Table 2 Clinical observations in the atypical hypotonia–cystinuria syndrome (HCS) patients

	Patient 1	Patient 2
Age	17 years	10.5 years
Sex	Male	Female
Poor sucking, nasogastric tube feeding as neonates	+	+
Sitting alone	13 months	10 months
Walking alone	3.5 years	17 months
Neonatal hypotonia	+	+
Facial dysmorphy	+	+
Psychomotor retardation	Moderate	Moderate
Growth retardation	+	+
GH stimulation (glucagon)	Not performed	Normal
Hyperphagia	−	−
Cystinuria type I	+1 calculus observed	+1 calculus observed
Lithiasis	+	+
Nerve conduction velocities	Not performed	Normal
Electromyography	Normal (at 5 months)	Normal (at 5 months)
	Chronic denervation (17 years)	Chronic denervation (9 years)
Muscle biopsy	Disproportionate fibre size
	Hypotrophy of type I fibres
	Nuclear inclusions	Nuclear inclusions
	Hypotrophy of type II fibres	Hypotrophy of type II fibres
	Respiratory chain not studied	Complex IV deficiency
Brain MRI	Normal	Specific abnormalities