Atypical multicentric reticulohistiocytosis in an elderly male patient

ABSTRACT
Multicentric reticulohistiocytosis (MRH) is a rare systemic proliferative granulomatous disease of non-Langerhans cells. The aim of this study is to report a case of multicentric reticulohistiocytosis that is easily misdiagnosed in clinical practice. A 74-year-old man sought the Rheumatology office in December 2022 with a main complaint of arthralgia for six months, associated with morning stiffness, joint swelling, and upper and lower limb weakness. On physical examination, papules on the dorsal surface of the proximal interphalangeal joints, base of the nose, and lateral surface of the right hallux were observed. Hyperemia was also identified on the back, and edema of the proximal and distal interphalangeal joints, wrists and knees. Laboratory tests revealed ESR and ANA within normal limits. Tests were negative for Anti-Sm, Anti-RO, rheumatoid factor, Anti-CCP, HIV, and HCV. Chest CT-scan showed right axillary lymph node enlargement, measuring 2.7 cm, atheromatous aorta, and streaks with scattered atelectasis in the lower lobe, without other changes. On total abdominal ultrasound, prostate enlargement was detected. Immunohistochemistry of skin biopsy identified atypical acinar proliferation. Histopathology skin biopsy stained with hematoxylin-eosin (January 2023) showed a dense histiocytic infiltrate. Detail of the histiocytic component displayed “ground glass” eosinophilic cytoplasm. Immunohistochemistry was negative for S100 and CD34 and positive for CD68. Final diagnosis was MRH. The patient underwent treatment with drugs. In conclusion, clinical manifestations, including skin and joint changes, with signs and symptoms of rheumatic disorders (e.g. dermatomyositis and rheumatoid arthritis) similar to those of MRH are expected in rheumatology practice. However, knowledge about disease progression in MRH is limited. Therefore, this case report is described due to its rarity 
Keywords: Non-Langerhans-Cell Histiocytosis, Pathology, Muticentric Reticulohistiocytosis, Rheumatological Diseases,