The challenging diagnosis of isolated cardiac sarcoidosis.

Godo et al.[1] reported in your Journal a nicely written and well-illustrated case of isolated cardiac sarcoidosis (CS) with coronary vasomotion abnormalities. The only problem is that the patient may not have had CS. The diagnosis rests on the Japanese diagnostic criteria for isolated CS[2] which remain unvalidated and are thus susceptible to criticism.[3,4] These criteria substitute the combination of certain clinical cardiac manifestations with findings on 18-F fluorodeoxygenase positron emission tomography (FDG PET) and cardiac magnetic resonance (CMR) for histology of sarcoid granulomas in the heart.[2] Unfortunately, FDG PET and CMR have limited specificity for CS in the absence of signs of extracardiac sarcoidosis. In an important study, Divakaran et al.[5] compared pretransplant findings on PET and CMR with the histology of explanted hearts, the only valid standard for the diagnosis of CS. Among their nine patients with FDG uptake on PET compatible with isolated CS (cardiac FDG uptake without extracardiac activity), only one patient had myocardial histology of CS, the rest having arrhythmogenic, dilated, hypertrophic, and restrictive cardiomyopathies or lymphocytic myocarditis. Likewise, only one of their eight patients with CMR abnormalities suggestive of probable or highly probable CS had sarcoid granulomas in the explanted heart. Due to the restricted specificity of cardiac imaging for isolated CS, and because fatal ventricular arrhythmias, wall motion abnormalities, and disordered conduction are possible also in other, more common, myocardial diseases, the patient of Godo et al.[1] may well have suffered from some other form of underlying myocardial inflammation. The authors should have acknowledged this limitation of their report.

Conflict of interest: None declared.

Funding: None declared.