Pontocerebellar hypoplasia type 3 (PCH3), also known as cerebellar atrophy with progressive microcephaly (CLAM) is a rare form of pontocerebellar hypoplasia (see this term) with autosomal recessive transmission characterized neonatally by hypotonia and impaired swallowing and from infancy onward by seizures, optic atrophy and short stature, but none of the clinical findings are specific for PCH3.
To date, PCH3 is reported in only 3 families.
Neonatally, PCH3 is characterized by hypotonia and impaired swallowing. From infancy onwards, the main features of PCH3 include progressive microcephaly with brachycephaly, optic atrophy, seizures during the first year of life, severe developmental delay, truncal hypotonia, with increased limb deep tendon reflexes and signs of spasticity of the limbs. Other characteristics such as facial dysmorphism (low set ears and prominent eyes), short stature and low weight are also reported. None of the clinical findings are specific.
The etiology of PCH3 remains largely elusive. In 2 families, an implication of locus 7q11-21 has been demonstrated. PCH3 is inherited in an autosomal recessive manner.
MRI demonstrates neocortical and pontocerebellar hypoplasia with pons and cerebellum equally affected a small brainstem, prominent sulci and lateral ventricles and decreased cerebral white matter volume. It is recommended to limit the diagnosis of PCH3 to families with PCH and linkage to 7q11-21, until more precise identification of the associated gene becomes possible.
There is no information on life expectancy, but reported PCH3 patients do not appear to regress.
Last update: July 2013