Multicentric reticulohistiocytosis in children: two case reports and a literature review

Multicentric reticulohistiocytosis (MRH) is a disease of unknown etiology that predominantly affects middle-aged and elderly women. Although it can manifest with multi-organ involvement, characteristic skin rashes often aid in the diagnosis. MRH is rare in children and may be misdiagnosed as conditions such as juvenile idiopathic arthritis (JIA). We report two male pediatric cases: a 10.8-year-old boy (case 1) presenting with polyarthritis, coral‑bead‑like papules, and subcutaneous nodules, and a 14-year-old boy (case 2) with a prior diagnosis of systemic-onset JIA complicated by macrophage activation syndrome, who presented with persistent atypical pruritic rashes unresponsive to conventional and biologic therapies. Both cases were confirmed as MRH by skin biopsy, and tofacitinib demonstrated good efficacy in alleviating the symptoms. JIA is a diagnosis of exclusion. If a child presents with arthritis along with other atypical manifestations, such as skin rashes, a skin biopsy should be performed to further investigate. The goal is to explain all clinical features with a single underlying diagnosis whenever possible. Key Points • Suspect MRH in children with polyarthritis and coral bead‑like papules. Even if inflammatory markers (ESR, CRP) are normal, the combination of arthritis and characteristic skin lesions warrants a skin biopsy. • Histopathological examination plays a key role in the diagnosis of MRH. Histopathology shows CD68+/CD163+ histiocytes with "ground‑glass" cytoplasm and multinucleated giant cells, while S‑100 and CD1a are negative (non‑Langerhans cell histiocytosis). • Early aggressive immunosuppression may prevent joint damage. Early use of corticosteroids in combination with conventional DMARDs represents the cornerstone of management for MRH, offering effective control of mild-to-moderate disease activity. In cases where conventional treatment fails, is not tolerated, or results in recurrence, biologic therapies-such as TNF-α inhibitors, JAK inhibitors, and IL-6 receptor antagonists-may be viable alternative options.