Clinical Characteristics
Ocular Features
The major ocular features involve the periocular structures. These result in the typical facial dysmorphism and include hypertelorism, blepharoptosis, blepharophimosis, and highly arched eyebrows. Ptosis, unilateral or bilateral, can be present.
One patient was reported to have unilateral aniridia and a corneal leucoma. Tear duct atresia was reported in another individual.
Systemic Features
Systemic features are highly variable in their presence and severity. Facial clefting, growth deficiency, cognitive impairment, and hearing loss are present about half the time in some combination while craniosynostosis, urogenital anomalies, and radioulnar synostosis are seen in about a third of individuals. More rare features include cardiac defects and abdominal midline defects (omphalocele and diastasis recti).
Genetics
Inheritance
This condition (3MC) is now postulated to include at least 3 disorders (Malpuech-Michels-Mingarelli-Carnevale syndromes) and considered here as a single autosomal recessive disease complex with overlapping clinical features that requires genotyping for diagnostic separation. These are: 3MC1 syndrome (257920) resulting from homozygous mutations in the MASP1 gene (3q27.3), 3MC2 syndrome (265050) caused by mutations in the COLEC11 gene (2p25.3) and 3MC3 (248340) with mutations in the COLEC10 gene (8q24.12).
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.