Initial or mild symptoms typically develop within 2 hours and include tachycardia, drowsiness, a dry mouth, nausea and vomiting, urinary retention, confusion, agitation, and headache. More severe complications include hypotension, cardiac rhythm disturbances, hallucinations, and seizures. Electrocardiogram (ECG) abnormalities are frequent and a wide variety of cardiac dysrhythmias can occur, the most common being sinus tachycardia and intraventricular conduction delay resulting in prolongation of the QRS complex and the PR/QT intervals. Seizures, cardiac dysrhythmias, and apnea are the most important life-threatening complications. Cause
Tricyclics have a narrow therapeutic index, i.e., the therapeutic dose is close to the toxic dose. Factors that increase the risk of toxicity include advancing age, cardiac status, and concomitant use of other drugs. However, serum drug levels are not useful for evaluating risk of arrhythmia or seizure in tricyclic overdose. Pathophysiology
Most of the toxic effects of TCAs are caused by four major pharmacological effects. TCAs have anticholinergic effects, cause excessive blockade of norepinephrine reuptake at the preganglionic synapse, direct alpha adrenergic blockade, and importantly they block sodium membrane channels with slowing of membrane depolarization, thus having quinidine-like effects on the myocardium. Diagnosis
A specific blood test to verify toxicity is not typically available. An electrocardiogram (ECG) should be included in the assessment when there is concern of an overdose. Treatment
People with symptoms are usually monitored in an intensive care unit for a minimum of 12 hours, with close attention paid to maintenance of the airways, along with monitoring of blood pressure, arterial pH, and continuous ECG monitoring.
Osteochondromas
Osteochondromas are benign tumors located on the surface of bone near growth plates. These tumors also often in the hands and feet, primarily affecting the digits of fingers and toes. These tumors tend to subside after 10-20 years of life. These tumors can become painful if they pressure sensitive tissue or nerves. Metachondromatosis is differentiated from hereditary multiple osteochondromas by the location of the location of Osteochondromas tumors as well as the lack of bone-shortening. Abnormality of epiphysis morphology
The epiphysis is the rounded end part of bone. The structure of the epiphysis can be abnormal in metachondromatosis. Abnormality of the metaphysis
The metaphysis is wide portion of a long bone, and also has abnormal structure in the disease. Avascular necrosis
Avascular necrosis is the death of bone due to a decreased blood supply. Bone pain
People with metachondromatosis often experience bone pain due to abnormal bone shapes. Cranial nerve paralysis
Cranial nerve paralysis can affect the functions associated with the cranial nerve. Genetics
Metachondromatosis is inherited in an autosomal dominant manner, needing only one copy of the defective gene to cause the disorder. The cause of the disorder has been linked to an 11 base pair deletion in exon four of the PTPN11 gene  (12q24.13). This deletion causes a frameshift, resulting in a nonsense mutation with a premature stop codon. This causes severe truncation and loss of function in the gene’s protein product, tyrosine phosphatase SHP-2.