MedGen

Achondroplasia is the most common cause of disproportionate short stature. Affected individuals have rhizomelic shortening of the limbs, macrocephaly, and characteristic facial features with frontal bossing and midface retrusion. In infancy, hypotonia is typical, and acquisition of developmental motor milestones is often both aberrant in pattern and delayed. Intelligence and life span are usually near normal, although craniocervical junction compression increases the risk of death in infancy. Additional complications include obstructive sleep apnea, middle ear dysfunction, kyphosis, and spinal stenosis. [from GeneReviews]

SADDAN dysplasia (severe achondroplasia with developmental delay and acanthosis nigricans) is a very rare skeletal dysplasia characterized by the constellation of these features. Radiology reveals 'ram's horn' shaped clavicles and reverse bowing of lower limbs. Approximately half of patients die before the fourth week of life secondary to respiratory failure (summary by Zankl et al., 2008). [from OMIM]

An extremely rare type of severe combined immunodeficiency syndrome (SCID) characterized by the classical signs of T-B- SCID (severe and recurrent infections, diarrhea, failure to thrive, absence of T and B lymphocytes) associated with skeletal anomalies like short stature, bowing of the long bones and metaphyseal abnormalities of variable degree of severity. [from SNOMEDCT_US]