Key Clinical and Laboratory Features

  • Common clinical features: Early-onset enteropathy, eczema, and interstitial lung disease. Significant growth delay, dwarfism with normal growth hormone but low IGF-1. Recurrent, severe infections including bacterial sinopulmonary infections, Pneumocystis jirovecii pneumonia, and severe/chronic viral infections (CMV, VZV, HSV, etc.).
  • Other clinical features: Facial dysmorphisms (prominent forehead, saddle nose), high-pitched voice.
  • Physical exam: Dwarfism, growth abnoramalities. Facial dysmorphism. Abnormalities of pulmonary exam consistent with interstitial lung disease, eczema.
  • Common laboratory features: T-cell and NK-cell lymphopenia. Normal serum growth hormone level but low Insulin-like Growth Factor-1 (IGF-1) level. Serum immunoglobulin levels may be decreased.

Testing Approach

  Test Comments
Gene STAT5B Gene Sequencing   The gold standard for confirming a diagnosis of STAT5B deficiency in a patient with suggestive symptoms.
Protein and Function N/A There are currently no available clinical tests to evaluate STAT5B protein expression or function because of a paucity of reagents to reliably differentiate STAT5B from STAT5A.
  • Complete blood count with differential: Lymphopenia may be present.
  • Lymphocyte subset analysis: T-cell and NK-cell lymphopenia.
  • Lymphocyte proliferation to mitogens: Patient T cells often do not proliferate well to mitogens.
  • Quantitative immunoglobulin levels: gG and IgA may be low.
  • Specific antibody titers: Typically low.
  • Chest X-ray, chest CT, and pulmonary function tests: Consistent with interstitial lung disease.