DP04 Follicular and cutaneous keratotic spicules along with naevoid hyperkeratosis of the nipple and areola: a window to diagnose multiple myeloma
Authors: None Priyanka, Biswanath Behera
Journal: British Journal of Dermatology (2024)

Abstract A 73-year-old man presented with asymptomatic skin lesions over the face, followed by the trunk and bilateral arms for 3 months. Cutaneous examination revealed multiple follicle-based skin-coloured to whitish-yellow dome-shaped to spiny keratotic papules on the face, clustered on the dorsal surface of the nose. Multiple reddish-brown keratotic papules and plaques were seen on the bilateral arms and chest. Similar keratotic papules were located on the bilateral nipple and areola, resulting in naevoid hyperkeratosis. Dermoscopy of follicular spicules showed dilated follicular ostia with yellow to yellow–white keratotic plug, and the cutaneous lesions showed a target pattern with the central brown structureless area surrounded by a white rim. The differential diagnoses considered were paraneoplastic disseminated porokeratosis, and follicular and cutaneous spicules due to multiple myeloma (MM). Histopathology of the skin biopsy showed parakeratotic hyperkeratosis, acanthosis, papillomatosis and amorphous eosinophilic deposition in the interkeratinocyte space in the epidermis. Immunohistochemistry of amorphous material was positive for lambda light chains and negative for kappa light chains. Blood investigations revealed pancytopenia and increased serum proteins and globulin levels, with reversal of the albumin globulin ratio (−1 : 3.2). Further investigations revealed osteolytic lesions of multiple vertebrae, ribs and clavicle. Serum protein electrophoresis showed a monoclonal ‘M’ spike in the gamma-globulin region, thus confirming the diagnosis of MM. Skin involvement in MM can be specific or nonspecific based on direct or indirect skin infiltration by proliferating plasma cells or their products. Follicular spicules of the nose and face have been reported as a very specific and rare manifestation of multiple myeloma. In most cases, cutaneous and follicular spicules were the initial presentation and pointed to the diagnosis. The eosinophilic amorphous deposition represents the precipitation and accumulation of IgG proteins and cryoglobulins in the interkeratinocytic and follicular epithelium. The clinical presentation mimics trichodysplasia spinulosa very closely. Van Boheemen et al. argued in favour of this by demonstrating complete clearance of spicules with topical cidofovir gel (van Boheemen S, Jones T, Muhlemann B et al. Cidofovir gel as treatment of follicular spicules in multiple myeloma. JAMA Dermatol 2015; 151: 82–4). In contrast, Hosler et al. failed to demonstrate viral particles despite using multiple primer sets (Hosler GA, Weibel L, Wang RC. The cause of follicular spicules in multiple myeloma. JAMA Dermatol 2015; 151: 457–8). Besides, skin lesions improved with lenalidomide used for systemic disease. In conclusion, this case highlights the uniqueness of follicular and cutaneous keratotic spicules and their role in revealing the diagnosis of MM. In addition, we report naevoid hyperkeratosis of the nipple and areola, a rare cutaneous presentation of MM.