To the Editor:
A 52-year-old man who was otherwise healthy and a long-distance runner presented with the sudden onset of diminished sweating on the left side of the body of 6 weeks’ duration. While training for a marathon, he reported that he perspired only on the right side of the body during runs of 12 to 15 miles; he observed a lack of sweating on the left side of the face, left side of the trunk, left arm, and left leg. This absence of sweating was accompanied by intense flushing on the right side of the face and trunk.
The patient did not take any medications. He reported no history of trauma and exhibited no neurologic deficits. A chest radiograph was negative. Thyroid function testing and a comprehensive metabolic panel were normal. Contrast-enhanced computed tomography of the chest and abdomen revealed a 4.3-cm soft-tissue mass in the left superior mediastinum that was superior to the aortic arch, posterior to the left subclavian artery in proximity to the sympathetic chain, and lateral to the trachea. The patient was diagnosed with Harlequin syndrome (HS).
Open thoracotomy was performed to remove the lesion. Analysis of the mass showed cystic areas, areas of hemorrhage (Figure 1A), and alternating zones of compact Antoni A spindle cells admixed with areas of less orderly Antoni B spindle cells within a hypocellular stroma (Figure 1B). Individual cells were characterized by eosinophilic cytoplasm and tapered nuclei. The mass appeared to be completely encapsulated. No mitotic figures were seen on multiple slides. The cells stained diffusely positive for S-100 proteins. At 6-month follow-up, the patient reported that he did not notice any return of normal sweating on the left side. However, the right-sided flushing had resolved.
FIGURE 1. A, Histopathology of a fully encapsulated schwannoma with cystic areas and hemorrhagic areas (H&E, original magnification ×14). B, Mitotic spindles were absent, and areas of compact Antoni A spindle cells were alternatingly admixed with areas of less orderly Antoni B cells within a hypocellular stroma (H&E, original magnification ×150).
Harlequin syndrome (also called the Harlequin sign) is a rare disorder of the sympathetic nervous system and should not be confused with lethal harlequin-type ichthyosis, an autosomal-recessive congenital disorder in which the affected newborn’s skin is hard and thickened over most of the body.1 Harlequin syndrome usually is characterized by unilateral flushing and sweating that can affect the face, trunk, and extremities.2 Physical stimuli, such as exercising (as in our patient), high body temperature, and the consumption of spicy or pungent food, or an emotional response can unmask or exacerbate symptoms of HS. The syndrome also can present with cluster headache.3 Harlequin syndrome is more common in females (66% of cases).4 Originally, the side of the face marked by increased sweating and flushing was perceived to be the pathologic side; now it is recognized that the anhidrotic side is affected by the causative pathology. The side of the face characterized by flushing might gradually darken as it compensates for lack of thermal regulation on the other side.2,5
Usually, HS is an idiopathic condition associated with localized failure of upper thoracic sympathetic chain ganglia.5 A theory is that HS is part of a spectrum of autoimmune autonomic ganglionopathy.6 Typically, the syndrome is asymptomatic at rest, but testing can reveal an underlying sympathetic lesion.7 Structural lesions have been reported as a cause of the syndrome,6 similar to our patient.
Disrupted thermoregulatory vasodilation in HS is caused by an ipsilateral lesion of the sympathetic vasodilator neurons that innervate the face. Hemifacial anhidrosis also occurs because sudomotor neurons travel within the same pathways as vasodilator neurons.4
Our patient had a posterior mediastinal ancient schwannoma to the left of the subclavian artery, lateral to the trachea, with ipsilateral anhidrosis of the forehead, cheek, chin, and torso. In the medical literature, the forehead, cheek, and chin are described as being affected in HS when the lesion is located under the bifurcation of the carotid artery.3,5 Most of the sudomotor and vasomotor fibers that innervate the face leave the spinal cord through ventral roots T2-T34 (symptomatic areas are described in Figure 2), which correlates with the hypothesis that HS results from a deficit originating in the third thoracic nerve that is caused by a peripheral lesion affecting sympathetic outflow through the third thoracic root.2 The location of our patient’s lesion supports this claim.
FIGURE 2. Affected anatomic areas in Harlequin syndrome with possible lesion sites.