History
Because protein digestion is expected to be largely dependent on enteropeptidase activity, enterokinase deficiency causes protein malabsorption during early infancy. However, for unknown reasons, protein digestion improves with time and can be adequate in the adult. In adulthood, patients have normal body weight and no GI symptoms, even in the absence of pancreatic enzyme supplements.
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Almost all patients present at birth with diarrhea and failure to thrive.
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All patients exhibit hypoproteinemia.
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Vomiting has been reported in approximately 50% of patients.
Physical
See the list below:
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Affected children present with a malabsorption syndrome characterized by muscle wasting, failure to thrive, and hypoproteinemia (eg, kwashiorkor). This malabsorption syndrome is generalized during the disease's early phase and includes steatorrhea, but these changes are probably secondary to protein malnutrition.
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Generalized edema occurs in one half of affected patients.
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Severe anemia, which is common, is presumably secondary to protein malabsorption and vitamin E deficiency.
Causes
Identification of enterokinase deficiency in 2 pairs of siblings has suggested that the condition is inherited. In these families, Holzinger et al identified mutations in the serine protease-7 gene (PRSS7 gene), which encodes proenterokinase. Therefore, enterokinase deficiency can be considered to be caused by a mutation in the PRSS7 gene. [6]
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Position of mutations (red arrows), in relation to proenteropeptidase exon organization, domains, and amino acid residues forming the active site of the serine protease domain (H825, D876, and S971 [blue arrows]). All 4 mutations identified are null mutations that predict the absence of a correctly formed active site. The previously described modular structure of proenteropeptidease domains, based on primary-structure comparison, correlates with exon boundaries. SA = signal/anchor sequence; LDLR = LDL receptorlike domain; Muc = Mucin-domain; Meprin = Meprinlike domain; C1r/s = Complement component C1rlike domain; MSCR = Macrophage scavenger receptorlike domain. Adapted from American Journal of Human Genetics.
