Letters to the Editor

Congenital disorders of glycosylation IIa cause growth retardation, mental retardation, and facial dysmorphism EDITOR—Congenital disorders of glycosylation (CDG) are a heterogeneous group of autosomal recessive multisys-temic conditions causing severe central nervous system and multivisceral disorders resulting from impairment of the glycosylation pathway.1–3 Two disease causing mechanisms have been identified so far. CDG I is caused by a defect in the assembly of the dolicholpyrophosphate oligosaccharide precursor of N-glycans and its transfer to the peptide chain, while CDG II results from a defect in the processing of N-glycans.3 CDG I and II have distinct patterns of abnormal glycosylation depending on the reduction of the glycan chain number or its structure. CDG I, the most fre-quent form, is the result of diVerent enzyme deficiencies: phosphomannomutase (CDG Ia), phosphomannose iso-merase (CDG Ib), and glucosyltransferase (CDG Ic).3–6 CDG IIa is characterised by a defect in N-acetylglucosaminyltransferase II and only two cases have been reported previously.7–11 Here, we report a new case of CDG IIa sharing a number of clinical features with the two previously reported cases and emphasising the clinical dif-ferences from CDG I. A boy was born at term to unrelated, healthy parents after a normal pregnancy and delivery, birth weight 3050 g, length 48 cm, and OFC 35 cm. At 3 months of age, hypo-tonia, feeding diYculties, and diarrhoea were noted. A milk protein intolerance was suspected and he was put on a milk free formula until the age of 4 years. He was first referred to our genetic unit at 8 years of age because of mental retardation and facial dysmorphism. On examination, he had severe mental retardation with no speech and an unstable gait. Dysmorphic features included fine hair, large ears, a beaked nose with hypoplastic nasal alae, a long philtrum, thin vermilion border of the upper lip, everted lower lip, large teeth, and gum hypertrophy (fig 1). Long standing feeding diYculties and diarrhoea had resulted in severe growth retardation (height 109.9 cm (−3 SD), weight 20 kg (−2.5 SD), OFC 50.5 cm (−2 SD)). Chromosome analysis was normal and no diagnosis was made at that time. At 11 years of age, dysmorphic features, severe mental retardation, diarrhoea, and growth retarda-tion were still present (height 120.8 cm (−4 SD), weight 2