Four female Mexican-American infants, two siblings, had widespread deposit of hyaline material in skin, gastrointestinal tract, adrenals, urinary bladder, ovaries, skeletal muscles, thymus, parathyroids, and other loci. Clinical features included thickness and focal nodularity of skin, relatively short limbs and neck, gum hypertrophy, hypotonia and reduced movement, joint contractures, osteoporosis, growth failure, diarrhea, and recurrent infections. Clinical onset was in the first week, and all 4 patients died by age 20 months. Infantile systemic hyalinosis appears to be a specific, presumably autosomal recessive, genetic disease, differing from the disorder called systemic hyalinosis, juvenile hyaline fibromatosis, or Puretic syndrome. The biochemical defect and the pathogenetic mechanisms responsible for the pathologic and clinical features of this condition remain to be established.