NIH Rare Diseases

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.Orpha Number: 137675Disease definitionHistiocytoid cardiomyopathy is an arrhythmogenic disorder characterised by cardiomegaly, severe cardiac arrhythmias or sudden death, and the presence of histiocyte-like cells within the myocardium. The prevalence is unknown but less than 100 patients have been described in the literature so far. The majority of reported cases involved children under 2 years of age with a female:male ratio of 3:1. Clinically, the disease may manifest as various types of incessant arrhythmia (including atrial and ventricular fibrillation, supraventricular and ventricular tachycardia and Wolff-Parkinson-White syndrome; see this term) but sudden death due to cardiac arrest is a common presentation. Association with other cardiac defects (ventricular and atrial septal defects, hypoplastic left heart syndrome and endocardial fibroelastosis; see these terms) and with extracardiac anomalies (hypotonia, MIDAS syndrome, Peter's anomaly and congenitalglaucoma; see these terms) has also been reported. Histiocytoid cardiomyopathy was largely suspected to be caused by a developmental anomaly of the conduction system, however, a mtDNAmutation in the gene encoding mitochondrial cytochrome b ( MT-CYB) has been identified. In familial cases (5% of reported patients), inheritance appears to be autosomal recessive but X-linked transmission has also been suggested in patients with the association of histiocytoid cardiomyopathy and MIDAS syndrome (an X-linked dominant condition caused by mutations in the HCCS gene localised to Xp22). The histological findings are pathognomonic for the disease with yellow-tan nodules in the myocardium and, in some cases, in the subendocardial and subepicardial areas. The nodules are composed of nests of foamy histiocyte-like cells with a granular cytoplasm containing lipid droplets and abundant atypical mitochondria. These abnormal myocytes are found mainly in the ventricles but involvement of the valves has also been reported. As sudden infant death is frequently the presenting manifestation, sudden infant death syndrome (SIDS) is often the initial diagnosis in these cases but can be ruled out by histological evaluation of the myocardial tissue. Management options for patients presenting with arrhythmias include surgical removal of the nodular lesions, and electrophysiological mapping and radiofrequency ablation of the arrhythmias. Antiarrhythmics are generally ineffective but one patient showed a good response to treatment with amiodarone. The prognosis in general is poor and the disease is usually fatal.Visit the Orphanet disease page for more resources. Last updated: 5/22/2008