A rare differential for sinusitis and visual loss.

Area of Science:

• Histiocytic Disorders
• Rare Diseases
• Molecular Diagnostics

Background:

• Erdheim-Chester disease (ECD) is a rare, systemic histiocytic disorder characterized by non-Langerhans cell histiocyte infiltration.
• While skeletal involvement is most common, ECD can affect multiple organs, presenting diagnostic challenges.
• The global reported incidence of ECD is approximately 800 cases.

Observation:

• A rare case of Erdheim-Chester disease presenting with sinus infiltration and subsequent vision impairment is detailed.
• The patient, an ex-Royal Air Force pilot, experienced vision loss attributed to the disease's unusual manifestation.
• Diagnostic delays were encountered due to the atypical presentation.

Findings:

• Repeated molecular testing, specifically polymerase chain reaction (PCR) analysis, was crucial for diagnosis.
• Identification of the BRAF V600 mutation was the key molecular finding.
• This mutation confirmed the diagnosis of Erdheim-Chester disease in this patient.

Implications:

• Highlights the importance of considering rare presentations of Erdheim-Chester disease, even with atypical symptoms like vision loss.
• Emphasizes the diagnostic utility of molecular testing, particularly for identifying the BRAF V600 mutation in challenging cases.
• Suggests that early identification of specific mutations can expedite diagnosis and potentially guide treatment strategies for ECD.