Introduction JAK/STAT pathways dysregulations can lead to a broad spectrum of immune disturbances varying from immune deficiency when a loss of function is found to auto immunity in the case of gain of function (GOF) of the pathway, with gain of function mutations described in STAT 1, 3 and 6.
Case We present the case of an eleven-year-old male patient who was referred to the National Institute of Pediatrics due to the diagnosis of alopecia . During his initial evaluation short stature was found under -3 SD (standard deviation) and IGF1 and IGFBP3 deficiency was documented. He was referred to the allergy department because of allergic rhinitis clinical symptoms, where normal IgE levels and eosinophilia of 3100 cel/mm3 were found. Chronic cough, arthralgias, and skin lesions in elbows and knees with skin biopsy suggestive of calcinosis cutis were added to the clinical symptoms. Immunological tests showed hypergammaglolbulinemia with low complement levels and positive anti-nuclear antibodies. Exome sequencing revealed a novel mutation in STAT5B:C.1924A>C (p. Asn642His), Because of the patient’s persistent alopecia in the head and eyebrows along with the STAT5B mutation finding, treatment with ruxolitinib and hydroxychloroquine were started which resulted in hair growth in the head and eyebrows with a decrease in the calcinosis cutis lesions and lower eosinophil levels after a three-month treatment. Discussion This patient shows multiple signs and symptoms associated with self-reactivity along with a mutation in STAT5B. A scarce number of pediatric patients with GOF of STAT5B have been reported, most of them associated with lymphoproliferative malignances. The combined treatment of ruxolitinib and hydroxychloroquine has improved the patient’s clinical course, including the calcinosis cutis and promoting hair growth. Sanger test is still pending to assess or discard STAT5B GOF.