How would you further investigate this patient?

1. Spirometry, lung volumes and DLCO measurement to assess lung function
2. Endocardial biopsy
3. Serum tryptase

What is the diagnosis?

Lymphocytic variant of hypereosinophilic syndrome. The presence of a TCR rearrangement alone is insufficient for a diagnosis of LV-HES, as clonal TCR can be seen in a variety of disease states, as well as normal people (Hodges et al.).

However, his clinical presentation and aberrant CD3 dim population of T cells is in keeping with a diagnosis of LV-HES.

What treatment would you institute, if any?

Oral prednisolone 1mg/kg/day. There is evidence to suggest that patients with LV-HES do well when treated with oral corticosteroids, with one case series reporting a CR (disappearance of symptoms) rate of over 70% in response to steroids. 

A number of patients will require steroid-sparing agents. A number of agents have been trialed. In a randomized controlled trial of 85 patients with hypereosinophilic syndromes, the use of mepolizumab (vs placebo) was associated with a significantly higher proportion of patients on doses of prednisolone < 10mg/day for 8 consecutive weeks to maintain a clinical response (Rothenberg et al., 2008).

A retrospective review of 188 patients with HES found that interferon-alpha was the most commonly used second-line agent, either due to corticosteroid failure or toxicity. The median maximal dose was 14 million units per week.

However, 87% of patients discontinued IFN, with the most common reason being medication intolerance. Of the 12 patients who used IFN as a monotherapy, 17% had CR and 33% had PR (Ougobu et al., 2010). Similar results have been seen with pegylated interferon (Butterfield et al., 2012).

Good to read: How I Treat Hypereosinophilic Syndromes (2015), The Lymphoid Variant of Hypereosinophilic Syndrome (2014).