Hypochondroplasia (HCH) is a developmental disorder caused by an autosomal dominant genetic defect in the fibroblast growth factor receptor 3 gene (FGFR3) that results in a disproportionately short stature, micromelia and a head that appears large in comparison with the underdeveloped portions of the body. It is classified as short-limbed dwarfism. Signs and symptoms
Individuals affected by this disorder appear normal at birth. As the infant grows, however, their arms and legs do not develop properly, and their body becomes thicker and shorter than normal. The following are characteristics consistent with this condition:
Brachydactyly
Short stature
Micromelia
Skeletal dysplasia
Abnormality of femur

Cause
Hypochondroplasia is transmitted as an autosomal dominant trait affecting the FGFR3 gene on chromosome 4p16.3. There is currently no cure for this condition. Pathophysiology
This disorder results from mutations in the proximal tyrosine kinase domain of the FGFR3 gene. This gene plays an important role in embryonic development, playing a part in regulating activities such as cell division, migration and differentiation.Hypochondroplasia can result from p. Lys650Asn as well. In FGFR3, some 20 different mutations have been associated to hypochondroplasia, and it seems to have a role in skeletal dysplasia. Diagnosis
The diagnosis of this condition can be done via X-rays (with lack of normal distance L1 to L5), and additionally genetic testing is available to ascertain hypochondroplasia. However, the physical characteristics are one of the most important in determining the condition. Treatment
Treatment of hypochondroplasia usually takes the form of orthopedic surgery and physical therapy. Genetic counseling is advised for individuals and their families.
Based on these additional studies, the FDA granted in 2016 full approval and updated the label to include patients with chronic phase, accelerated phase, or blast phase chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia for whom no other tyrosine kinase inhibitor therapy is indicated. Approval was also granted for T315I-positive and T315I-positive Philadelphia chromosome positive acute lymphoblastic leukemia. Adverse effects
The United States Food and Drug Administration issued a partial clinical hold on new trial enrollment for ponatinib on October 9, 2013, due to an increased number of blood clots observed in patients taking the drug. The EPIC trial was later canceled on October 18. Subsequent studies of 449 patients treated during 4 years with ponatinib for chronic phase chronic myelogenous leukemia found the following adverse reactions. 150 Patients experienced cardiac vascular (21% of patients), peripheral vascular (12%), and cerebrovascular (9%) arterial occlusive events. Venous thromboembolic events occurred in 6% of patients. The most common all-grade adverse events included hypertension (69%), rash (63%), abdominal pain (48%), fatigue (47%), headache (43%), arterial ischemia (42%), dry skin (42%), constipation (41%), arthralgia (32%), nausea (28%), pyrexia (26%), peripheral neuropathy (24%), myalgia (24%), pain in extremity (23%), back pain (21%), and diarrhea (20%). In addition, there have been reported cases of the posterior reversible encephalopathy syndrome. Recently, an analogue of ponatinib was developed that retained anti-tumor efficacy but had reduced cardiovascular toxicity in experimental models.