microcephaly with or without short stature microcephaly 6 with or without short stature https://github.com/monarch-initiative/mondo/issues/4686 https://github.com/monarch-initiative/mondo/issues/6199 MONDO:0700054 GARD:0026336 Disorder of fetal brain growth; individuals have small brains and almost always have mental retardation, although rare individuals with mild microcephaly (-3 SD) and normal intelligence have been reported. Clinical features include the features of ‘microcephaly 6, primary, autosomal recessive’ and 'Seckel syndrome', and may include short stature or mild seizures. Primary microcephaly refers to the clinical finding of a head circumference more than than 3 standard deviations (SD) below the age- and sex-related mean, present at birth. Primary microcephaly is a static developmental anomaly, distinguished from secondary microcephaly, which refers to a progressive neurodegenerative condition. Microcephaly is a disorder of fetal brain growth; individuals with microcephaly have small brains and almost always have mental retardation, although rare individuals with mild microcephaly (-3 SD) and normal intelligence have been reported. Additional clinical features may include short stature or mild seizures. These clinical features include Seckel syndrome, a rare autosomal recessive disorder characterized by intrauterine growth retardation, dwarfism, microcephaly with mental retardation, and a characteristic 'bird-headed' facial appearance (Shanske et al., PMID: 9128935). MCPH is associated with a simplification of the cerebral cortical gyral pattern and a slight reduction in the volume of the white matter, consistent with the small size of the brain, but the architecture of the brain in general is normal, with no evidence of a neuronal migration defect (Woods et al., PMID: 15806441). Seckel syndrome 4 and autosomal recessive primary microcephaly 6 are currently lumped together into one disease entity per the criteria outlined by the ClinGen Lumping and Splitting Working Group, while more published literature detailing Seckel syndrome 4 may support two split disease entities in the future.