How is Hyper-IgD Syndrome / Hyperimmunoglobulinemia D With Recurrent Fever (HIDS) diagnosed?

Hyper-IgD Syndrome, also known as Hyperimmunoglobulinemia D with Recurrent Fever (HIDS), is a rare genetic disorder characterized by recurrent episodes of fever accompanied by various symptoms. Diagnosing HIDS can be challenging due to its similarity to other inflammatory conditions. However, a combination of clinical evaluation, genetic testing, and laboratory investigations can help in confirming the diagnosis.

Clinical Evaluation

The first step in diagnosing HIDS involves a thorough clinical evaluation by a healthcare professional. The doctor will review the patient's medical history, including the frequency, duration, and characteristics of fever episodes. They will also assess the presence of other symptoms such as abdominal pain, joint swelling, skin rashes, and lymph node enlargement. The doctor may ask about family history, as HIDS is an inherited disorder.

Genetic Testing

Genetic testing plays a crucial role in diagnosing HIDS. It involves analyzing the patient's DNA to identify mutations in the mevalonate kinase (MVK) gene, which is responsible for the production of an enzyme involved in the body's inflammatory response. A blood sample is usually collected for genetic testing, and the DNA is examined using techniques like polymerase chain reaction (PCR) or gene sequencing. The presence of specific mutations in the MVK gene confirms the diagnosis of HIDS.

Laboratory Investigations

Several laboratory tests can support the diagnosis of HIDS by assessing the levels of certain markers in the blood during fever episodes. These tests include:

• Acute-phase reactants: Blood tests measuring markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) can indicate the presence of inflammation during fever episodes.


• IgD levels: Hyperimmunoglobulinemia D is characterized by elevated levels of IgD, an immunoglobulin involved in the immune response. Blood tests can measure IgD levels during fever episodes.


• Mevalonic acid: Measuring the levels of mevalonic acid, a byproduct of the faulty enzyme produced in HIDS, can help support the diagnosis.


• Other inflammatory markers: Additional tests may be performed to assess the levels of interleukin-1 beta (IL-1β) and other inflammatory markers, as their elevation is often observed in HIDS.

Differential Diagnosis

Since HIDS shares symptoms with other inflammatory conditions, it is important to rule out alternative diagnoses. Conditions such as familial Mediterranean fever (FMF), systemic juvenile idiopathic arthritis (SJIA), and other autoinflammatory disorders may present similar symptoms. The clinical evaluation, genetic testing, and laboratory investigations help differentiate HIDS from these conditions.

Conclusion

Diagnosing Hyper-IgD Syndrome / Hyperimmunoglobulinemia D with Recurrent Fever (HIDS) involves a comprehensive approach that combines clinical evaluation, genetic testing, and laboratory investigations. The identification of specific mutations in the MVK gene through genetic testing is crucial for confirming the diagnosis. Additionally, assessing the levels of acute-phase reactants, IgD, mevalonic acid, and other inflammatory markers aids in supporting the diagnosis. It is important to differentiate HIDS from other similar conditions through a thorough evaluation to ensure appropriate management and treatment.