(BMJ)—A 3-year-old girl presented with a 1-month hx of progressive discoloration at the tip of her R index finger. No hx of injury or insect bite; no pain, pruritus, or paresthesia. Parents reported that the girl habitually rubbed her scalp with this finger. Exam: brown patch on tip of R index finger. No discoloration on other fingers, oral mucosa, teeth, or eyes. Finger range of motion normal. Application of 75% ethanol didn’t affect the discoloration. What’s the dx?
Acral nevus
Exogenous staining
Frictional dermatitis
Buerger disease
You are correct. The patient was diagnosed with frictional dermatitis caused by repetitive mechanical stress (habitual scalp rubbing). Frictional dermatitis is mainly diagnosed based on clinical findings. Dermoscopy can help in dx but depends primarily on the skill of the operator. Pinpoint hemorrhagic suffusions and parallel ridge pattern of pigmentation may be observed by dermoscopy. Drug tx isn’t needed for frictional dermatitis; ceasing the causative behavior is sufficient. The lesion had completely resolved 3 months after the patient stopped rubbing her scalp. To ensure cessation of this habit, the parents were asked to distract their daughter when she attempted to rub her scalp. The lesion hadn’t recurred by the 4-month follow-up visit.

BMJ 2022;377:e070336
(BMJ)—A man in his 50s presented with a 2-week hx of a large bruise on his L foot and a 2-month hx of a rash on his bilateral lower limbs. PMHx: HCV treated 3 years earlier; HIV on antiretrovirals; remote hx of alcohol and injection drug use. No trauma/fever/night sweats/weight loss/other bleeding. Exam: poor dentition, no effusion of L ankle. Labs: low Hgb; WBC/platelets/mean corpuscular volume, WNL. What’s the dx?
Vitamin B12 deficiency
Henoch-Schönlein purpura
Meningococcal septicemia
Idiopathic thrombocytopenic purpura
You are correct. The patient had been eating only ready-made meals and no fresh fruit or vegetables for the past year. His vitamin C level was <5.7 μmol/L (normal range, 23-114 μmol/L), which confirmed the dx of scurvy. Perifollicular hemorrhages surrounding prominent hyperkeratotic follicles and corkscrew hairs, as seen in this patient, are pathognomonic of scurvy. Anemia is present in up to 75% of cases. Other clinical signs of vitamin C deficiency include gingival inflammation and bleeding, splinter hemorrhages, delayed wound healing, and joint swelling.

BMJ 2021;375:n2511