Pontocerebellar hypoplasia (PCH) is a heterogeneous group of rare neurodegenerative disorders caused by genetic mutations and characterised by impaired development of various parts of the brain (cerebellum, brainstem).
Pontocerebellar hypoplasia is classified as follows:
|Type||OMIM||Gene||Locus||Distinctive features||Alternate names|
|1A (PCH1A)||607596||VRK1||14q32||Anterior horn cell degeneration||Spinal muscular atrophy with pontocerebellar hypoplasia (SMA-PCH)|
|1B (PCH1B)||614678||EXOSC3||9p13.2||Hypotonia, respiratory insufficiency, muscle atrophy|
|2A (PCH2A)||277470||TSEN54||17q25.1||Dyskinetic movements, seizures (frequently)||Volendam neurodegenerative disease|
|2D (PCH2D)||613811||SEPSECS||4p15.2||Progressive cerebello-cerebral atrophy (PCCA)|
|3 (PCH3)||608027||CLAM||7q11–q21||Seizures, short stature, optic atrophy||CLAM-PCH, cerebellar atrophy with progressive microcephaly|
|4 (PCH4)||225753||TSEN54||17q25.1||Severe prenatal form of PCH2 with polyhydramnios, contractures, myoclonus, apneic episodes and early death following birth|
|5 (PCH5)||610204||unknown||unknown||Severe prenatal form, described in one family||Olivopontocerebellar hypoplasia (OPCH)|
|6 (PCH6)||611523||RARS2||6q15||Severe encephalopathy in the newborn with hypotonia, and inconstantly: intractable seizures, edema, increased lactate blood levels, mitochondrial respiratory chain defects|
|7 (PCH7)||—||unknown||unknown||Hypotonia, apneic episodes, seizures, vanishing testis|
- Facial features (dysmorphism) of patients with one form of pontocerebellar hypoplasia due to mutations in the CASK gene. A and B: patient at 1 year (A) and 4 years (B). C: patient, 18 months. D: patient, 13 years. E: patient, 13 years. F: patient, 12 years. Note minor facial dysmorphism: round face, small chin, well-drawn eyebrows in the younger patients; longer face, high and large nasal bridge, long nose, protuding maxilla, in the older patients.
- Magnetic resonance imaging (MRI) examples of patients with pontocerebellar hypoplasia with CASK mutations. A. Sagittal images showing different degrees of hypoplasia (incomplete formation) of the pons and vermis (parts of the brain). Numbers represent different patients. Figure 9a shows an MRI of a patient at age 4 months and figure 9b shows the same patient at age 11 years. There is no progression of the lesions between successive MRI in patient 9. Note that in all patients, the pons is very small but has a relative sparing of its buldging, mainly in its superior part. Hypoplasia predominates at the lower part of the pons. Vermis hypoplasia is very variable, severe in patient 13, very slight in patient 10-11-12 and also predominates at the inferior part. B. Coronal images showing varying degrees of cerebellar hemispheric (one of two halves of a part of the brain) hypoplasia. Hemispheres are frequently asymmetric. Note that the vermis does not protrude from the hemispheres indicating similar involvement of the vermis and the hemispheres. This pattern is different from that of PCH2 in which the vermis is relatively spared leading to the classic image of a "dragonfly", the protruding vermis being the body of the dragonfly and the hemispheres, the wings.
- Anderson, C.; Davies, J. H.; Lamont, L.; Foulds, N. (2011). "Early pontocerebellar hypoplasia with vanishing testes: A new syndrome?". American Journal of Medical Genetics Part A 155 (4): 667. doi:10.1002/ajmg.a.33897.
- Namavar, Y.; Barth, P. G.; Poll-The, B.; Baas, F. (2011). "Classification, diagnosis and potential mechanisms in Pontocerebellar Hypoplasia". Orphanet Journal of Rare Diseases 6: 50. doi:10.1186/1750-1172-6-50. PMC 3159098. PMID 21749694.