Background: Mucolipidosis-type-II (ML-II) is rare progressive neurodegenerative lysosomal storage disease (LSD). The characteristic clinical features become evident within the first year of life. Case presentation and results: This 6-month-old girl was born at term by Caesarean-section. She had blueberry muffin rash with multiple nonblanching purplish lesions and 2 cm palpable liver. Laboratory investigations revealed neutropenia, marked thrombocytopenia, unconjugated and conjugated hyperbilirubinemia and moderately elevated lactate dehydrogenase at age 4 days. Skeletal radiographs showed diffuse periostitis of all long bones suggesting congenital infections. However all serological investigations were negative. There were large, very prominent cytoplasmic vacuoles within the lymphocytes on peripheral smear, which led us to investigate for LSD at age 5 days. Serum total hexosaminidase, hexosaminidase A and alpha-N-acetylglucosaminidase enzyme activities were markedly elevated suggesting ML-II at age 10 days. She had known homozygous disease causing mutation in the GNPTAB gene (c.3503_3504delTC) confirming the diagnosis of ML-II. Conclusion: This is the first patient with ML-II presented with blueberry muffin rash. Peripheral blood film examination is a simple, cheap and readily available screening test to diagnose patients with LSD in the neonatal period. As bone marrow transplantation is widely used treatment option for the most LSD, early diagnosis is crucial.