Pharmacology
Systemic absorption of the globular tetradecapeptide is minimal.Linaclotide, like the endogenous guanylin and uroguanylin it mimics, is an agonist that activates the cell surface receptor of guanylate cyclase 2C (GC-C). The medication binds to the surface of the intestinal epithelial cells. Linaclotide is minimally absorbed and it is undetectable in the systemic circulation at therapeutic doses. Activation of GC-C increases cyclic guanosine monophosphate (cGMP). Elevated cGMP stimulates secretion of chloride and bicarbonate and water into the intestinal lumen, mainly by way of cystic fibrosis transmembrane conductance regulator (CFTR) ion channel activation. This results in increased intestinal fluid and accelerated transit. By elevating cGMP, linaclotide is also considered to reduce activation of colonic sensory neurons, reducing pain; and activates colonic motor neurons, which increases smooth muscle contraction and thus promotes bowel movements. Chemistry
Linaclotide is a hybrid peptide design of the E.coli heat-stable enterotoxin (STa) and the endogenous peptide hormones endogenous guanylin and uroguanylin.
Imaging findings
The most consistent finding are widespread calcifications, which involve
the white matter of the cerebrum mostly adjacent to the junction with the grey matter, the thalami, the basal ganglia and the brainstem. The white matter of the cerebellum and the dentate nuclei are less often involved. However, the brain may appear normal in the neonatal period. The calcifications are visible both with computed tomography and with magnetic resonance imaging. Magnetic resonance imaging shows additionally diffuse or patchy white matter changes, especially in the periventricular region, the thalami and the internal capsule. Cerebellar and brainstem lesions are less common. Imaging also uncovers parenchymal cysts situated mainly in the thalamic region and more rarely in the brainstem, the parietal lobe and the frontal lobe. The long bones may be osteopenic and various skeletal changes are found in several patients, such as metaphyseal sclerosis and mild flaring, which is most pronounced in the femur and  tibia. Laboratory findings
The cerebrospinal fluid and blood tests are typically normal, except for anemia and thrombocytopenia in some children. Screening
Because of the rarity of the syndrome, it is not routinely screened before birth. Prenatal diagnosis is possible in families in which a prior child has been diagnosed, because the responsible gene CTC1is known. Management
Seizures are managed with anticonvulsive medications. Laser coagulation or cryoablation (freezing) of the retina can be used to destroy the abnormal blood vessels. Retinal detachment is repaired with a scleral buckle or with vitrectomy.