There are myriad ways to mine the data from the review of 100 cases of PRP by Ross et al, however, one key finding will change the way I will assess these patients – 20% were hypothyroid! (1)
There have only been a few reports in the medical literature linking hypothyroidism to PRP. Franzotti et al reported the case of a 30-year-old man with PRP who demonstrated rapid improvement within a month of thyroid hormone replacement (2). A 24-year-old man with classical PRP had loss of eyebrow hair. The authors suspected possible hypothyroidism, which was confirmed by an elevated TSH. He also responded dramatically within a month to the administration of thyroid hormone (3). A 4 year-old with erythrodermic PRP and hypothyroidism resolved after 3 months of thyroid hormone replacement (4).
There has always been a presumption that aberrations in vitamin A metabolism may play a role in PRP. According to Franziotti et al (2):
Hypothyroidism is directly linked to vitamin A metabolism alteration. The thyroid hormone is fundamental to the conversion of ingested carotenes to vitamin A. The hypothyroidism patients present almost total blockage of this conversion and only a small amount of carotenoids, not converted to vitamin A, are absorbed by humans.
Chances are that you will be checking labs (CBC, LFTs, lipid profile, HIV, quantiferon TB gold) should you decide to treat PRP with systemic agents (acetretin, methotrexate, TNF inhibitors). Add a TSH to the panel – there is a possibility that it will guide you to all the treatment you need – thyroid hormone.
- Ross NA, et al. Epidemiologic, clinicopathologic, diagnostic, and management challenges of pityriasis rubra pilaris: A case series of 100 patients. JAMA Dermatology 2016; 152: 670-5.
- Franzotti AM, et al. Pityriasis rubar pilar and hypothyroidism. An Bras Dermatol 2014; 89: 497-500.
- Pityriasis rubra pilaris and hypothyroidism. Efficacy of thyroid hormone replacement therapy in skin recovery. Br J Dermatol 2007; 156: 606-7.
- Tunnessen WW Jr, et al. Hypothyroidism and pityriasis rubra pilaris. Response to thyroid hormone. J Pediatr 1976; 88: 456-8.