I-cell disease (Mucolipidosis II) is one of the lysosomal storage diseases which presents in the neonatal period, and within six months will phenotypically resemble the severe forms of the group of disorders called the "mucopolysaccharidoses" but without mucopolysacchariduria. In Mucolipidosis II, fibrocytes exhibit "abnormal lysosomes". Activities of several lysosomal enzymes are low in fibroblast cultures but high in mucolipidosis II serum. We present a patient with I-cell disease diagnosed on the basis of clinical, radiological and biochemical features. The mother of this child was pregnant and the fetus was also found to be affected.