Primary cutaneous amyloidosis is caused by the deposition of amyloid protein in the skin. Amyloid protein is a complex of globulin and mucopolysaccharides, named for its starch-like chemical reactions such as the iodine reaction, but it is actually unrelated to starch. Some suggest that this disease follows an autosomal dominant inheritance pattern. Abnormalities in blood lipids and proteins have been observed in some cases, indicating a possible link to metabolic disorders. A family history is present in some patients. It is more common in males than females, predominantly affecting young and middle-aged adults, and can persist for years or even decades.

bubble_chart Clinical Manifestations

1. It is more common in young and middle-aged adults, with a chronic course and intense itching;
2. The skin lesions are foxtail millet-sized keratotic dome-shaped papules, with a black keratin plug at the top. They appear hemispherical or polygonal, skin-colored or brown, with a rough surface. Removing the keratin plug reveals an umbilical depression;
3. It predominantly occurs on the extensor surfaces of the lower legs, followed by the back, behind the ears, and the outer sides of the arms;
4. When occurring on the back, it often presents as a reticular pigmented patch.

bubble_chart Diagnosis

1. Onset in young and middle-aged adults, with typical skin lesions and predilection sites.
2. Histopathological examination: Amyloid deposits mainly in the dermal papillary layer, appearing as light red, uneven, amorphous material with HE staining.

bubble_chart Treatment Measures

Treatment principles

1. There is no specific treatment; topical hormone ointment, salicylic acid ointment, sulfur ointment, etc., can be applied, followed by occlusion;
2. Small lesions can be treated with intralesional corticosteroid injections such as triamcinolone;
3. Oral antihistamines or procaine block therapy can be used to alleviate itching.

Medication principles

There are no specific drugs for this condition. Commonly used hormone-based medications are applied topically or taken orally to relieve symptoms.

bubble_chart Cure Criteria

1. Cure: Skin lesions subside by more than 90%, itching disappears;
2. Improvement: Skin lesions subside by more than 30%, most of the itching subsides;
3. No cure: Skin lesions subside by less than 30%.