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No pain and itching On whole body present Tell me the diagnosis
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Based on the image analysis and textbook evidence, here is the diagnosis:
Diagnosis: Lichen Amyloidosis (Primary Cutaneous Amyloidosis)
What the image shows
The image shows the ankle/distal lower leg of a dark-skinned individual with:
- Multiple deeply hyperpigmented, dark brown to grayish-black plaques and confluent patches
- Lichenified, dry, rough, thickened surface with fine scale
- Irregular, geographic borders with some areas fading into surrounding skin
- Background diffuse brownish hyperpigmentation
- Localized to the lower extremity (classic site for lichen amyloidosis)
Why Lichen Amyloidosis fits
| Feature in your patient | Classic lichen amyloidosis |
|---|---|
| Dark hyperpigmented plaques on shin/ankle | Most common site: shins and extensor surfaces |
| Firm, scaly, thickened, lichenified surface | Firm, scaly, hyperkeratotic papules coalescing into plaques |
| Present on whole body | Can have bilateral symmetric distribution over time |
| No pain | Can be asymptomatic or mildly pruritic |
| Background skin hyperpigmentation | Melanin-containing histiocytes surround amyloid deposits |
As stated in Dermatology 2-Volume Set 5e: "Lichen amyloidosis is the most common form of primary cutaneous amyloidosis and usually presents as persistent, pruritic plaques on the shins or other extensor surfaces. Initial lesions are discrete, firm, scaly, hyperpigmented papules, which later coalesce into plaques that often have a rippled or ridged pattern."
The asymptomatic (no pain, no/minimal itching) presentation on the ankle with whole-body involvement also raises the differential of macular amyloidosis or biphasic amyloidosis.
Differential Diagnoses to Consider
- Macular amyloidosis - more diffuse, flat, rippled pigmentation; often interscapular; can be asymptomatic
- Biphasic amyloidosis - overlapping features of both above (~15% of cases)
- Acanthosis nigricans - velvety hyperpigmentation, usually in body folds
- Post-inflammatory hyperpigmentation - after prior skin inflammation
- Venous stasis dermatitis - if confined to lower legs with edema history
Recommended Workup
- Skin biopsy - confirmatory; look for amyloid deposits in the papillary dermis
- H&E: eosinophilic, homogeneous deposits
- Congo red stain: apple-green birefringence under polarized light (pathognomonic)
- Crystal violet: metachromasia
- Rule out systemic amyloidosis if widespread or organ symptoms present (serum/urine protein electrophoresis)
Key Management Points
- Primary cutaneous amyloidosis is benign with no systemic involvement in most cases
- Treatment options: potent topical corticosteroids, tacrolimus, PUVA phototherapy, dermabrasion
- Condition is chronic and tends to persist; no curative treatment exists
- Patient reassurance is important
Note: This is a clinical assessment only. A skin biopsy with Congo red staining is required for definitive diagnosis. Please refer to a dermatologist.
Sources: Dermatology 2-Volume Set 5e (Ch. 47); Fitzpatrick's Dermatology, Vol. 1-2 (Ch. 125)
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