Langerhans cell histiocytosis (LCH) is a rare clonal proliferative disease that can involve one or more organs (1). In adults, multisystem involvement is generally predominant (68.6%), whereas single-system involvement is less common (2). The clinical spectrum is broad, with bone, skin, and lungs being the most frequently affected organs. The treatment approach varies according to the extent of the disease, and the optimal treatment strategy has not yet been clearly defined(3-6).

This study aimed to evaluate the demographic characteristics, sites of involvement, treatments administered, and treatment responses of adult LCH cases diagnosed at our center.

Medical records of adult patients diagnosed with LCH at our center between 2002 and 2024 were retrospectively reviewed. Patient age, sex, sites of involvement, treatment regimens, treatment responses, and follow-up durations were recorded.

A total of 10 patients (9 male, 1 female) were analyzed. The median age was 31.5 years (range: 20–76). The median follow-up duration was 5.8 years (approximately 69 months). Three patients (30%) had multisystem involvement, and seven patients (70%) had single-system involvement. The most common site of involvement was bone (80%), followed by skin (20%) and lymph nodes (10%). Diabetes insipidus was detected in one patient (10%).

Treatment approaches were heterogeneous. Five patients received radiotherapy (RT), three patients were treated with a vinblastine and prednisolone combination, one patient with multisystem involvement received cladribine combined with RT, one patient was given prednisolone monotherapy, and one patient was followed without treatment.

A response was achieved in all patients after initial treatment. Two patients (20%) experienced relapse, both in those with bone involvement only. The patient treated with cladribine remains in long-term complete remission. No mortality was observed.

Feature

Value

Total number of patients

10

Median age (years)

31.5 (20–76)

Median follow-up duration

5.8 years (approximately 69 months)

Male/Female

9/1

Multisystem

3 (30%)

Single-system

7 (70%)

Most common involvement

Bone (80%)

Relapse

2 (20%)

Mortality

0

In adult Langerhans cell histiocytosis, multisystem involvement is reported as the most common form in the literature; however, in our study, single-system involvement was detected in 70% of patients. This discrepancy may be explained by differences in patient referral patterns to our center, follow-up of pulmonary LCH cases in chest disease clinics, variations in staging due to the retrospective design, and demographic factors.The complete remission rate with vinblastine and prednisolone combination therapy is reported to be approximately 70% in the literature (6). In our series, all three patients treated with this regimen achieved complete remission. Cladribine, a purine analog, is an effective option in refractory or relapsed cases; in the literature, monotherapy with cladribine has been reported to achieve a complete remission rate of approximately 50% and an overall response rate of approximately 90% (5). In our series, the patient treated with cladribine achieved long-term complete remission. The relapse rate in our study was 20%, consistent with the 20–30% range reported by Néel et al. (5).

Although Langerhans cell histiocytosis is a rare disease, long-term complete remission can be achieved with appropriate treatment. In our study, all patients achieved a response, and the relapse rate was 20%, consistent with the literature. Multisystem involvement is a risk factor for relapse. The patient treated with cladribine achieved long-term complete remission. Larger, multicenter prospective studies are needed to optimize treatment strategies in Langerhans cell histiocytosis.