1. Pityriasis versicolor (tinea versicolor), hyperpigmented/mixed variant
   • Commonly affects upper trunk and back.
   • May be asymptomatic and persistent.
   • Fine scale becomes clearer on gentle scraping/stretching.
   • Can show mixed hypo- and hyperpigmentation. DermNet’s clinical description is consistent with this distribution and appearance.

1. Confluent and reticulated papillomatosis (CARP)
   • Brown, scaly, slightly papillomatous plaques that become confluent centrally with a reticulate edge, typically on the upper trunk.
   • More usual in younger individuals, but should be considered if KOH is negative and the plaques have a reticular/papillomatous surface.
2. Macular amyloidosis
   • Upper-back hyperpigmentation, often with a rippled pattern.
   • Usually pruritic and without true fine fungal scale, so less likely here.
3. Pityriasis rotunda / acquired ichthyosiform scaling
   • Well-defined, round or oval, dry scaly hyperpigmented trunk plaques.
   • In an older adult with new-onset persistent lesions, confirm clinically and consider biopsy if atypical or refractory.
4. Dermatophytosis (tinea corporis)
   • Less likely without an annular advancing active edge or central clearing, but should be excluded on microscopy.
5. Seborrhoeic dermatitis or chronic eczematous dermatitis
   • Less likely given the relatively discrete upper-back plaques and minimal inflammation.

Useful bedside confirmation

• Scrape scale from the most scaly area for 10% KOH microscopy. Pityriasis versicolor shows short hyphae and yeast cells, classically described as “spaghetti and meatballs.”
• Wood lamp may show yellow-green/pale fluorescence, but a negative result does not rule it out.
• If KOH is negative or lesions do not respond as expected, examine for reticulation/papillomatosis and consider dermoscopy or punch biopsy to distinguish CARP, macular amyloidosis, and pityriasis rotunda.

1. Confluent and reticulated papillomatosis (CARP, Gougerot-Carteaud disease)
   • Best clinical fit if there is a subtly verrucous or papillomatous texture, with central confluent plaques and peripheral reticulation.
   • Classically upper trunk, interscapular region, neck, and axillae; lesions are often asymptomatic.
   • Age 60 is unusual, but not exclusionary. Textbook descriptions include hyperpigmented verrucous papules that form reticulated plaques.
   • Confirm by negative KOH/mycology; biopsy is useful in this age group or if the morphology is atypical. CARP diagnostic features include papillomatous brown plaques on the upper trunk with fungal studies negative.
2. Macular-lichen amyloidosis / biphasic primary localized cutaneous amyloidosis
   • Upper back is a favored site for macular amyloidosis.
   • A rippled hyperpigmented background with superimposed keratotic papules would support lichen or biphasic amyloidosis.
   • Pruritus and habitual rubbing are common but not obligatory.
3. Seborrhoeic keratosis, especially multiple/clustered or plaque-type lesions
   • Consider if the surface is greasy, cerebriform, “stuck-on,” or verrucous.
   • The broad bilateral plaques seen here are less typical than discrete lesions.
4. Epidermal nevus, late-recognized / verrucous epidermal nevus
   • A hyperkeratotic papillomatous plaque is possible, although it usually begins much earlier in life and often follows Blaschko lines.
5. Acanthosis nigricans or acquired papillomatous acanthosis
   • Consider only if there is similar velvety thickening on the neck, axillae, groin, or other flexures. Isolated scapular involvement would be atypical.
6. Bowen disease / superficial squamous neoplasia
   • Not the leading possibility if lesions are bilateral, similar, and stable, but in a 60-year-old, a newly acquired persistent raised scaly plaque should not be assumed benign without dermoscopy or biopsy, especially if there is induration, focal ulceration, bleeding, marked asymmetry, or progressive enlargement.

Practical next step

• CARP: papillomatosis, hyperkeratosis, acanthosis with basal hyperpigmentation
• Amyloidosis: papillary dermal amyloid, confirmed with Congo red if needed
• Seborrhoeic keratosis/epidermal nevus
• Intraepidermal neoplasia if clinically concerning