Table 2.

Select non-dysostosis multiplex skeletal disorders which may be confused with MPS IVA

Category	Differential diagnosis	Distinguishing clinical/radiographic features	References
Spondyloepiphyseal dysplasia (SED)	SED congenita	Symptoms present from birth	(Fraser et al 1969)
	Dyggve-Melchior-Clausen syndrome (pseudo-Morquio syndrome type 1)	Intellectual disability and lace-like appearance of the iliac crests in radiographs	(Nakamura et al 1997; Nishimura et al 2010)
	Smith-McCort syndrome	Lace-like appearance of the iliac crests in radiographs	(Nakamura et al 1997; Cohn et al 2003; Nishimura et al 2010)
	SED, Maroteaux type (pseudo-Morquio syndrome type 2)	Smooth and uniform platyspondylysis, no anterior beaking of the vertebrae, upper femoral metaphyses are enlarged and short	(Doman et al 1990; Megarbane et al 2004; Nishimura et al 2010)
	X-linked SED tarda	Coxa vara, disproportionately long arms relative to height, superior and inferior humping of vertebral bodies	(Whyte et al 1999)
	Autosomal recessive SED tarda	Intellectual disability	(Kohn et al 1987b)
Spondylometaphyseal dysplasia (SMD)	SMD, Kozlowski type	Overfaced vertebral pedicles, irregular proximal femoral growth plates	(Krakow et al 2009)
Brachyolmia	Types 1, 2, and 3	Lack of long bone involvement	(Shohat et al 1989)
Other	Legg-Calve-Perthes disease	Involvement limited to hips	(Miyamoto et al 2007)