How can I differentiate keratosis pilaris from other skin conditions with similar presentations?

Keratosis pilaris (KP) can be differentiated from other skin conditions with similar clinical presentations primarily by its characteristic appearance and distribution. KP typically presents as small, rough, follicular papules that are skin-coloured or slightly erythematous, often described as 'gooseflesh' or 'chicken skin'. These papules are usually found symmetrically on the extensor surfaces of the upper arms, thighs, and sometimes the cheeks, without significant inflammation or scaling ¹.

In contrast, other conditions such as folliculitis, eczema, or ichthyosis may present with more pronounced inflammation, scaling, or pustules. Folliculitis often shows pustular lesions centered on hair follicles with possible tenderness or pain, which is absent in KP ¹. Eczema typically involves more widespread erythema, scaling, and itching, often with a history of atopy, and lacks the uniform follicular papules seen in KP (Wang and Orlow, 2018). Ichthyosis presents with generalized scaling and dryness rather than discrete follicular papules (Wang and Orlow, 2018).

Additionally, KP lesions do not usually respond to antifungal or antibacterial treatments, which helps differentiate it from infectious follicular disorders ¹. The chronic, benign nature of KP, often improving with age, also contrasts with other dermatoses that may worsen or require more aggressive management (Wang and Orlow, 2018). Dermoscopy can aid diagnosis by revealing keratin plugs within hair follicles, a feature not typical of other conditions ¹.

In summary, the key differentiators of KP are its follicular, rough papules localized to typical sites, absence of significant inflammation or pustules, lack of response to antimicrobial therapy, and characteristic dermoscopic findings ¹ (Wang and Orlow, 2018).