Langerhans Cell Histiocytosis

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Case Summary

A 6-month-old female with no significant medical history initially presented to the emergency department with acute right eyelid swelling and redness. Ophthalmology was consulted and the patient was diagnosed with orbital cellulitis, which was treated with antibiotics. The redness and swelling initially improved but gradually returned in a few weeks. On the return visit to ophthalmology, there was no conjunctival infection, eye discharge, or fever. Magnetic resonance imaging (MRI) of the brain and orbits was recommended.

MRI demonstrated a mass along the right frontal bone involving the orbital roof, as well as an additional mass in the left orbital roof. These findings were concerning for Langerhans cell histiocytosis (LCH) or metastatic disease, and the patient was referred to oncology for further workup. A subsequent bone survey did not show any additional masses within the skeletal system. Biopsy was then obtained of the right orbital mass.

Imaging Findings

MRI demonstrated a heterogeneous mass in the right frontal bone involving the orbital roof, with overall T1 hypointensity with facilitated diffusion and regions of T2 hyperintensity. The mass demonstrated enhancement following intravenous administration of a gadolinium-based contrast agent (GBCA) (Figure 1). Another, smaller, mass in the left orbital roof was best visualized with a postcontrast T1 fat-saturation sequence. There were no intracranial masses or additional calvarial lesions, nor was there abnormal leptomeningeal enhancement. MRI of the orbits showed normal extraocular muscles and optic nerves, with no abnormal enhancement.

A subsequent computed tomography (CT) exam demonstrated that the masses were associated with osseous erosions within the frontal bones, the right superolateral orbit, and the inner table (Figure 2). The smaller mass in the left frontal bone caused scalloping of the inner table and erosion of the outer table.

Diagnosis

Langerhans cell histiocytosis

Discussion

Langerhans cell histiocytosis (LCH) is a rare granulomatous systemic disease that is more common in children than in adults. It can present as palpable masses, commonly involving the calvaria, skull base, and maxillofacial bones.¹The most common imaging finding is a well-defined skull lesion demonstrating significant GBCA enhancement on MRI and contrast-enhanced CT imaging, appearing as osteolytic masses on the latter. A bone survey should be performed to determine if other bones are involved. It is important to remember that LCH can present as single or multiple lesions.

LCH involvement of the central nervous system is less common; patients can be asymptomatic for years.^2,3These findings can include an enhancing mass within the tuber cinereum or infundibulum and absence of the T1 hyperintense posterior pituitary bright spot (Figure 3). This is best appreciated with a dedicated MRI scan of the pituitary that includes thin-section T1 postcontrast sequences with a GBCA. The clinical presentation typically accompanies diabetes insipidus.

Brain lesions can involve multiple regions and represent demyelination, best seen on T2/FLAIR sequences (Figure 4). The posterior fossa is a commonly associated region for LCH-related neurodegeneration; T1 hyperintense lesions of the dentate nuclei and globi pallidi can also be seen. While other histiocytic disorders affect the central nervous system, LCH is the most common. Other demyelinating processes such as acute disseminated encephalomyelitis (ADEM) are more common in children, and the history of LCH is important in accurately diagnosing neurodegenerative LCH.⁴

Conclusion

A well-defined lytic lesion involving the calvaria, skull base, or maxillofacial bones and displaying enhancement in the pediatric population should include LCH in the differential. Familiarity with CNS involvement of LCH can aid neuroradiologists in making an accurate diagnosis.

References

1. Lim SJ, Lim MK, Park SW, et al. Langerhans cell histiocytosis in the skull: Comparison of MR image and other images. JKSMRM. 2009;13:74-80.
2. Chaudhary V, Bano S, Aggarwal R, et al. Neuroimaging of Langerhans cell histiocytosis: A radiological review. Jpn J Radiol. 2013;31(12):786-796. doi:10.1007/s11604-013-0254-0.
3. Prayer D, Grois N, Prosch H, Gadner H, Barkovich AJ. MR imaging presentation of intracranial disease associated with Langerhans cell histiocytosis. Am. J. Neuroradiol. 2004;25: 880–891.
4. Prosch H, Grois N, Wnorowski M, Steiner M, Prayer D. Long-term MR imaging course of neurodegenerative Langerhans cell histiocytosis. Am. J. Neuroradiol. 2007; 28: 1022–1028.