting with minimal glare; no dermatoscopic enhancement or chemical staining. The specimen is human skin surface. The primary subject is the back of an adolescent or adult individual presenting an acneiform eruption. The image shows multiple erythematous papules scattered across the upper back and shoulder regions, with a subset displaying central pustulation and a follicular distribution pattern. Lesions vary from small target-like pustules to larger inflamed papules, some with slight crusts, and there is minimal surrounding edema. The overall appearance is consistent with inflammatory acne involving the trunk, with folliculitis-like features at several sites. No open comedones or nodules are clearly evident in this view, though clinically these may be present elsewhere. The background is clear, allowing visualization of lesion morphology, distribution, and degree of surface inflammation. This photographic documentation is suitable for tracking lesion response to therapy, counseling patients, and aiding dermatologic differential diagnosis, including acne vulgaris of the trunk, folliculitis, and less likely keratosis pilaris sparing the trunk. The image lacks histopathology data and laboratory correlation; a clinical diagnosis should be confirmed with history, examination, and, if needed, culture or biopsy.