Clinicopathological Study of Primary Cutaneous Amyloidosis in a Tertiary Care Center of Eastern India Reveals Insignificant Association with Friction, Scrubbing, and Photo-Exposure: How valid is the "Keratinocyte Hypothesis"?

INTRODUCTION: Primary cutaneous amyloidosis (PCA) can be classified into four principal categories: macular amyloidosis, lichen amyloidosis, biphasic, and nodular amyloidosis. Some unusual variants such as widespread diffuse hyperpigmentation without papules, poikiloderma like involvement, lesions following Blaschko's line, etc., have also been reported. However, not much data are available regarding the demography, epidemiology, clinical patterns, and distribution and histopathological findings, especially from the eastern part of India. AIMS: We conducted a cross-sectional, institution-based study to evaluate clinicopathological pattern and factors of PCA in eastern India. MATERIALS AND METHODS: We recorded clinical and histopathological findings of 100 consecutive patients of PCA presenting to a tertiary care institution of Kolkata in eastern India. RESULTS: We found female patients of PCA outnumber male (M:F =1:1.9) with majority of patients being young adults (56%) between 20 and 40 years of age. More than half (54%) of the patients were pruritic. The severity of pruritus is significantly more associated with lichenoid and biphasic variants over macular amyloidosis. Positive family history was recorded in 17% of cases. Macular variant was the most common variant constituting 48% of the total PCA. We also found that the association with history of friction and scrubbing and photo-exposure were statistically insignificant. However, duration of the disease has statistically significant association with the disease morphology. Congo red stain showed these deposits as reddish orange substance in 28 patients out of 64 patients' samples on which Congo red could be performed. CONCLUSION: Our study revealed that many concepts of pathogenesis of PCA including friction and photoexposure might have lesser importance. However, morphological types were significantly associated with the duration of the disease and symptom severity.