From the Guidelines
Diagnosing histiocytosis in the ear requires a comprehensive approach involving clinical evaluation, imaging studies, and biopsy confirmation, as outlined in the Mayo Clinic Histiocytosis Working Group consensus statement 1. The diagnostic process typically begins with a thorough physical examination of the ear, looking for signs such as otorrhea, granulation tissue, polyps, or hearing loss. Otoscopic examination may reveal characteristic lesions or tissue changes.
Key Diagnostic Steps:
- Imaging studies, particularly CT and MRI scans, are essential to assess the extent of disease, bone involvement, and soft tissue abnormalities.
- The definitive diagnosis requires a biopsy of the affected tissue, which should be examined histologically for the presence of histiocytes and immunohistochemical markers such as CD1a, S100, and CD207 (Langerin) for Langerhans cell histiocytosis, or other specific markers depending on the histiocytosis subtype.
- Laboratory tests including complete blood count, liver function tests, and coagulation studies may help evaluate systemic involvement.
- Audiometric testing is important to assess hearing function. Early diagnosis is crucial as histiocytosis can cause significant local destruction and hearing impairment if left untreated, and the condition may represent either a localized process or part of a multisystem disorder requiring comprehensive management. According to the Mayo Clinic Histiocytosis Working Group consensus statement 1, the diagnosis of histiocytic neoplasms, including Erdheim-Chester disease, Langerhans cell histiocytosis, and Rosai-Dorfman disease, is often delayed due to their rarity and diverse clinical manifestations.
Important Considerations:
- The presence of central diabetes insipidus and bony pain in the absence of other etiologies should raise suspicion for Erdheim-Chester disease and Langerhans cell histiocytosis 1.
- The pathognomonic radiographic finding of Erdheim-Chester disease is metadiaphyseal osteosclerosis around the knees, which can be elicited on vertex-to-toes (full-body) PET-CT or technetium-99m bone scintigraphy 1.
- Molecular profiling using target capture next-generation sequencing for MAPK/ERK and PI3K/AKT pathway gene mutations can help establish the diagnosis of histiocytic neoplasms, especially in patients with nonclassic phenotypes or unclear histopathologic features 1.
From the Research
Diagnosis of Histiocytosis in the Ear
To diagnose histiocytosis in the ear, the following steps can be taken:
- Physical examination to check for symptoms such as edema in the tympanic membrane and external ear canal, and pain by palpation in the mastoid area bilaterally 2
- Temporal bone high resolution computed tomography (CT) to show lesions causing erosion in the mastoid cortex, tegmen tympani, ossicles, and in the bone covering the sigmoid sinus bilaterally 2
- Histopathologic examination of the tissue to reveal Langerhans cell histiocytosis (LCH) 2
- Functional imaging with fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT to detect increased metabolic activity in histiocytes and provide a comprehensive whole-body evaluation of potential involvement with multiple organ systems 3
- Biopsy specimens infiltrated by histiocytes to check for somatic mutations in genes activating the MAP kinase cell-signalling pathway 4
Imaging Features
Imaging features of histiocytosis in the ear may include:
- Erosion in the mastoid cortex, tegmen tympani, ossicles, and in the bone covering the sigmoid sinus bilaterally 2
- Erosion in the superior semicircular canal and petrous bone 2
- Increased metabolic activity in histiocytes on FDG PET/CT 3
Clinical Manifestations
Clinical manifestations of histiocytosis in the ear may include: