In the case of mediastinal lymphadenopathy, the enlarged lymph node causes compression of the lymphatic channels and thoracic duct. This impedes the centripetal drainage of the flow of lymph from the edges of the lung parenchyma and pleural surfaces. This causes the chyle to ooze extensively into the pleural cavity, leading to a chylothorax. In the case of yellow nail syndrome, or lymphedema, chylothorax is caused by hypoplasia or dilation of the lymph vessels. In rare cases, like in hepatic chylothorax, chylous ascites crosses the diaphragm into the pleural cavity. In idiopathic cases like genetic disorders, the mechanism is not known. Up to three liters of chyle can easily drain into the pleural space daily. Diagnosis
Chest X-rays can detect a chylothorax. It appears as a dense, homogeneous area that obscures the costophrenic and cardiophrenic angles. Ultrasounds can also detect a chylothorax, which appears as an echoic region that is isodense with no septation or loculation. However, neither a normal chest x-ray nor an ultrasound can differentiate a chylothorax from any other type of pleural effusion. The cisterna chyli can be found in a thoracic MRI, making it possible to confirm chylothorax. However, MRI is not the ideal method to scan the thorax, and so it is rarely used. Another diagnostic technique is conventional lymphangiography. It is rarely used since there are equally sensitive yet less invasive techniques available to identify a chylothorax. Lymphangiography procedures use the contrast dye agent lipiodol, which is injected into the lymphatic vessels.
Idiopathic unilateral circumscribed hyperhidrosis
Reported association with:
Blue rubber bleb nevus
Glomus tumor
POEMS syndrome
Burning feet syndrome (Gopalans)
Trench foot
Causalgia
Pachydermoperiostosis
Pretibial myxedema
Gustatory sweating associated with:
Encephalitis
Syringomyelia
Diabetic neuropathies
Herpes zoster (shingles)
Parotitis
Parotid abscesses
Thoracic sympathectomy
Auriculotemporal or Freys syndrome
Miscellaneous
Lacrimal sweating (due to postganglionic sympathetic deficit, often seen in Raeders syndrome)
Harlequin syndrome
Emotional hyperhidrosis

Cancer
A variety of cancers have been associated with the development of secondary hyperhidrosis including lymphoma, pheochromocytoma, carcinoid tumors (resulting in carcinoid syndrome), and tumors within the thoracic cavity. Endocrine
Certain endocrine conditions are also known to cause secondary hyperhidrosis including diabetes mellitus (especially when blood sugars are low), acromegaly, hyperpituitarism, pheochromocytoma (tumor of the adrenal glands, present in 71% of patients) and various forms of thyroid disease. Medications
Use of selective serotonin reuptake inhibitors (e.g., sertraline) is a common cause of medication-induced secondary hyperhidrosis. Other medications associated with secondary hyperhidrosis include tricyclic antidepressants, stimulants, opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), glyburide, insulin,  anxiolytic agents, adrenergic agonists, and cholinergic agonists. Miscellaneous
In people with a history of spinal cord injuries
Autonomic dysreflexia
Orthostatic hypotension
Posttraumatic syringomyelia
Associated with peripheral neuropathies
Familial dysautonomia (Riley-Day syndrome)
Congenital autonomic dysfunction with universal pain loss
Exposure to cold, notably associated with cold-induced sweating syndrome
Associated with probable brain lesions
Episodic with hypothermia (Hines and Bannick syndrome)
Episodic without hypothermia
Olfactory
Associated with systemic medical problems
Parkinsons disease
Fibromyalgia
Congestive heart failure
Anxiety
Obesity
Menopausal state
Night sweats
Compensatory
Infantile acrodynia induced by chronic low-dose mercury exposure, leading to elevated catecholamine accumulation and resulting in a clinical picture resembling pheochromocytoma. Febrile diseases
Vigorous exercise
A hot, humid environment

Diagnosis
Symmetry of excessive sweating in hyperhidrosis is most consistent with primary hyperhidrosis. To diagnose this condition, a dermatologist gives the patient a physical exam.