Minimal invasive biopsies are highly sensitive for amyloid detection in hereditary transthyretin amyloidosis with polyneuropathy.

Objective: To assess the effectiveness of labial minor salivary gland biopsy (LSGB) alone or in combination with punch skin biopsy (SB) for the detection of amyloid deposits in hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN).

Methods: In this single-center retrospective study, Congo red staining of minimal invasive LSGB (4 mm) and SB (3 mm) was assessed in ATTRv-PN patients consecutively evaluated between 2012 and 2023.

Results: Histopathological data of 171 ATTRv-PN, including 49 early-onset p.Val50Met, 58 late-onset p.Val50Met, and 64 non-p.Val50Met, were reviewed. LSGB and SB identified amyloid deposits in 123/171 (72%) and 131/171 (77%) patients respectively (p = 0.2). Combining LSGB and SB increased the amyloid detection rate to 150/171 (88%), especially in late-onset p.Val50Met (48/58 [83%]) and non-p.Val50Met patients (55/64 [86%]). LSGB and SB have a similar rate of detection of amyloid depositions in early onset p.Val50Met patients (94%). Also, the LSGB/SB combination identified amyloidosis in 89% (55/62) of early-stage ATTRv-PN patients.

Conclusions: In our study, combining LSGB and SB allowed the detection of amyloid deposits in 88% of ATTRv-PN patients. LSGB/SB analysis may be of major interest to confirm entry in the disease at very early-stage ATTRv-PN, with implications in disease-modifying treatment initiation.