Signal Transducer and Activator of Transcription 5 (STAT5B) Deficiency

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.

	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.
OTHER		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.