# Case Report: A novel KRT74 variant in an eight-year-old boy with alopecia totalis successfully treated with baricitinib

## TL;DR

An 8-year-old boy with alopecia totalis and a KRT74 gene variant showed significant hair regrowth after treatment with baricitinib.

## Contribution

A novel KRT74 variant is linked to alopecia areata, and JAK inhibitors may be effective in genetically predisposed cases.

## Key findings

- The patient showed significant hair regrowth within one month of baricitinib treatment.
- Immunofluorescence revealed increased JAK1-STAT1 phosphorylation and CD4+ T cell infiltration in the scalp.
- The KRT74 variant was present in family members without alopecia, suggesting a genetic predisposition.

## Abstract

Alopecia areata is an autoimmune condition characterized by non-scarring hair loss, with genetic factors playing a significant role in disease susceptibility. We report the case of an 8-year-old boy with alopecia totalis harboring a heterozygous KRT74 variant. While his mother and brother share this variant, they do not exhibit alopecia. Immunofluorescence analysis revealed increased phosphorylation of the JAK1-STAT1 pathway and elevated T cell infiltration, predominantly CD4+ T helper cells, in the proband’s scalp. The patient responded favorably to baricitinib treatment (2 mg/day), showing significant hair regrowth within 1 month and continued improvement over 8 months. This case suggests that KRT74 variants may contribute to immune dysregulation in alopecia areata, highlighting the potential role of JAK inhibitors in genetically predisposed alopecia cases.