A Case of Achondrogenesis Type 2/Hypochondrogenesis Due to a De Novo Mutation in the COL2A1 Gene

Achondrogenesis type 2/hypochondrogenesis is a rare cause of micromelic dwarfism in the neonatal period. Severe short stature, narrow chest, increased lordosis, protuberant abdomen, and characteristic facies are the typical clinical findings. A 13-month-old boy was referred to our clinic for severe short stature and dysmorphic features. He was born at term with a normal birth weight and length. His past medical history was unremarkable. Parents were not related. He had a 7-year-old healthy sister and there was no individual with similar medical condition in the three-generation pedigree. On physical examination, his weight was 7.1 kg [-1.32 standard deviation score (SDS)], length was 63 cm (-5.6 SDS), and head circumference was 49.2 cm (1.84 SDS). He had relative macrocephaly and rhizomelic short stature with atypical facies (frontal bossing, flat nasal bridge, and high-arched palate), narrow chest, increased lumbar lordosis, prominent heels, and overriding toes. His testicles were 1 mL in scrotum and pubic hair was Tanner stage 1. Blood biochemistry revealed normal findings. Radiological investigations showed inadequate ossification and disorganisation in vertebra, sacrum, and pubic bones suggesting achondrogenesis type 2. Due to his severe disproportionate short stature and abnormal radiological findings, a molecular analysis of COL2A1 gene was performed and a de novo mutation causing achondrogenesis type 2/hypochondrogenesis was identified (King Faisal Specialist Hospital and Research Center- Developmental Genetics Unit).